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MG Midget and Sprite Technical - cooling stress test

Hi all
We've been having the first hot weather of summer this weekend. It was 24 oC here over the weekend. So I thought it would be a good opportunity to test the cooling system on my rebuilt midget. I left it idling and monitored the temperature. After about 15 mins it had reached 95 oC and was still albeit slowly moving up. The car has an electric fan which was running and the engine has 350 miles on it.
Overall I would much rather it stayed down at idle.
So what to do? one of the few things that I did not replace was the radiator so could it be it needs a recore? If yes can you fit on with an extra row of tubes?
Another option would be to fit the engine fan. I have one so would be a cheap option.
I guess what puts this into focus is my TR6 which stays cool as a cucumber even in boiling weather.
T Dafforn

Hi Tim,

Assuming the thermostat is working and not shut.

If a 1500 and you have not purged the deposits from the system then there may be considerable build up of crud throughout the cooling and heating systems.
Following Nigel's guidance. Back flushing, and repeating the process, works very well. Remove both the radiators and back flush. Flush the block several times and use a cleaning agent after that such as Holts.
Since carrying this all out twice last year (a few hundred miles between events) my 1500 has run cold without a thermostat and never overheated even on the hottest days in standing traffic.
I now run with an 88 degree thermostat, have a warm engine in no time and no overheating problems. I will either remove the thermostat or down grade the setting in a few weeks time for the warmest part of the summer.

Hope this helps,
Dave Squire 1500

Hi Tim,
I did a lot of research about a year (or maybe 18 months) ago into engine/underbonnet temperatures, (search on "science warning" if you like to look at facts and figures.......)

With the engine ticking over, and the system in good order and the electric fan sized to give with enough airflow then it shouldn't be running all the time, it should turn on and off at regular intervals.
If your electric fan is running all the time and the temperature is still slowly climbing then there is an issue with the water flow (thermostat not good maybe stuck halfway open or silted up system) or the fan simply isnt man enough ...

i have a graph somewhere (but posted on my old science thread) that shows a test where i just left my car running and you can see the effect of the fan coming in and out, giving a sawtooth pattern to the graph.
My ambient temperature would have been about 34 ish at the time...(its 37 today).

i have a datsun engine and toyota aluminium radiator with matched cowling and fan so your exact figures etc may be different but the principle is the same...

Andy Phillips (frankenfrog)

Is fan thermostat set correctly?
Is cooling system thermostat working correctly?
Is radiator clean internally?
Is cooling level correct? ie is it at at the correct level in the rad and the expansion tank when engine is running?
Any trapped air in the cooling system?
Is correct coolant employed?

Fitting an engine fan will not help you if the elctric fan is not keeping things under control.

Mark O

Also,,, forgot to add before.....

What temp is your thermostst rated at, you can get ones that are set for 95 degrees..... it could be that you have one of those installed and just need to change it to an 88 degree one..

And.. you need to check what temp the fan switch comes in at... it needs to start the fan at a higher temp than your thermostat rated temp otherwise the fan will run all the time trying to cool water that never reaches it...(depending of course on where your fan switch is plumbed in ....)
Andy Phillips (frankenfrog)

could it need a recore? yes very likely.
can you fit as 3-row core? again, yes, I have one in the racer; a good rad shop will spring the end tanks apart to accomodate a thicker core.
David Smith

Wow so many questions.
Engine has been rebuilt including a thorough cleaning of the block.
Thermostat is new as is the water pump. I think the thermostat is 86 or 88 oC and I can see it working. Eg on warm up the engine temp rises to about 88 and then dips momentarily as the stat opens and cool water enters from the rad. When driving the temp stays at middle on the gauge even when dawlding at in town speeds. If it gets hot when idling then it cools again if driven for a few mins.
I think the fan thermostat is set a little low as it tends to come in when the temp is a smidgen over half.
The fan itself is cheapo one of ebay so I wonder whether it is any good. It is acting as a pusher on the front of the rad and is definitely pushing.
Coolant levels are good and am running with the 50% antifreeze.
Cheers Tim
T Dafforn

O yes. No idea about the radiator. Came with the basket case when I got it and looked clean. Maybe needs a recore. 2 or 3 row? Have a chap here in kenilworth who just did my tr6 rad so perhaps a trip to him?
T Dafforn

I'd add -
. first though, have you finished running the engine in at 350 miles?
. second thought, is your gauge accurate?
. cleaning and scrapping out the engine block drain hole even though the engine been rebuilt an amazing amount of crud from the whole system can lie there
. external blockage of rad or passage of cooling air to it
. to follow the instructions in the Driver's Handbook fully for the refill of coolant to avoid hotspot air locks
. check electric cooling fan is operating in the correct direction, i.e. that the cool air is going through the rad in the right direction
. if you were running on idle could the fuel mixture be weak causing the engine to run hotter or timing well out
. bottom coolant hose collapsed causing restricted flow of coolant
. as well as coolant level what about oil level (secondary coolant)
. 95C isn't excessively high but if it was still climbing not so good
. stats are usually standard at 82c (180F)

if you want to just email for the very simple thorough cleaning system I use, which includes the rad, that I sent to Dave and he at one point thought it cooled his car too much so proves how effective it can be

costs very little and will help the cooling regardless

or run your engine in more and see how things go whilst of course monitoring the temp gauge

ETA: I didn't see your last two posts so you've covered some of what I've put here - check that electric fan is going in the correct direction
Nigel Atkins

sorry got timed out - I see you have checked fan direction

you could set the fan to cut in a little lower still say at middle

if you've no idea about rad it might just need a thorough clean as I detail in my notes

50% is a lot for the coolant but that's about the antifreeze properties rather than cooling so doesn't count here
Nigel Atkins

I agree with nigel some cooling fans have different vane angles for pushing or pulling the air, others just reverse the polarity.
mark 1500 Lights on at the end of the tunnel

The engine is probably still a little tight and had hoped to run it in while the weather was cool. It seemed to keep at a reasonable temp when the weather was cool. Would be interested in you cleaning details. My name is tim dafforn which is unique so if you search for my name online you'll find my email at the uni of birmingham.
T Dafforn

The fan is one of those reversible ones where you swap the fan over. Have to say that my rudimentary knowledge of aerodynamics makes me think that this isn't ideal.
T Dafforn

you may think that as the engine was rebuilt it'll be crud free inside but that might not be the case plus crud from the rad could have transferred to other parts of the cooling system

what oil are you using to run-in your engine?

what running-in instructions did the engine builder give?

depending on how it's rebuilt it could take many thousands of miles to fully run the engine in despite being able to drive it as normal, I'd not consider using a full synthetic oil for at least 6k-miles

one of the reason I bought my Midget was that the engine was rebuilt and supposedly only had 50 miles on it, now I can't know for certain that it only had 50 miles on it but I could tell the engine had been rebuilt, so it came as some surprise after doing a thorough system clean previously that when I had to drain the cooling system unexpectedly for a second time there was still some crud I could get out from the engine block drain hole

as you say the reversible fan doesn't sound ideal but it still may be sufficient you could try reversing it to make sure it isn't more powerful the other way

if your car is the one I'm looking at, white with different bonnet front end (you could put up a viewable vehicle profile to save guessing) then if it's fibreglass that'll hold the heat in more and the cooling aperture looks smaller for the rad - probably designed for racing round rather than static idling but I bet others with the same set up will say they don't have the problem

the longer days are here now you should be able to get more opportunity to get more miles in

when running in I'm a big fan of thorough oil and filter changes at vastly reduced intervals to get the crud out of the oil side of the engine too

email on it's way to you, let me know when you get it please
Nigel Atkins

Yes its the one with the monza bonnet. Inside th bonnet is a fibreglass airbox that mates with the front of the shroud. I've done some work to ensure the fit is pretty air tight between the airbox an shroud as I have found that ensuring warm air cannot recycle from the engine side to the radiator side is something many people neglect. Saying that I still have a 1 inch gap at the bottom which I ignored has hot air from the engine should rise. However is suspect some is recirculating so will fix.
I am running in with sae 30 with regular filter and oil changes. Was going to move to 20w50 at 500 miles.
The radiator was back washed before fitting.
Cheers Tim
T Dafforn

er, just to add one I forgot and not already mentioned -

. (fan) drive belt slipping
Nigel Atkins

ETA: I recommend a bit more than back flushing but not a lot more effort, good for an old rad you don't know the history or even a rad you bought new and installed

you also get cooling air go under the front of the car

go out and do 150 miles tonight whilst the good weather is still with us :)

viscosity chart below to give you some idea of SAE 30 compared to 20w/50 in 24C weather temp, little bits added together can give an increase in running temp

Nigel Atkins

Would love to do 150 miles tonight. Unfortunately am on kiddie duty.
Cheers Tim
T Dafforn

Tim it's always hard sifting the wheat from the chaff. Keep it simple, 3-row recore will sort it, especially as you already know a good rad place.
David Smith

always best to check to see if it's needed before replacing any parts or components but if cost isn't an issue and you're going to need more cooling than standard then yes recore the rad and just flush and renew coolant

one blunt self assured answer can be the right one but it's not a very scientific method to find cause and solution - and could be part of the chaff

email sent, if you don't want to follow it I won't be upset or offended as my ego isn't as big as some others ;)
Nigel Atkins

If the engine has been built to be more hp then stock....

Id definatly try an oil cooler 13 row, I had some problems right after my rebuild with sever heat under the hood and add a oil cooler and that made a huge freaken differance...I think its a good investment, for a new engine, because you over heat the oil, you wont have to worry about high engine temps agian


Prop and the Blackhole Midget

One thought from experience I had with a piece if scientific equipment that had an electronic power supply cooled with a water ethylene glycol mixture. When the percentage of E glycol was high i.e. around 33% the equipment over heated, when reduced to 20% it was OK. You say you have a 50% mixture which is quite high for the UK temperatures, with the heat transfer character of E/Glycol not being as good as water alone then that could contribute to overheating.
G.E Verney

as I remember it ethylene glycol isn't great for rubber hoses, tends to bloat them out until the elasticity goes (and with the quality of modern made hoses they don't need help to damage)

and I know for certain if, as my wife's friend did, you allow neat ethylene glycol antifreeze to pool in your spare wheel well in the boot then the bottom face of your spare wheel tyre will get eaten away

I like to pre-mix the neat antifreeze and water before it's put in the coolant system (or buy already pre-mixed) that way you know the exact ratio and quantity that going/gone into your system as the quantity is rarely as specified because of residue of flushing water or previous coolant
Nigel Atkins

In the summer months I like a 70 / 30 mix, then bump it up to 50 / 50 in winter

I think you need a decent % to avoid corrosion inside the cooling system

Prop and the Blackhole Midget

I run 50/50, even though there isnt the slightest chance of freezing here, in fact when Hell freezes over Thailand will be the next in line...

I was advised to do this by a friend who restores old cars for a living, he said especially if you have an aluminium head to use 50/50.... He showed me a head off a car he was working on and the white furry corrosion on the head which he says breaks off and clogs up the cooling system generally...

Ive got an aluminium head, water pump and radiator and need my system to be as good as possible to cope with the heat.

Biggest issue i think with cooling these cars is getting the airflow, in particular getting the air out of the engine bay so it allows more air to flow through the radiator. and this seems to be worse if you have a GRP one piece front end
Andy Phillips (frankenfrog)

Thanks chaps for all the input..
I think I am probably looking at a number of factors that together are tipping the cooling system over the edge..

1) hot weather
2) new engine running SAE30 running in oil
3) fibreglass bonnet
4) too much antifreeze
5) (perhaps too weak an electric fan)

Hopefully this weekend i'll drain the cooling system and remove the radiator and give it a flush (I may do a full system flush at a later date as per nigel's wonderful instructions). I will refill with 25% antifreeze and I think I may fit the engine fan I have... I know, the effect at idle will be minimal, but I think we are looking at a system which is just on the edge of functioning so every little bit helps right... And I can always remove it later. I will also complete the baffling between the airbox and rad. I'll then try and get out and put another 150 miles on the new engine so I can swap back to 20W50.
If the weather is looking crap, I may take the radiator for recon while it is out (hey... if I do that then the only bit that hasn't been rebuilt on the car is the diff..)

T Dafforn

as I've mentioned before I'd go along with your thoughts that it could be a number of factors

I wouldn't put too much weight to the 50% antifreeze mixture for the heat but if you're draining it I'd suggest going for a 33% mix rather than 25% to give more range for winter use and perhaps more concentration of coolant additives(?)

if later you do a more thorough system clean and overall then I'd suggest putting in 4-LIFE as then you can forget about the coolant/antifreeze for at least 10 years

my mate has a Toyota Supra with For Life from the factory build, he's no reason to believe it's ever been changed and the car is now about 20 years old, 5 or so years ago he got a dead battery whilst we were in France so left the engine running at idle whilst sitting nearby watching the other cars go round the 'parade' laps for about three hours with only the occasional rev up to keep the oil going the car sat at normal all that time and it was around 28C constant sun that day

I jump started his Supra twice from the Midget - but of those that saw it who would believe it was that way round
Nigel Atkins

Tim, I am not that convinced from your description that you have a problem anyway. Not for the UK climate, although if you do plan on spending a lot of time stuck in traffic in hot weather it may overheat.

The fan only really helps at lower speeds,, up to around 35mph. Above that, whether belt or electric driven it is really just there to make a noise and to hinder flow of air through the pressure fed radiator.

Air ducting ahead of the rad IS important though - you imply that it is incomplete a the moment.

Equally, you can overcool an engine too; less power, more fuel, more wear.
Guy W

Hi Nigel,
did consider 4-life, but there seems to be a general confusion over its use.. Bit like with silicone brake fluid... mind I have used silicon for yonks without the brakes failing, filling with water, rusting or exploding (as some would suggest would happen!!)
Also think the anti-freeze is a bit of a red herring but probably only need a marginal improvement.

Guy, kind of agree with you, for 99% of the driving I am doing at the mo this is not an issue but it does nigle..
Also agree about the engine fan and used to always remove them as a matter of course when I got a new LBC. However I bought a TR6 3 years ago which had one and didn't have time to remove it (elbow deep in midget rust at the time!). Then noticed that on the very rare occassions that the temp exceed the middle of the gauge in the TR6 I could lower it by increasing the revs by 500rpm. I really like this, as it makes you feel you have real control on temp..

Interestingly I had an elan that I never solved the cooling on despite a 3 row rad and cleaned out rebuilt block.. it would be fine in traffic, but over 70 mph the temperature would track the speed and at 95mph (on a track of course) it would be close to 100oC. Slow down and it would track back.. Really annoying

T Dafforn

don't confuse 4-LIFE with waterless coolants, it's not one of those

I've been using 4-LIFE in my daily use classics and brand new built cars including daily use ones for 20+ years and well into the hundreds of thousands of miles

its use is very easy, same as ordinary coolant, carefully, slowly pour it into a clean and empty cooling system so as not to introduce air bubbles perhaps

one of it's main attractions to me (other than its long life, high and low temp protection and change of colour if gases get in) is that it shows up even a small leak well and by the colour you can see if the leak is with the engine warm or after cooling plus CIS like you can follow the splatter pattern to track down the true location of the leak

Nigel Atkins

Hi chaps
Nigel ok gotcha. Wish I had known about this before I filled it with antifreeze.
Anyhow did some work on the car tonight. First thing I noticed was that with the electric fan on the air seemed to go through the radiator for 3/4 of the area of the fan while for the 4th quarter it seemed to be blowing in the other direction. Very odd. Anyhow took the radiator out and had a good look. On the rear of the radiator ( the side away from the fan) the fins where flattened in a quarter circular shape. Looks like it got skimmed by a fan at some points. The effect being that the air from the electric fan was being reflected back through the fan. Hence appearing to flow in reverse. So spent a happy 15 mins straightening all the fins. fitted the engine fan. But it just touches the oil separator on the chain cover. Its less than a mm on one blade so may just touch it with a file.
Got to clean the radiator now and re install
T Dafforn


Not sure what engine you have - if its a 1275 with a plastic fan there should be a circular spacer between the pulley and the fan - about 3mm thick - not sure about the steel fans.

richard boobier

1275 marina a series.
Got the spacer in place. It on just touches. Doesn't stop the fan turning if I turn it by hand.
T Dafforn

standard coolant is scheduled for changes every two years as the coolant additive wears out before the antifreeze parts so you'll soon get another chance to change to 4-LIFE :)

and if you have my luck you'll be draining the system well before then from some unexpected problem, particularly if you've employed p*ss poor specialist experts to do their bodge work

the "gently brush clean both sides of the radiator fins" should've picked up bent rad fins

I don't understand why you've fitted the engine fan when you already have an electric fan - the engine fan goes slow when it needs to go fast, goes fast when it's not needed at all and slows down engine warm up in cold weather

without a second thought for 30+ years you've put your faith in cars without engine driven fans but with electric fans that work off a thermoswitch (without the need of a bypass switch) without you even noticing

why add in the noisy old engine driven fan

but each to their own
Nigel Atkins

Hi Nigel,
Gave the rad a good brush. Quite a number of flies etc.
Regarding the engine fan, I do know what you mean. The system should be fine on the electric fan. Just interested as an experiment whether the engine fan will help push hot air from the engine bay. And I had it lying around.
Will probably remove it at a later date.
Hopefully there are not to many bodges. Only the ones that I have done as I am the only person who has touched the car during the rebuild :-)
T Dafforn

the engine fan, and electric fan, will not help push hot air from the engine bay, in fact quite the opposite they take the hot air from the rad and put it in the engine bay

unless you have bonnet or wing relief vents and/or powered extraction at the bottom of the engine bay then the temps will increase whilst stationary but this is controllable

have a look at Andy Phillips (frankenfrog), Thailand threads and posts on under bonnet heat
Nigel Atkins

With the electric fan on in my k I can feel the hot air coming out under the sills behind the wheels, and also from the back of the front wheel arch

I'm also running it on a decent nick standard radiator, and it refuses to overheat. Fan comes on at 100 off at 98 with a 12lb coolant cap.

The previous radiator had many dead fins and was leaking/seeping but it still didn't overheat.

I reckon it should be fine after a flush and you'll only need the electric fan on.
Rob Armstrong

Hi chaps
So added the engine fan ( controversial)
Dropped the antifreeze content and refitted the radiator with straightend fins.
Ran the car up to temp and purged the air.
Then left it running. Ok not a totally scientific test but the temp staus below 90 and the electric fan runs on a 30% duty cycle.
Interesting the engine fan alone seems to pull about as much air as the electric fan when the engine idles.
Obviously need to test this if the hot weather returns and will investigate removing the fan when the engine is run in.
But overall the objective was attained. I can now run the engine in with less worry that it will overheat in the summer heat.
Thanks for the help
Cheers Tim
T Dafforn

well done Tim you got the work completed just as the cooler weather hits in and with no more miles on the clock :)

soon you'll be able to apply for your Spridget fid..., er, no, best not put that, you'll be able to apply for your 'static Spridget' badge

if the electric fan is only as good as the engine driven fan at tick over then perhaps it isn't that good

later temp gauges done away with figures possibly so that owners would worry less or be lees critical or comparing the gauge reading in one car to the gauge reading in another

during the 23C weekend my car on its gauge showed about 72C when on the open road and at tick over the electric fan is set to cut in at about 82C (the N) on the gauge
I removed the engine fan when I fitted the electric fan four and a half years ago, 5 winters and 4 summers so far)

when ever temp gauge figures are mention I have to refer to the photo below to compare with my C-N-H gauge

Nigel Atkins

I don't agree that the engine fan is "controversial". It does the job it was put there for.

Sure an electric fan might well be more efficient, in that you can switch it on and off as you please/as required. However, there are plenty of A-series engines out there -- of the inline variety -- that don't overheat, and don't have an electric fan.

Mine has both. I fitted my electric fan when I used to drive around the southern Med a lot. I have a manual switch on it. The only time I ever switch it on these days, is to test that it still works. I'm actually thinking of taking it off now because my engine doesn't overheat. Hottest it seems to get sitting in traffic on a summers day in the UK, is circa 190. So I may be wasting hp, and a drop of petrol. How much I wonder? Bugger all I reckon.

If you have over heating issues, and you have a working fan ( be it electric or engine driven ), then concentrate on the radiator and or the pump and coolant.
Lawrence Slater

If your car does run consistently at 72 deg then it is being overcooled. It should be warmer than that for overall efficiency. Of course the gauage may just be wrongly calibrated

I think that the adoption of the C / N / H marking on the gauges was a cost cutting step to avoid having to manufacture and stock both Centigrade and Fahrenheit gauges for the different markets. I doubt it was really an intention to "dum down" for the average driver, although that is how the change was interpreted. The mechanisms are no less accurate, its just the dial is harder to glean much useful information from!
Guy W

Hi All,
Unfortunately am already a confirmed car fiddler. If I wasn't I would have bought a soft top modern merc years ago..
but I do take your point of getting the miles on it..
trouble I have is that since the midget restoration completed I have 2 LBCs asking to be driven, the midget and a TR6.. the TR has in the past got some good running e.g. weekend trips to Spa/lemans/lands end plus daily use (although my work commute is useless for running cars as it is only 5 miles!)

Now I have to neglect the TR to run the midget and get it worn in... hard choice and one thing that meant I was using the TR was the cooling of the Midget. That solved hopefully it'll get moving..
Might take it to prescott hill climb on sunday:-)

regarding engine or electric fan... don't really care so long as the car is cool.. I do however think I am suffering from a crap electric fan from Ebay..

Something I observed last night was that the electric fan didn't seem to kick the hot air out from through the front wheel arches like the engine fan did..

Instead (and very weirdly) the hot air seemed to be being blown out of the two vents in the front of the bonnet either side of the main radiator inlet (I have attached a photo of the monza bonnet to make this clearer).

The engine fan alone did not push air out through these holes...

My thought is that once the air pushed through the radiator by the electric fan it has lost much of its speed and then exits from the bonnet fairly passively. and because the fan is entirely covered by the shroud in the front of the bonnet hot air is free to spill out the front of the bonnet where it can be sucked back into the radiator.

Whereas the engine fan produces a more "energetic" flow on the engine side of the radiator with a clear motion towards the rear of the car reducing the amount of air coming out the front of the bonnet and ensuring more cool air is pulled into th rad...

probably talking Bo*&ocks

T Dafforn

the figure was as a guide as to where the needle points on my gauge transposed to Tim's gauge

it is a similar reading to other 1275s and the previous gauge showed the same

I think the cars are overcooled but that's only until it's stationary when things can soon warm up and things like fuel vapour locking on a hot day happen - I don't get these problems now

as I use my car during the winter I am experimenting with allowing the engine to get hotter but I've never seen anywhere a figure for optimum running temperature, in winter however low the gauge shows there's still plenty of hot air from the heater matrix so the 'water' at least can't be too cold

I can't remember where on the gauge my previous 1275 Spridget used to run at but the car certainly had less power than my present Midget and I've got 50mpg at a steady 50mph out of my present Midget so it seems reasonably efficiency but possibly I could get more and it's not near optimum running temperature

going up and down the Welsh mountain roads can have the needle moving to some worrying degree but all soon settles, the needle normally can be reasonably active anyway, moving on the gauge and sometimes the odd twitch/flick

I've no doubt you're right about the C-N-H gauge being introduced as cost cutting but it does mean that comparisons are more general rather than an owner worrying because his gauge shows say 70C yet his mate's gauge shows say 80C and it's been conjectured that oil pressure gauges were removed to stop the owners worrying about the reading especially in something like a V8 where at ticker over it might only read 10-25 so low on a gauge compared to four pot cars

I know when I had cars with oil temperature gauges I used to wonder about the sometimes very low readings, yet when I went out in a mate's Midget with one I worried about how quickly and high the needle went

information is great to have but you do have to interpret it and you can sometimes over analyse things rather than just enjoying the driving, mines not a precision car so small variances are to be expected
Nigel Atkins

you seem to want all your cakes - and to eat them

simple economics, of time in this case, the cost is what you have given up elsewhere - work, home, family, two classic cars

you're like Billy Bunter left in a tuck shop (howzat for an old reference)

I always fancied a TR6 until I got my GT6 and discovered the 'delights' of the separate chassis - car body went one way, chassis another, suspension another and the wheels yet another!

made the Midget feel so very together

but perhaps the TR6 chassis are better than the Triumph small chassis

I've never done a tour with a TR6 in, that I can remember anyway, done a few with a TR3a, in fact at least one tour with two TR3a, one was driven sedately and the other quite the opposite, nice to follow as they're not much wider than a Spridget
Nigel Atkins

(computer or site playing up)

ETA (quickly): the airflow might be different when on the move and it seems like your electric fan might not be the best
Nigel Atkins

Hi Nigel.
Bunter in a sweet shop. Very true.
TR6 also true. Chassis makes the car feel a bit wibly at times. But best long distance cruiser I have had. Easily keeps up with modern traffic on long trips and great exhaust note.
Midget. Also right. Felt much more together than most soft tops I have driven. Very nimble.
So actually very complimentary.
T Dafforn

thinking about it I've never ridden in a TR6, I'll have to see if I can get a seat in yours on a drive sometime - don't worry about your time constraints I'm excellent at organising other people's time being an expert with my own
Nigel Atkins

Could do if you ever come over for one of the Stoneleigh shows
T Dafforn

last two years I've helped out on the Sporting Bears Dream Rides at the Coventry Festival of Motoring

but you're safe I've got a prior engagement this year and I don't go to other purely static shows, I've been to enough of those to last me two lifetimes already
Nigel Atkins

I know that you use your car regularly and take pride in successfully maintaining it in good condition. So I wasn't meaning to criticise when I commented on the running temperature that you reported "for the open road". But I do think that 72 is too cool for normal everyday road use.

I don't think that the fabled "Handbook" actually states the ideal temperature, probably because there are too many variables like the nature of use and the ambient temperatures (including for overseas markets). But Vizard recommends around 85 degrees for water temp, commenting that at lower temperatures the oil is unlikely to heat up enough and that below 107 deg. it will rapidly deteriorate as combustion gasses do not evaporate off sufficiently. His recommended ideal for a road car is 85 for water and 110 for oil.

By comparison, I know that many modern cars are designed to run at 90 deg water temp. My Alfas were always very steady at 92, and if (when!) the steady temp dropped below that it was an immediate indication that the thermostat needed replacement!

People do worry that when the temp gets towards 100 that the car is about to boil over and seize. But of course this is not the case with a pressurised system which is designed to raise the boiling point. I think the 7lbs pressure caps on a Spridget raise the actual boiling point to around 113 deg (Not to be quoted as that is from memory - someone here told me the proper figure a year or so ago but my memory indexing system has deteriorated a bit since then!)
Guy Weller

Nigel Atkins

Wow, you're all absolutely right about the crud that comes out of a 1500 block. After I took my engine apart I had the block in a tray and saturated it with degreaser, pressure-washed it really thoroughly and oiled it up for storage. Then, before sending it to the machine shop I cleaned it again with the pressure washer really thoroughly. After the machine shop, same again and same again prior to reassembly. On each occassion more rusty crud came out even though it was running clean water at the end of each wash. When I was turning the engine right-side-up after fitting the bottom end, a load more (dry) gritty crud came out. As none got anywhere near the new bottom end I decided not to clean it yet again but I will flush it through like hell before it is started up. I've never known such a cruddy engine, amazingly it did not run massively hot when I drove 100 miles to my workshop just after buying it! I've now got a thermostatically controlled electric fan and an oil cooler. I'll set the 'stat to 95 degrees (eventually) and se how it runs.
N.C. Nakorn

I'm told it's even worse on some b engines with the block drain hole blocked solid

that why I stress the cleaning, flush/back-flush/flush-again of the engine block (whilst scraping out the engine block drain hole with a bit of wire during the drain and flushes), same for rad and heater matrix but also shaking them at the same time if they're out of the car

doing this and what you've done will have the cooling system cleaner than the vast majority of classics so once it done fill with fresh coolant and then forget about it until the coolant needs changing

then you can either just drain, flush and refill or with the engine, rad and matrix in situ flush/back-flush/flush-again all three again

if you have an oil cooler fitted then you also want a oil thermostat fitted otherwise often the oil will be overcooled

the numbers on my electric fan thermoswitch are far to minuscule for me to see so I just set it to where I want the needle to be on my water temperature gauge I realise the gauge might not be 100% accurate but it shows the same readings as the previous gauge so near enough especially as mine's just a C-N-H gauge
Nigel Atkins

This thread was discussed between 19/05/2014 and 02/06/2014

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