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MG MGF Technical - engine compartment temp.
|Having already had one head gasket failure I am looking to minimise the possibility of any more trouble.|
Looking at the F's cooling set up it seems obvious that the engine compartment is poorly vented. The cooling fan has a cut in temp of 85c but the fan on my car has only once cut in and that was not when the H.G.
failed. I would like to control the fan manualy or improve the flow of air over the engine by fitting some ducting underneath the car or deflector plates to perform a silmilar function. The apertures in the boot lid are a lot smaller than the area of the mesh exposed when the boot lid is raised. has anyone had a go at modification in any of these areas?
|Generalised information passed to me indicates that the MGF engine bay temp is an average of 30 degrees hotter than other K series averages. What the values are was not discussed.|
The side vents do little to increase engine bay airflow since the shape and positioning of them doesn't take advantage of any airflow patterns. However Roger Bunford and myself have been looking into creating an underside deflector which will raise the engine bay air pressure and hopefully force more hot air out of the engine bay.
We have set a plan to do some tests of the standard set up at different speeds with a number of engine bay temp readings, repeated with a deflector in place.
|I'm having trouble searching the archives and can't find a particular thread. |
I seem to recall a previous thread discussing testing the engine bay fan. Could someone please remind me on how to test this.
|I would also be very interested in your results Rog. I was thinking myself about fitting the K&N 57i pipes or similar (without the filter) to get more air into the engine bay. A scoop or the pipes only work when the car has forward motion obviously so i'd be interested to hear what the car is doing when people's HGFs have occurred....travelling at speed or stood in traffic? Paul or Rog, if the problem is heat soak when stationary is there any way of uprating the fan or reducing the trip-on temperature?|
One question, is there anyway of using a deflector that doesn't divert all the road crap in the air up into the engine bay?
|Engine bay temp is monited by the mems ecmwhen the engine bay temp rises above 75c the fan becomes operational the fan will continue to run untill the temp is maintained at 75c it is normal for the fan to operate for up to 8 mins after the ignition has been switched off If the engine bay temp rises to 90 c or above it will switch on the warning light on the dash when the temp drops below 80 c the light will extingguish I hope tis makes sense|
note the temps and timings are aprox and may change for different world markets
|mark the tech|
|At this stage the thoughts are for a wide thin deflector which will have little impact on ground clearance yet still be able to move reasonable volumes of air. This is based on some effective similar work done with a Championship wining car some 10 years ago. The deflected airflow is intended to be low speed so that it doesn't have the energy to carry water and other dirt very far. Creating a high speed and high pressure feed would increase that problem.|
The lack of a fan is deliberate, and will mean that air flow is applicable only with vehicle movement, probably above 20 to 25 mph. An alternative control for the engine bay fan to cover other times is quite possible.
I know that Paul Sharpe did hand a temp probe in his engine bay a while ago and reported the readings here. Paul, perhaps you can dig these out again.
|What is the usual direction of air flow in the engine bay, and how does air usually circulate around the major masses in the compartment? Knowing this may be helpful in knowing where to position the scoop to augment this 'natural' circulation. |
From my recollection of Paul's results, the lowest engine bay temperature was recorded in the area of the standard air intake- ie the lower rear portion of the engine bay.
just another idea, that Bruno thought on some time ago.
How about isolating the exaust manifold and flexi pipe with that for race cars availiable 'tempereture isolation band'.
It's no cheap material, but in the case that more air is blown from under the car this could help to decrease the temperature IMO.
|FIO the temp sensor is located at the top of the engine soi when the engine is running ok the temp guage works fine.|
If the engine is loosing water the temp gauge will not switch the fan on cos the temp is too low.
I am not so convinced that this suggestion is a good idea- imagine the incredibly high temperatures that would be confined in one small area with no obvious exit... It could be a recipe for disaster for a number of reasons. IMO Rog's suggestion is probably the best- increase the amount of circulating air to vent off the excess heat, and reduces the possibility of isolated hot spots that may contribute to HGF.
I will be completely amazed if I still have the temp readings. However you or Rob might still have them in your email inbox (i've changed computers twice in the past 6 months and haven't kept emails going back into last year).
As I recall, the highest engine bay temps were recorded at low speed (30mph) and stationery - like over 50 deg Celcius.
At 70mph temperatures dropped to 25 deg celcius (ambient was about 16 deg celcius).
Clearly there is adequate engine bay cooling at high speeds which makes me think that a forced air cooling system (with a fan) would be more beneficial for low speed air flow and cooling.
Rob is right in recalling that the lowest temps recorded in the engine bay were at the point where the standard air intake pick up is - and seemed to remain fairly constant in the mid 20's deg celcius irrespective of the temps in the rest of the engine bay.
Can you recall where those higher readings were recorded in the bay? 50 degrees is the sort of temps that V8 carbs can get up to in hot weather, low speed, when the fuel starts to vapourise and the engine runs like a dog as a result!!
I have to agree with Rob in believing that the internal temps under the exhaust wrap material will be too high and may even lead to some cracks in the metal. The other aspect is that poor constricting shape of the internal design of the exhaust manifold. This is very clear in the 4 into 2 join at the manifold to downpipe flange. I have another manifold which I have some plans to modify to hopefully reduce the constriction and ease exhaust flow. I do not expect this to be a power producing mod, rather a heat removing mod, with a possible minor power gain as a bonus.
|Surely the summer has arrived here in Portugal! Today it must have been 30ºc ... and this is just the begining! The weather forecast says the air temp will raise even more in the next days...maybe around 35-38ºc!|
Haven´t had HGF so far!!!! But i´m worried!
Engine bay temps:
- In traffic the engine bay fan always working!
- When cruising at 40-50 km/h the engine bay fans are still working, or if they are not working they will start working in the moment i stop!
- When cruising at full throttle in highway (235-240 km/h in the speedo) the oil temp rises to 140º in less than 5 miles!
- At 140-160 Km/h in the speedo...120ºc oil temp!
I always check the expansion tank.....i´ve got to add a little bit of coolant every day!
At 240 in the speedo what is the true speed?
at 240 it will be around 7k rpm!
At what speed "cuts" the 5th gear?
(the speedo touches the reset button of the counter and then it keeps reving until it cuts around 7200 rpm!)
I´ve heard from a friend of mine that today he saw a Porsche Boxter and he noticed the engine bay fans working too!
Since the Boxter mid mounted engine is much more hidden then MGF engine why doesn´t it suffer from overheating too?
|I am considering installing a 57i, but have grave concerns reference engine bay cooling when stationary.|
The standard air intake draws air from the engine bay. This surely contributes to air movement and so bay cooling when the car is stationary? Installing the 57i means engine intake air is not coming from the bay (part of the point of the 57i, to draw cooler, ambient air), therefore there is no longer any air movement into the engine bay (when stationary)(except natural flow from the hot air rising out of the bay).
Obviously, at speed, there will be a ram air effect, whatever the filter fitted.
Are there anyfigures of HGF against Filter type installed?
I think you have misunderstood the K&Nn 57i fitting.
The K&N cone filter is fitted directly to the throttle body and so draws air from the top of the engine bay whilst the standard system draws air from the bottom of the engine bay.
To help the K&N draw some cooler air the kit has two tubes that are mounted to direct air from under the car forward of the engine to the top of the engine bay in the vicinity of the K&N cone - so if anything a greater circulation is achieved and it is a fact that the bay is actually cooler. I for one have noticed that the engine bay cooling fan comes on far less since I fitted the K&N to my MPi.
many thanks for your answer. I did indeed have the wrong impression of the 57i fitting. I thought the extra ducting fitted directly around the cone filter.
I'll go for it then (insurance permitting)
My wife and i will be holidaying in Portugal next week, hope to experience high temperatures first hand. Not taking the F on holiday though :-(
|Hi Paul ....it´s very hot here...30ºc or + !!!|
If you come to Lisbon i would be very happy to meet you!
The high temperatures were recorded at the air filter. If I remember rightly, the temperature probe was fixed to the K&N cone.
I wonder what is being attempted here? This thread concerns engine bay cooling, yet Paul, in his original posting, is obviously worried about another HG failure. I wonder too, whether these two are necessarily linked?
I can think of several reasons why a cooler engine bay would be desired, for instance:
A gut-feeling that it should be cooler. I'm happy with this, people can act on whatever feelings they like. A cool(er) bay will bring less heat into the cabin and boot, will be more comfortable to the touch, and will probably extend the life of the electronic components housed there. That's not a bad return.
To get cooler air to the air filter intake. Another quite acceptable aim. Given Paul of Droitwich's surprising air temperature measurements I rather doubt if the temperature at the standard intake position (20+ deg C) could be lowered significantly, and any benefits would be negligible. Other intake arrangements will have their own air temperatures depending on the setup, and have varied performance differences too.
To postpone the day when the HGF appears. This is where it gets quite contentious. If this is the reason, why do we think that a cooler engine bay will delay or prevent an HGF? I suppose we could step back even further. Why, given Pauls temperature readings (I don't know where in the engine bay they were taken, but they were far lower than I expected) do we think that we need to lower the bay air temperature at all? Assuming we do, and assuming that we can produce some flow of cooler air through the bay, then what affect will this have on the engine?
The coolant temperature will stay the same. This is regulated by the thermostat in the return manifold, and cooled by the pipework and front radiator. Airflow over the engine will have no effect whatsoever. If there's a problem with coolant overheating then it's somewhere else, airflow won't solve it. The oil temperature won't be affected either, as it depends for cooling on radiation from the sump, which is already as near to the airstream as it practicably can. We have seen some very high oil temperature readings, of which more later.
Essentially the engine is not designed to be air-cooled. It's shaped like a brick with pipes sticking out of it. There's 110 kg of alloy and steel, 5 lt of oil, and some 5 lt of coolant (the other 5.5 lt are in the pipes). The temperatures in the combustion chambers are immense. To cool that lot by air would need a mass of surface area (i.e. fins) and a mass of moving air.
To get to the point - eventually - a cooler engine bay could have benefits but I don't think that HGF prevention is one of then.
On a practical point, the oil sump is slightly ribbed, probably more for strength than to increase the surface area and thus heat dispersion. Any deflectors which are in this area of the car should be very carefully sited, to avoid taking any airflow away from the sump. Perhaps the deflectors should cool the sump and not the engine bay? Someone else can argue about that.
|Someone correct me if I'm wrong...|
... but I though that HGF's were much more common on F's than on other cars that have the K series engines mounted "at the front" where they get more cooling?
I would suspect the problems are more down to the much longer runs of coolant pipes and the associated greater chances of vapour locks in them.
P729NLH -> as of today renamed to NNW 49
Thanks for the message but we will be a fair distance from Lisbon.
To return to my original posting, the reason for concern about engine bay temperatures was to suppose that if the engine can be kept in a cooler environment logicaly less strain will be put on the radiator/cooling system and in the event of a malfunction there might be a greater chance of avoiding a major problem.
You make some valid comments and I see the nature of this thread and others which connects engine bay temps and head gasket failure closer. I have said before that I consider the head gasket failure a symptom and not the cause. I feel that other failures have induced the gasket to fail, and this certainly does appear to be a factor that is more prevelant to the mid engined F layout rather than like engined 218iS, Vi and BRM 200 models.
One of the major influences to the gasket problem is the very limited volume of coolant in the engine block, 1.2 litres, (Rover figure) which means that the design advantages of very fast warm up from cold, can simply be translated to very fast coolant temp changes. This means that there is the prospect of some very fast temp changes once the engine is at normal working temperatures, upwards, if the right conditions exist!
One aspect of high engine bay temp is that many items other than the engine castings will cook, both during normal operation and after shutdown. The heat soak that occurs after engine shutdown is aggravated and items such as hoses, gaskets and seals will be subjected to much higher temps than in a FWD application.
Take a simple plastic inlet manifold to head face seal. Cook this continuously and sooner rather than later is starts hardening, cracking and then not sealing. Coolant leaks and we now have conditions where some very significant temp variations will apply within the engine and specifically around the liners and combustion chambers.
Clearly there are many other aspects that are affected and it is for these reasons I seek to provide a marked reduction in engine bay temps.
On the subject of achieving this goal I would refer anyone to the previous MR2 model, which has a couple of items on the underside that are of interest to F owners and perhaps ideal to mimic. One is a strong plastic shield that covers up all the under car lines. The second is a specifically designed air scoop which has a single function which is to direct air from the underside into the forward part of the engine bay. The resulting increase in air pressure inside the engine bay should then induce greater throughput of air and aid cooling.
I haven't been able to do anything other than examine a car on a ramp, but the intentions of the Toyota engineers is clear. They certainly wouldn't have added this extra cost item if it were not needed or at least beneficial.
The possible implications of heat sink have been mentioned a few times before: the F's configuration only has the bypass hose to offer any coolant circulation, unlike the front-mounted engines which have a fairly easy path to the radiator. To what degree this happens is not known to me. Yes, plastic will cook, as anyone who has attempted to dismantle some domestic appliances will know. I'm not sure whether additional circulation to the engine bay will stop this, as by definition it occurs when the car is stationary.
My journey home from work is some 20+ miles of A-roads, ending in town traffic and a mile or so of country lanes. My water temp gauge always shows just above the mark below half-way, and the oil temp round about 90 deg. Last week, and again yesterday, when I arrived home I switched the ignition on again immediately after turning off the engine, to see if the coolant gauge would rise as aditional heat soaked into the cylinder head. Both times the gauge would not quite reach its previous position, and remained there for some time, not showing any sign of the coolant absorbing any more heat (not at the tmperature sender, anyway). The oil temp gauge, however, fell to its lowest position within a few minutes. The engine bay fan was on, by the way. This is not very scientific, I know, but might have an interest to those who do such things.
What's puzzling me is why does the engine bay fan sensor trigger at 75 deg for the 1.8, and 85 deg for the VVC, and switch off again at 65/75 deg respectively? Why does the bay need to be 10 deg C hotter for the VVC (assuming that this was done for a reason)? I can't really think of a reason, except that with the higher power - and heat output - of the VVC the sensor was set higher to avoid excessive on/off cycling of the fan. And if the VVC can live with a high engine bay temp, why can't the 1.8? Anyone else have a clue?
|Could be so that the oil temp doesn't drop too low on the VVC when in traffic, as this would cause the VVC mechanism to disengage (as I understand it's temperature-triggered)?|
To have a guess at your last question: maybe the fact that the inlet manifold and accompanying gasket are different on the VVC (metal instead of plastic) make them more resistant to heat. The fact that the 1.8i (and NOT the VVC) have been prone to gasket failure there, with leakage into cylinder one, seems to corroborate this theory, doesn't it?
More generally: I have made what I find a very interesting (if completely un-scientific) observation on my current Lotus Elise 111S. Compared to my former MGF VVC (now owned by my brother), it is striking how much bigger the holes on the bootlid are on the Lotus: they are like two big A4 sized gaping holes with just a metal mesh to keep objects out. Add this to the fact (admittedly more relevant when on the move) that the side air intakes are much more efficient (witness the fact that air to the airfilter is taken from the airflow in the left hand side intake, and not from behind the engine) and you end up with what seems like a much better heat dispersion on the Lotus than on the MG. I have felt this by putting my hand above the exhaust manifold of the Lotus (right under the holes in the lid) immediately after switching off the engine (after a long drive) and then again after five minutes: the heat is great initially but after only five minutes it is already very reasonable. I seem to remember from the MG that the heat remained trapped for much longer - the exhaust manifold being burried far away from the tiny bootlid holes (I will get an opportunity to check this again tonight, going with my brother in his car - a much better long distance cruiser - to Charleroi to see the England game... :-)
Anyway, a more scientific comparison would of course need to factor in respective HGF occurence on Lotus's and MGs...
|Kes wrote :-|
>>What's puzzling me is why does the engine bay fan sensor trigger at 75 deg for the 1.8, and 85 deg for the VVC, and switch off again at 65/75 deg respectively? <<
I asked my dealer to check this on my VVC at its 3 year service last week. Testbook reported that the fan switched on at 102 and off at 96. This is apparently OK.
I asked for this test as the only time the engine compartment fan OR radiator fan have ever switched on is when my head gasket failed. Not even when stuck in stationary traffic after a motorway in 30 degree ambient temperature do they operate.
|"Not even when stuck in stationary traffic after a motorway in 30 degree ambient temperature do they operate."|
Is it??? If i were you i would be worried... my engine compartiment fan is always working: (VVC)
- when cruising at speeds below 50 km/h in hot days(currently 25ºc, but last week it was about 39ºc)
- when stuck in traffic in hot weather conditions too.
- when stoping in the red light when cruising in the city in hot days.
- It stops working after 2-4 minutes if i park the car.
- It stops working if i increase speed.
|I’m an owner of an MGF VVC-97. After reading this thread, I would like to give my opinion/points of view. Last summer I noticed that the engine now and then had a tendency to boil when idle for 10 minutes, or some times for a few seconds after turning off the engine. The water temperature gauge didn’t indicate overheating. I’m not sure if the water cooling fan was running at these situations. The engine was tested by my dealer, but no failure could be found (no electrical or circulation or leaking head gasket failure ). Later on, suddenly the head gasket failed. The renovation had no effect on the “after-boiling” phenomenon. So, what to do next? Last days we have done some tests of local temperatures (with laser instrument) on the surface of the engine including the coolant system. This measurements didn’t show anything but homogenous, normal temperature gradients, and normal water circulation. But we noticed that the water temperature sender started the cooler fan at 90 degrees Celcius (instead of 70-80 degrees which would have been optimal). Moreover, when we tested the temperature sender outside the engine, we established that it didn’t work at all. The water temperature gauge was also non functional. There we are today, and I’ve got one or two possible explanations of the HGF on my engine. Maybe all should at least test the water temp gauge, and make sure that the water cooler fan works to prevent expensive HGF. No I have to wait some month’s (previous experience from BMW in Sweden) for new temperature sender for the fan and for the water temp gauge shipped from Rover UK. That’s perhaps the most irritating thing with the present situation.|
I would appreciate some comments on my experiences.
I am worried - so I asked my dealer to look at it. I noticed that most MGFs run the engine cooling fans at certain times - but mine doesn't. The heat from the engine bay can be incredible.
How do you know that the coolant was boiling ?
There are at least 3 temperature sensors :-
engine bay air temperature - to the right of the plenum chamber
2 for the water (coolant) temperature, near the thermostat housing. One controls the temperature gauge, the other feeds data to the ECU (MEMS).
You wrote: How do you know that the coolant was boiling ?
Answer: You can hear and see air-bubbles running into the expansion tank.
Fred, there is a constant (almost!) flow of coolant from the long breather pipe into the top of the expansion tank when the engine is running. This, I think, is giving you the impression that the coolant is boiling. If the coolant were boiling in the exp tank then I think that the engine would be showing more obvious signs of distress and there would be heavy loss of coolant from the tank.
As has been pointed out, the sensor for the radiator fan isn't in the radiator, where any sensible person would put it, but in the coolant take-off manifold in the cylinder head, some couple of metres away. I can't remember the figures but the temperature to trigger the radiator fan must be higher than the thermostat opening temp (92 deg C?) otherwise the radiator fan would be on before the thermostat had opened, and that would be silly, wouldn't it? Sorry, can't discuss the other points at the moment.
|Any coolant running into the expansion tank after shutdown may also be due to a thermosyphon effect, but I think that this effect will be minimal due to the long coolant pipe runs.|
Today I have tried to get some aticle numbers but MG-dealers here in Sweden doesn't have any idea. Moreover I think the Swedish MGF-dealers (BMW) have an agreament to ignore all MG-owners. Can you help me with article number for 1) the temperature sender for the water cooler fan, 2) sensor for the water temperature gauge (both for MGF VVC-97)?
I have part nr MEK 100060 for the engine coolant temp.sensor (ie. the sensor for the ECU). I don't have a part nr for the sensor controlling the temp gauge.
oh b*gger. I've also noticed that the workshop manual says the cooling fan (meaning the front rad. fan) switches on at 102 and off at 96. So does this mean that my engine bay fan wasn't tested ?
Oh well, I've bought the stuff to measure it myself now.
Actually, my radiator fan did switch on today - is this a good sign ?
|Well, I am surprised.|
The air temperature in the engine bay - measured near the ECU's sensor - is typically 15 - 20 degrees C above ambient (about 25 dC today)
I didn't stop in traffic for too long - but only saw a temp of about 65. The highest temperature was immediately after I put the car in the garage - it had risen to about 72 before I switched off the ignition, and then rose rapidly (about 1 min) to 88 - falling rapidly after that.
So it appears that I don't have a problem - apart from being paranoid that is.
The only exact way to test the sensor for the ECU (radiator fan temp sensor) is by measuring the opening temperature (when the radiator fan sets on). You can do that with a laser beam thermometer on the block just where the water outlet from the engine is placed ( i.e.where the sensor is placed). My fan runs now and then, but the onset temperature is far to high (90 degree C). I don't think that this test is included in the regular mashine test, but in my opinion this moment should be obligate after a head gasket failure. This because the sensor is sensitive for the overheating that gives the HGF. This is my private opinion, and I would like to read comments from those professionals that only explains the HGF in MGF with a poor head gasket from Rover (like Mike Satur as I understand). I would not be surprised if many HGF depends on sensor failure. Moreover, I would like to recommend Rover to put in sensors less sensitive to overheating in future engines.
|Hi Fred -|
I'm not sure that we are discussing the same aspects of engine cooling. I believe the main cooling via the radiator is OK - it ain't perfect, but assuming it's free of airlocks, then it does work. A lower temperature thermostat could easily be fitted, if required.
My main concern was cooling within the engine compartment - which is air cooled. I still have a lot of testing to do, but this also looks much better than I thought.
I'm not convinced that there's a link between temperature and HG failure - if there was, then I would expect the sprinters etc. to be hit far harder, and this is not the case.
I don't, however, have an alternate theory !
|Ok here are my observations.|
Firstly the engine bay fan on my VVC never used to come on and initially I thought it was common for it not to 'work' on VVCs (as mentioned by many on this BBS). Eventually I tracked it down to the fact that the fuse had blown and even tho the car had been in for various servicing no one had checked (I guess u need to mention that there was a problem but I didn't realize there was a problem). Anyway the problem was fixed (the fuse was actually blowing repeatedly - trapped wire behind fuse box). Only recently has the fan actually operated. I guess these warm and muggy days have made a significant difference to the temperature. However it only comes on or rather I only notice it on after parking (got to turn the ICE down).
On another note I recently suffered HGF (quite some time after the fuse incident above, altho I'm not sure how much of an influence the non-blowing fan was on HGF). Previously I had added the Water Wetter treatment to the cooling system and noticed the water temp always settled at the half way mark. After the HGF the coolant was obviously replaced and now the water temp is usually one notch below the half way mark. My point is did the 'Water Wetter' have an effect of allowing the cooling system to absorb more heat and subsequently register a higher temp ?
By the way my HGF occurred at 42K miles.
There’s a lot of good stuff in this thread. At last we have some recorded engine bay temperatures (thanks Steve) to add to those done by Paul some time ago. I’d have done it myself except that I’m too mean to buy the kit. What exactly did you use, Steve? So far Steve and Paul’s readings show that when underway the bay temperatures are quite reasonable (to me, anyway). I wonder if it’s just a perception that the engine bay is hotter than it should be, due to the fact that it’s close to the seats and we’re often faffing around the boot? Can we take these two sets of temp readings as being typical of all our cars? At the moment I don’t see why not. Steve’s car is a VVC, I think Paul’s is too, but he might have been measuring another vehicle. Can we also take it that the 1.8 engine bay will be a little cooler? Maybe.
Fred, if you haven’t this data already the radiator fan switches on when the sensor reads 102, and off at 96 (second rad fan, if you have a/c, on/off at 108/103). The thermostat opens at 86 to 90, and is fully open at 102. The engine bay fan on/off temps have already been given. (All temps in deg C.) So your figures for your fan sensor could be OK, given some heat loss at the point of measurement. (I’m starting to sound like a manual.) How did your rad fan switch on if the sensor was duff? I believe that modern engines run hotter than their older counterparts to keep the emissions as low as possible.
Gaz, I did think seriously about using water wetter, and I believe Roger uses it in his engine. I didn’t go for it in the end for two reasons: I have an aversion to putting any additives in any of the liquids, and I think that modern antifreeze mixtures reduce the advantage that water wetter gives. According to the advertising blurb the water wetter will allow engine heat to pass into the coolant more readily by reducing local boiling, and thus be transported away from the cylinder head by the coolant circulation. The blurb says that if anything the coolant temperature will be reduced (by being dispersed more evenly), but the thermostat should maintain the engine temp at a constant level whether you have w/wetter or not. If the w/wetter was a good quality product I don’t believe it will have had any detrimental effect on the HG, or helped to cause the HGF. By the way my 1.8 temp at the gauge is always just above the mark below middle, as is yours, by the sound of it. I don’t suppose the garage replaced the thermostat, did they?
And furthermore.... someone mentioned that the output of the heater varies according to the speed of the engine: this must be caused by the coolant circulating through the bypass hose at lower revs, ignoring the longer heater circuit. Increase the revs and the coolant is forced to the heater. It explains why I can never set the heater control to a 'standard' setting, I'm always adjusting the thing up and down as I travel.
The 1.4 engine doesn't have the bypass hose but has a heater valve, so all circulation can be shut off when the engine is cold. In the Haynes manual for this engine it states that the coolant circulates around the head/cylinder when cold. With the bigger bore in the 1.6/1.8 engines the coolant can't circulate through the very narrow passages around the liners. Is this why we have the bypass hose? Does the 1.6 engine have the bypass hose, thus adding weight to the theory?
Looking at the invoice there is no mention of thermostat so I assume they haven't changed it. Anyway just noticed today that the temp gauge did not move from its rest position for about an hour (motorway driving) then all of a sudden it went on the move but got about a quarter of the way up the scale. Maybe my temp reading has been faulty all this time ...
|As i say and always said....my water temp gauge is always in the middle of the scale!|
Winter weather with 7-9ºc travelling in the countryside...in the middle!
Summer weather with 39ºc stuck in the traffic....in the middle too!
Winter in highway....middle!
Summer in highway.... middle!
Before the engine fan started to work...middle!
After the engine bay started to work....middle!
IT´S ALWAYS IN THE MIDDLE!!!
Weird isn´t it???
|I got the temperature readings via a module from Maplin Electronics (https://catalogue.maplin.co.uk/mainframe.asp)|
part nr YT99H - it includes the probe, and will measure up to 110 deg C. You just add one AA battery. Without adding any switches it will display temperature in deg C every 10 seconds.
|Hello again! |
Bruno V: I think the temperature sensor for the gauge in your engine is damaged, maybe by previous overheating. This can indicate an overheating problem that sooner or later eventually results in a HGF (by repeating stretching of the bolts in the top, leading to insufficient pressure on the head gasket, resulting in leaking head gasket (maybe the most common reason for the many HGF in MGF)). Are you sure that the fan is working ok? I would recommend you to test if the ECU is ok. This engine is as I understand, extremely sensitive even to marginal overheating.
Steve: Regarding the coolant temperatures. When the temp at the radiator fan sensor was 90 deg C (and the fan starts), the temperature at the outlet was 100-102 deg C. This will give us too low margins for overheating (especially when idle, because of the slower circulation rate), and about 15 deg C “overtemp” compared to the optimal working temperature for a modern aluminum engine. When the engine is placed in the middle (with a long distance to the radiator), you need more cooling margins than with a front placed engine I suppose. These temperature figures also shows that correct mixed coolant medium (boiling point 112-115 deg C) and the overpressure in the coolant compartment are extremely important in aim to prevent boiling and overheating.
|Sorry - I'm still not convinced that there's a design problem here. The water temperature gauge stays near the centre of the display because the cooling system has a large water capacity - which is a plus point.|
The mid-engine configuration does make it more difficult to cool, BUT it also separates the airflow through the main radiator, and the engine bay (the elise does it better though).
The fuel supply should not be a problem either - as fuel continually circulates, rather than just sitting in a (hot) float chamber.
The only issue that I've come across is when the car is driven very hard (track/motorway) and is then immediately switched off - allowing the engine bay temperature to rise quickly - but this is true in many cars.
I must get around to looking at underbonnet temperatures on my other car (a Seat) just for comparison.
Thanks for interesting discussion. To me, it's an on-going process trying to understand what happens inside the engine (and how to prevent next HGF). Today, I have got the new sensor for the temp gauge and will get the new ECU tomorrow. Before Monday, I will have answers to some of my questions. Will the coolant still boil when idle more than 13 minutes? Will the radiator fan start earlier with new ECU? Are there any points to recommend other MGF-owners (to prevent future engine failure)?
Just a little comment on your last letter: the temperature gauge messures the outflow temperature and is not affected by the total coolant volume. It would indicate the same temperature even if the radiator contained hundred liters of fluid. I still think that the best way to prevent HGF, is to prevent too high temperature variations, and try to prevent engine temperatures above 100-110 deg C. Remember that the cooling effectiveness drops immediately when boiling.
|If the coolant boils under normal (any?) operation, you've got a serious problem. Probably that the system isn't sealed and therefore operated at atmospheric pressure instead of the normal overpressure. Time for a change of coolant and the filler cap.|
as a new F owner, I am a little concerned about the number of HGF's referred to. Is this an inherent design problem (related to cooling or coolant flow) or all you all redlining at every opportunity. Please tell me its the latter.
I'm missing something here - exactly why are you replacing the ECU and temperature sensor ? The coolant should not boil - no matter how long the engine idles for.
As for points to prevent head gasket failure, I can only say :-
1) make sure the cooling system has no airlocks - use the heater !
2) make sure the car does not lose coolant
3) drive the last couple of miles gently, and don't switch off a hot engine - allow it to idle for a minute or so.
4) warm it up gently
I believe you could force the engine bay fan on by unplugging the sensor - but you will also get a warning light.
The coolant boils when idle, because the radiator fan sets on at too high temperature. When the fan is manually regulated (always on), there is no problem. In my opinion, the function of the ECU is incorrect. The main reason for this is (I think) previous overheating in hands of the former owner. The temperature sensor is replaced because it doesn’t give the correct information to the gauge (that information is essential for the driver). Furthermore, I know there aren’t any airlocks left in the system.
I don't want to repeat myself but, oh, what the hell. Fred, are you sure your coolant is boiling? I'm asking this because the flow of coolant returning through the breather pipe to the top of the expansion tank causes bubbling in the tank which looks like boiling. More significantly if the coolant was boiling then I'm sure you would have reported far more violent reactions from the engine, such as loud bangs heard and felt as steam tries to escape, the cooling system being very, very hot, and a considerable amount of steam being blown past the expansion tank cap. You have only reported bubbles in the expansion tank.
As for the engine temperature, the coolant circulates through the bypass hose (and the heater circuit if the valve is open) until the thermostat starts opening at 86-90 deg C. This is the lowest temperature of the coolant when the engine is running. I would think that the temperature recorded at the two sensors at the take-off point on the top of the cylinder head would be a few degrees higher, but not excessively so as the total coolant being circulated is, as Roger says, only 1.2 litres plus pipework. As the thermostat opens and closes to let in coolant from the radiator circuit the engine temperature should remain constant within the 90 to 100 deg operating range. Thus Bruno's (and my) car's temperature gauge will remain at the same point no matter how the car is driven as long as everything is working OK. Only when the thermostat is fully open, and the coolant is at or above the top of the temperature range, will the radiator fan switch on. There will be considerable heat loss from the long pipework under the car, so I'm not really surprised that the radiator fan doesn't switch on very often (apart from the first few weeks when new I have never heard my radiator fan switch on). Of course - another repetition - the rad fan sensor measures the temp of the coolant at the engine and not at the radiator, so the fan coming on or not reflects how well the engine temp is being controlled, not how hot the radiator is. As an aside I don't suppose all our sensors, gauges and thermostats are calibrated equally to the last degree.
Gavin, yes, we all red-line it. Well, not me, actually, as I'm more in the old roadster mode. There's a mass of info and opinion on HGFs in the archives for you to trawl through, if you can stand the phone bill. As for this and other threads, we just like to delve into every peculiar nuance of the car, and to chew over it endlessly. Just join in, and enjoy your car without worrying too much about it!
|Yep...i thing you´re right Kes....our F are identical!!! - I´ve never heard/saw/noticed my radiator fan working...even with our 40ºc of air temp here in Portugal. I cannot say the same about engine compartiment fan....now it is working almost permanently when stuck in traffic or travelling in the city!|
And i always refill my expansion tank 2 times a week because my coolant pipes are corroded and i prefer not to change then...better to keep the cooland loss under control!
...never had HGF...what about you Kes?
|There is certainly some interesting information on this thread. Returning to my original comments about the MR2's use of a specific deflector I have found that new this metal pressing is less than £20 so one is on order. |
My overall view is that the MGF engine bay is too restrictive and that too much heat is trapped for too long. The addition of the deflector, if it works, will be to increase the airflow through the engine bay and thus reduce the overall temp. Remembering that the underbonnet figures indicate that the F runs an average of 25 degrees higher. The source of this data is PTP who of course have considerable experience with K series applications!
Taking this information at face value I would like to achieve a substantial reduction whilst the car is in motion. Lower overall engine bay temps will provide a better working environment for many components. The peak temps after stopping should also be reduced as there will be less heat energy present when the car stops. Heat build up if stuck in slow or stationary traffic is another issue.
Another potential development route would be to modify the boot lid, which would need some additional water protection, to assist the removal of heat. Driving a 160bhp Elise this week on the test track (along with some other simmilarly tweaked K series cars) showed how much better heat dissipation from the engine bay was.
|So Rog...how do you explain the Porsche Boxter? The engine is completly trapped inside the engine bay...|
never heard about overheating or hgf!!!
I have no real idea, I have never examined the car. It is of course an issue that Porsche engineers will be well on top of, with decades of much hotter ruinning air cooled engines behind them. Are those side vents just cosmetic? Then there is an issue of the flat 6 engine with exhausts on the underside in airflow, crossflow engine cooling and no doubt other factors as well.
Having read the latest post from Dirk re another fracture of an exhaust, and also seeing cracked exhaust manifolds on MGF Cup cars at the Donnington meeting, Sunday, I can assume that some major thermal shock is causing tubular steel to crack. Airflow will have a significant effect on altering the temp ranges that these parts are subject too.
Bruno, at 10K+ miles no HGF in my MPi.
Many people with the K&N 57i filter kit (why 57i?) have fitted cool air induction tubes, and from their comments about picking up debris I assume that they pick up cool air also. This must reduce the temperature in the engine bay - has anyone measured it? Perhaps shorter tubes for a more general fresh air dispersal (with or without the filter) are an option?
I don't know about the new Boxter, but the Porsche air-cooled engines used a fan and ducting. Taking an extreme example - it's all I have data for - the flat-12 917 used a 13" dia fan driven at just under engine speed. This was no tiddly little device, but ate 17 bhp to push 2400 litres/sec over the engine. Now that would cool all our engine bays put together!
|The temp. readings earlier in this thread are for my car - a VVC with K&N + cold air tubes.|
Most of the readings are taken from the RH side of the engine bay - next to the ECU's temp. sensor.
I've also monitored the temperature by the main ECU on the LH side (ie behind the air tubes), and these are a generally a little lower than the RH side, with much lower 'highest' temps - about 50-60 deg C max.
I would guess that the air-tubes not only benefit induction, but also help cool the ECU.
|Nothing very scientific, but I have noticed that since fitting the K&N + induction pipes the engine bay cooling fan comes on far less often than it used to.|
So a couple of weekends ago (a hot one ) I sealed the ends of the induction pipes (very scientifically - stuffed some rag in them) and sure enough the fan was coming on and off like a whores draws. Removed the 'sealing medium' from the pipes and the fan only came on when reversing into and parking in my garage.
Now don't I just deserve an 'engineering award' for such contolled study.
|Graeme Bishko also recorded engine bay temperatures to determine the effectiveness of the cooling tubes.|
Highest temperatures were recorded after a run at idle- somewhere in the region of 50-60 celcius as I recall. On a motorway run at 60-70 mph, the temperature dropped (at the end of the cooling tubes) to arround 25 celcius aith an ambient temperature of 17 celcius...
Therefore the tubes are seen to work.
It'll be very interesting to hear Rog's experiences with the Toyota air deflector!
Curious that after hot weather testing in Arizona that Rover decided not to fit anything like this to the production car; perhaps there is more to the story than we currently know about?
Last year when we were all discussing this I was wondering if a deflector or wing could be fitted under the engine compartment to force cold air up towards the engine. If it was fitted to something solid enough it may also be able to assit with downforce.
The K&N (with cold air pipes) does reduce the running temperature a little, this can be seen on the water temperature guage.
I think just by making more slots across the boot lid and welding on a new longer cover to the inside could improve things as it would allow much more air to escape from the engine compartment. Maybe Mike Satur could build one if enough of us are interested.
I always thought of having proper scoops in place of the side air intakes, I understand that the Supersports style vents do catch more air than the standard.
I also notice that the MGF has enough space to take a larger radiator which could help things a little. An additional fan in the left hand air vent may also help with cooling. After this I suppose that an oil cooler would make a difference but this would need a thermostat to stop it doing too good a job.
Apart from this has anyone tried running a pipe from an Airco unit into the engine bay :-)
Tony, I'm a little confused again. How is the reduced running temperature with the K&N pipes shown in the temp gauge reading? If the thermostat is working OK then the coolant in the head/block will be maintained at a constant temp, whatever the driving or outside conditions, won't it? A larger radiator won't help with engine cooling either, unless the standard system is showing signs of being unable to cope.
If the coolant and oil temperatures are within the manufacturers spec, and we're happy with that, then there's no need to change it. If we want the engine bay temp to be reduced then lets go for it, but the two aren't necessarily the same thing.
I was just thinking about your intended undershield defletor and I was wondering about the gravel trap/cam belt escapade you told me Mr Gammons had at Silverstone. Seems to me that you could pick up some unwanted FOD (Foreign Object Destructive) and potential damage something . Also could this have an effect on the handling of the car, my thoughts are on that Elise we were playing with the other day and the simple venturi is supposed to be a fundemental part of the aero and handling package.
Just some thoughts mind!!!
I too have to follow the simple logic of Kes concerning the coolant temps. The rad, as far as I can ascertain, has more than enough capacity in terms of heat transfer to service not just the current specs but significantly more powerful versions that generate huge amounts of extra heat. Once again it is the thermostat which dictates the coolant operating temp.
Removing more heat from the engine bay is my goal here, this heat being totally separate from that which is transferred in and by the cooling system. Oil tempoerature control is a factor worth serious investigation for cars subjected to much higher average temps than found in the UK when these are used in a road environment. Cars used in competition where there is say more than 5 minutes of continuous flat out driving, which rules out most sprints and hillclimbs, can benefit from the facility of controlled oil cooling. (i.e. including a stat) This also seems to apply to the Steptronic where higher continuous rpms are a feature of the design of CVT.
Regarding the recorded temps we have already, my thoughts are that there is a clear division between the high temps during idle aand low speed work, even though the engine will not be producing that much heat, and the higher speed work. Higher speed does show a considerable increase in heat production but clearly the air movement currently available provides for a reasonably efficient removal of it.
Quite how this situation applies at higher speed where heat generation is increased so much more would be interesting to know. Even more so in the scenario of significant acceleration and braking where the engine performance is used, but the actual peak speeds are relatively low and only achieved for a short proportion of the total time the car is subject to this type of use. This IS a scenario that can be found virtually anywhere.
I now have the Toyota part and economy has obviously filtered into Toyota as the deflector is now a very light but rigid platic. Initial viewing of the deflector and car indicate that the fabrication of a suitable bracket(s) will allow mounting to the subframe via two currently unused holes.My general hope will be to increase the flow of air around the engine bay, with the lower threshold where useful flow starts lowered below the current point and increased beyond.
The shape and size of the deflector is such that when positioned the prime deflection will be on the gearbox side and less on the engine side. It will not extend towards the cambelt end and the standard wheels and wheelarch will create more of an issue with FOD than the new shiled will. Also the intrusion into the underside airflow will be quite small.
Following Steve's lead I now have a temperature display unit and 2m probe. Forget the oil pressure gauge, this is the thing to have. I never knew just how much I need to measure I didn't know I needed to measure before I bought the probe.
I've measured the engine bay temps in both my 1.8 and (old model) 214. There are of course differences, the 214's bay is 4" deeper and probably wider, and the engine only produces 103 bhp. Hmm, that's 73.5 bhp per litre compared to the 1.8's 66 and the VVC's 80. I digress.
It's almost impossible to get a definitive temperature reading, the display fluctuates according to traffic conditions which are rarely stable. However you can get a general impression. I fixed the sensor onto the throttle cable just behind the cambelt and just below the top of the engine.
The 214 was slow to rise from cold: town use was 35-40 deg C, A-roads (50 mph) 32 deg, motorway (80 mph) 32 deg, tickover up to 50+, and soak after stopping up to 55 deg.
The F rose much faster from cold, and changes were more volatile. Tickover temp, for instance, rose far more quickly. Town use was up to 45, A-roads 40, motorway 33 deg, tickover 50, and soak up to 56 deg.
I then fixed the sensor next to the engine bay sensor (no comparison with the 214). Temperatures were markedly higher, town up to 64, A-roads 48, motorway 37, tickover usually 60 but on one occasion up to 90, and soak around 80 deg.
There are inconsistances. On one occasion the stopping temp was 80 but the engine bay fan didn't come on, later in traffic the fan was on at 66, and when I arrived home the temp rose to 76 and the fan came on, dropping the temp to 62 in three minutes before switching off: the temp then rose to 70 and stabilised. I don't know whether the fan was on or off when the display said 90, the traffic noise was too loud.
Fixing the sensor next to the standard air intake hose produced readings of 35 in town dropping to 25-35 on A-roads (I haven't tried the motorway yet). Stopping temp was 38 with no rise.
So what conclusions can be drawn? Well, mine are that the F's bay temp is only a few degrees higher than the 214's (a 'normal' car?) when measured just below the top of the engine. Measured right at the very top of the bay the temp is considerably higher amd more volatile, and that's the stuff that comes out of the boot vent. The F's temp rises more quickly, and higher, probably due to the smaller space in the bay. As long as the F is moving at a reasonable speed (50+) the temp is fine. In all I'm happy with this.
If anyone else is tempted to do this then please keep your eye on the road, it's too easy to be distracted by the display. Also I would think that prolonged city use might send the temps quite a lot higher than my readings, I am fortunately out in the sticks.
|It's great to see another set of readings Kes.|
I note also that you're happy with the results.
The temp. module includes the facility to preset a temperature at which a fan could be operated, via a relay - this would also operate after ignition was off.
(MEMS doesn't monitor the temperature for more than a few seconds after switch off - unless it's already too high).
To get a lower switch on point for the fan, you could :-
1) wire a resistor in parallel with the sensor
2) move the sensor to a 'hotter' place.
So why does the VVC engine need a higher 'fan-on' temperature - especially since this occurs at/near idle speeds ?
This thread was discussed between 10/06/2000 and 10/07/2000
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