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MG MGA - mga overheating
| Hi all my MGA is suffering from fuel evaporation from the front carb bowl, I think, after I switch off after having been running the temp rises very steeply on the guage its then that I suffer with missing etc. i.e what seems like fuel starvation, I waswondering what the purpose of the horsehair pad was that sits onto top of the rad and whether that was put there to increase airflow through the rad and keeping the engine cooler in the first place mine is missing this pad, I also have fitted an 1950 cc MGB motor with a standard MGA exhaust and judging by the fierceness of the exhaust coming out I wondered if the back pressure was excessive and whether this would give a very hot motor, I'm probably talking nonsense so I will apologise now lol regards Gordon |
| g c pugh |
| Gordon - Are you suffering from vapor lock while running? What temperature are you showing when/if that occurs? - Ken |
| Ken Doris |
| I forgot to mention that one way to diagnose vapor lock, if at idle, is to raise the rpm and pull out the choke to richen the mixture. Cooler gas flow will then often lessen the stumbling/missing. |
| Ken Doris |
| I run a 18v motor and have no problem with overheating even with a supercharger packing the cyliners. Do you have a heat sheild on, get the felt pad, make sure your grill is open and the slates are not blocking air flow. Set your timing at 28-30 degrees at 3000 rpm. A lot of overheating is timing and not carbs. |
| jeff becker |
| When did you fit the 1950cc engine Gordon? |
| Bob (robert) I am turning? yes I once owned an MGWasp!! |
| Hi all engine was fitted by previous owner some years ago and he said he had problems, so he lagged the manifold and the back of the heatshield, my engine heats up very very quickly I meam within 2 mins of starting from cold, I think that this is due to having a standard 1500 exhaust system married up to a 1950cc motor therby increasing the backpressure and therefore the engine temp how ,else could it heat up so quickly. I wonder if others who have fitted the MGB engine have had exhausts made with bigger bore pipe and additional silencers, mine sounds very restricted almost choking anyway thanks for help so far regards gordon |
| g c pugh |
| Gordon I run an 1800 with the standard exhaust. I recently took advice from James at Bob West's and was assured that the original exhaust is ok. Interestingly, I recently had problems timing my engine with newly fitted electronic ignition - another story that I won't bore you with. However, I noticed that I was getting a massive blast and noise from the exhaust when the ignition was too far retarded, plus poor performance. All is sorted now. My engine certainly warms up very fast too, it does not like much choke and certainly not after the first couple of minutes maximum. The engine runs at a steady 175 in nearly all UK weather variations. I ran my engine without the horse hair pads for about 6 years, then fitted them and did not notice any difference whatsoever. In fact one of the pads fell off a year or too ago and I have not bothered to stick it back on. But back to your problem. I do not suffer your symptons despite having an MGB radiator expansion tank sitting right in front of the front carb that effectively blocks all cooling air to the front carb bowl. Steve |
| Steve Gyles |
| Yes Gordon I would expect your problem to be either poor cooling efficiency or poor ignition tuning set up. An engine produces heat as a bi-product of burning fuel. A poor exhaust will prevent the engine from burning fuel due to fuel being prevented from getting in, based on the physical fact that you can only get in what you can get out! I have seen many cars with these gimics in aid of cooling. Non appear to solve the problem. I have also seen many many cars with no cooling issues whatsoever and no get cool quick remedies. Simply clean radiators and well set up engines. |
| Bob (robert) I am turning? yes I once owned an MGWasp!! |
| Hell of a trip... Truro to Messingham..... good luck Gordon :-) |
| Rob Flint |
| Hi Steve did the reheat blast levels disappear when your timing was put right |
| g c pugh |
| Hi Ken vapour lock at idle after starting car a while afterswitching off car runs at 160 f going to 190 at idle climbsto 212 after switch off gordon |
| g c pugh |
| Gordon Mine will just that, on a hot day it can hit 230 deg after switching off. I find the recently fitted Kenlow fan keeps the whole thng cooler and works well to cool the system after stopping. The thermo syphon seems to work quite well. It seems you are having this vapour lock problem on a hot engine start-up. You should then use a little throttle to let more air and fuel in when starting. (Certainly no choke!) The poor running when hot could possibly be made worse if the mixture is too rich. We seldom tune up the carbs when the ambient temp is 30 deg, but it can easily happen on a hot day in the summer. Is it better in this cooler weather? Pete |
| Pete Tipping |
| Hi Pete thanks for that I do have kenlow fan fitted but only with manual switch so it doesn't come on after ignition switched off , now thinking about fitting thermo control, also owners in the states seem to very keen on fitting rad. shroud they say thissolves problem seen it on moss in the usa but not available in uk regards Gordon |
| g c pugh |
| Pete says "certainly no choke", which is what I suggested, based on what I had read on Barney's website. I used this "trick" several times myself, most notably in the Conch Republic parade in the Key West regional this spring. This works because it results in more gas to run into the floats , and that gas is cooler. Here's the link to Barney's page on this (towards the bottom of the page): http://www.mgaguru.com/mgtech/cooling/cool_101.htm - Ken |
| Ken Doris |
| Gordon In my humble opinion you should not be suffering regular overheating and vapour locks in the UK climate. I think you are making a mistake trying to treat the results of overheating rather than attacking the cause. I am siding with Bob and his wasp, and not for the first time. I bet you have either a partially blocked radiator or a poor repro unit. I made a point of having my replacement radiator to original specifications. Never ever had an overheating issue. Steve |
| Steve Gyles |
| Hi Steve, had a long chat to a very helpful gentleman at Bob Wests today, I now suspect timing maybe a primary cause , also checking rad cap, thermostat and air filter elements, evidently the 1950 cc engine is mildly tuned and should have K&N filter elements so I have quite a lot to check, also he reakoned the kenlow fan maybe not helping as it blockssome of the rad. He thought the radwas probanly okay as the temp whilst running remains at 160 even on hills andonly climbs to 190 at idle.He said the missing horsehair pad would only have avery small effect. regards gordon |
| g c pugh |
| Can I ask a silly question Gordon, at rest and ticking over the engine temp will rise until the fan turns on, if you do not have a mechanical fan still fitted. It would therefore be normal for the car to heat up until the thermostat started the fan or you started it by a manual switch. |
| Bob (robert) I am turning? yes I once owned an MGWasp!! |
| Hi Bob I still have original fan attatched the kenlow is only operated with manual switch gordon |
| g c pugh |
| Gordon I have my Kenlow fan with a manual switch only - the thermostatic control is still in the box! As it would shout at you under the bonnet and every time you whip out the radiator (a yoyo comes to mind) you should replace the little rubber seal that copes with the temperature sensor. I have wired my manual switch to the 'other' fuse which is still live when the ignition is off. I do have a master battery switch so it is not always live - saves cooking the coil this way... Taking it directly from the fuse with a sizeable wire keeps any voltage drop to a minimum making sure that fan spins flat out. I've got a fan shroud I took off mine as I found it ineffective. It came from the LBC Co., USA. Want it? As Steve says the repro rads are wrong, mine too. It's approx 1-11/16" thick, but I believe Bob West supplies a 2" thick unit, which maybe as the originals were. I always mix the anti-freeze with distilled water from the de-humidifier since the rad was new, to stop any chance of scaling it up. Now Steve I quite understand what you lot up there have to put up with in terms of weather mate; probably never known anything much above freezing I'll be bound! Now down here it kind of got up to something like 33 this year, so Gordon's old lump just might have got very, very hot. MG'ly Pete |
| Pete Tipping |
| Gordon my MGA travels around France every year and sees extremely high temperatures. I dont know if you remeber a very hot August a little while ago well I was travelling down to the south of France on the hottest saturday. Whilst my car stayed at 190 on the open road in each town the temp would rise to 205 ish, it did not boil and did rise if the engine was switched off. Since then I fitted a homemade electric fan in front of the rad with a manual switch that can be used with the ignition off. My original fan is still on and to date I have not been in such an extremely hot environment as that hot day in August so I have never had to switch on the fan. |
| Bob (robert) I am turning? yes I once owned an MGWasp!! |
| Hi Pete I didn't intend to restart the english civil war lol. My rad core is 2" thick and is a 3 core version, thanks for the offer of the shroud which I may well take up if all else fails. I have just measured my rad cap and found its not a long reach one and its only 4lbs. From all of this its not really the indicated water temp that concerns me but the heat in the engine bay which seems to cause the fuel evaporation in the front carb bowl which seems to get cooked by the manifold and the hair dryer effect from the rad. I think if my timing is sorted them the whole thing my just run that little bit cooler and I will be able to restart the car without having to wait for it all to cool down. gordon |
| g c pugh |
| Gordon You will have been speaking with James at Bob West's. I have always listened well to him. Good sound advice. Pete When my original radiator sprung a leak I exchanged it for one of Bob's reconditioned units. Never noticed the difference. You are correct about the 2 inch thickness of the cores. Il fait tres chaud sur le Costa del Flyde. Did you only manage 33 down there? Sounds a bit chilly! Steve |
| Steve Gyles |
| Hi Bob & Steve continuing thanks for all your ideas do either of you suffer from this problem on restarting the car when hot gordon |
| g c pugh |
| Gordon No problems starting at all, hot or cold. Steve |
| Steve Gyles |
| Gordon I don't have any problems with starting but going back to that extremely hot day the car did miss a little when the underbonnet temperature increased to a high figure. Obviously that was for my car a freak event but if the cooling system of a car is poor then high underbonnet temperatures can cause the effects you are experiencing. I think you really need to solve these heating problems first and then with those solved you will have a great car. One thing I often tell people with overheating problems is this. One of my race cars had a recored radiator fitted to it at the begining of a season. It ran great and cool all year. Thge next season was the same until a hot meeting in the middle of summer at Brands Hatch. the engine temperature began to climb to high and I had to back off the throttle to ensure a finish. On getting home I removed the radiator and intended getting a "Bigger" core put in. At my radiator specialist we took the rad apart to find the problem. In 18 months the radiator had began to block up with gung!! needless to say a simple clean of the internals solved the overheating! I mention this simply to demonstrate how quickly a "new" radiator can block up. As mentioned above I too now always use distilled water in my radiators. |
| Bob (robert) I am turning? yes I once owned an MGWasp!! |
| Steve Interesting one of Bob West's rads made no difference... Agree though Bob talks a lot of sense and such a fantastic amount of experience too. Have just wiped away the tears... Yes we only got 33 it's so cool here by the coast isn't it Gordon. Actually at those temps, the heat coming into car does make it an endurance contest. If the engine starts mucking about with those rear high ambient temps I usually give both tickover screws a tweak to bring up the tickover to get a bit more fuel through, speed up the engine fan and ensure it keeps running and re-balance later. The Kenlow has helped a lot with those situations. Pete |
| Pete Tipping |
| Hi Pete yes positively chilly down here in Cornwall during the summer, I havediscivered that I only have a short shank rad. cap so that wont help and Bob I think I might do as you suggest and flush the system, I have advanced the ignition a bit and that has improved the running a great deal. My only problem really now is the front carb bowl cooking the fuel after switch off giving me bad running on start up hot, although putting on choke briefly does help. gordon |
| g c pugh |
| Gordon How do you actually know the fuel is cooking only in the front carb? Have you got the flexible duct in place which goes from the large tube in front of the carbs down to the radiator duct panel behind the grill? Have you got a heat shield between carbs and manifold? Are the carbs balanced and set up correctly? Pete |
| Pete Tipping |
| Yes, the front carb will run hotter than the rear one when traveling at road speed. Above about 25 mph the air pressure cushion in front of the windscreen forces air into the cowl vent rather than out flow. Air flow then follows the curvature of the internal "scoop" to blow on the rear carburetor. If you open the bonnet after a hot run and touch the carburetors you will find the front carb to be noticeably hotter than the rear one. When you get stuck in stop and stop traffic, or shut it off for five minutes, the carbs get hotter yet. The front carb will be the first to suffer lean running from bubbling fuel. |
| Barney Gaylord |
| Hi Pete I'm assuming it is only front carb as it very much hotterthe rear one, I can hardly touch it without burning hand, funny though it only gets that hot after I stop or switch off, I have felt it immeadiatley after running at speed and it is fine, I have pipes in place and heat shield and manifold is even lagged, Hi Barney what you say sounds exactly what happening is there a cure or is it assomeoneelse has told me that its the bigger size of motor still with the 1500 mga bits trying to cope with it. gordon |
| g c pugh |
| Who told you that Gordon? |
| Bob (robert) I am turning? yes I once owned an MGWasp!! |
| Here are some things which may help some. The people who have done these things say it helps. I am inclined to believe these things may help, but I have not found the need to fiddle with it myself. http://mgaguru.com/mgtech/carbs/cb202.htm http://mgaguru.com/mgtech/carbs/cb203.htm |
| Barney Gaylord |
| HI Barney many thanks for pointing me in that direction, this morning I wondered if the pipe between the two carbs might be where my fuel is being cooked and that the front bowl might be getting hotter after switch off because there is no fuel getting to as it is being evaporated in that pipe, it sits right in the line of fire of hot air coming up from the manifold between the heatshield and the engine, so I have adjusted the pipe lower so its more out of the way of this blast a nd also bent the top of the haetshield more towards the engine so hopefully a little more of the heat isdeflected wawy from it. So far after a couple of runs I would have to say that I have not had the problem on start up and also the carb bowl whilst still warm is not half as hot as it was, we'll see how it goes gordon |
| g c pugh |
| Gordon I have just looked at my car. The armoured fuel pipe between the carbs sits about 2 inches outboard of the top of the heat shield. You have got something set up wrong there if the pipe is inline between the top of the heatshield and the engine. For starters, do you have the thick black spacers bewtween the carbs and the heatshield? Do you have any photos of your setup that you can post? Steve |
| Steve Gyles |
| Hi Steve my pipe now sits where yours does and lower down also bent top of heat shield more towards engine going to take shield off and bend top right down to top of manifold also fix some of that thermo nuclear heat resisting material to the back and also extend it past the ends of heat shield and below, so far what I have done and putting correct rad cap on seems to have solved most of the problems. again many thanks for your help gordon |
| g c pugh |
| Hi all do I speak too soon or isthe problem solved, I took heat shield off and bent thesection the sits at the top between the carbs over at an angle so it now sits under the inlet manifold and on top of the middle exhaust branch thereby almost totally deflecting the blast of hot air away from the inlet manifold, that will also help keep the linking fuel pipe cooler, I think what was happening was the the fuel was evaporating from that pipe on switch off which was leaving the front bowl with very little fuel in it which is why it was getting much hotter than the rear one because it was empty, anyway it is now a lot cooler to the touch and I have not had anymore problems on starting hot, famous last words I know, as a by product of checking I'm sure the proper long reach rad cap is also allowing the cooling system to regulate itself better, 160 running and not going above 190 on extended idle, once again many thanks to all who have once again helped solve,I hope, the problems regards gordon |
| g c pugh |
| Gordon the correct cap (extended as you refer to it) can only stop water from leaking out of the system and also hold pressure in the system to raise the boiling point of water. It will not reduce the temperature at tickover, that will probably be due to the fact that you may have timed the ignition better. The car remaining cooler and the heat shield will probably have eased your problems. |
| Bob (robert) I am turning? yes I once owned an MGWasp!! |
| Gordon I think you mentioned somewhere above that your rad cap was a 4 psi type, it should of course be a 7 psi cap which further raises the boiling point. When I got a replacement I found it was the same as a 1959 Mini cap. Peter |
| Pete Tipping |
| Hi Pete now have correct 7 lb cap on , seems better now , although Bob west thinks that maybe my front carb is getting very hot because its getting very weak at revs perhaps due to blockage somewhere gordon |
| g c pugh |
| Gordon I don't think your carb will get hot just because it's lean, it's the engine bit that gets hotter and might conduct more heat back... Very interesting point about the rear carb getting better cooled by the bonnet vent isn't it, this is certanly possible as it was known air went in from the top when the cars were new. I would have thought this would only apply at speed though and the petrol throughput should keep things cooler on the move. Must see what mine do after/during a run. Have just read through all this lot again - appreciate you have an 1800 unit, but have you checked you have the correct carb needles for your set-up? Both 1600's had No6 needles. As you will know a retarded lean engine gives the hottest results. Are your carb fuel hoses the S/S armoured type? Have read this armour helps to conduct heat away from hot spots. Bet your engine is doing better now in this cooler weather - mine laps it up! Pete |
| Pete Tipping |
| Hi Pete haven't checked needles but I was told that they had been matched to the engine, I have replaced the rubber washers that are on the banjo bolts that hold the bowls to the bottom of the carb body as one was loose and weeping fuel but the nut was as tight as it could go and Bob West told me that this might be some of the problem as the rubber goes funny with the fuel and can block up the lines and I must say that having done that it seems to have made quite a difference to way the engine idles and the fronr carb seems cooler but I have yet to take it on a run, if it ever stops raining gordon |
| g c pugh |
| Yeap it's all these little things that just get plum worn out! You just never know which bit is going to cause trouble next. Let's hear how things go. I have been having fun drawing up the 'Intake Exhaust Heat Shield' shown on Barney's site using Autocad, think I've cracked it too. The 4-1/2" centre section needs to be around 4-5/8" long, but it looks OK. Not sure if it can be viewed by anybody without the Autocad programme though... Pete |
| Pete Tipping |
| Hi Pete, will keep you posted on progress, I'm lucky I've got a local MG Center who are very expert on everything MG so they have been of great help too. Gordon |
| g c pugh |
| Pete There is apparently a free AutoCad viewer available at http://www.solidworks.com/pages/products/DWGgateway/eDrawings-Free3Dand2DCADViewerandPublisher.html The other option is to print the drawing as a pdf file. I am looking forward to seeing the final result. FWIW Larry 58 A |
| Larry Hallanger |
| Pete The best print from Autocad if it is to be viewable by those without Autocad would be .pdf files and the best Pdfwriter is the one that comes with Adobe Acrobat (not the Acrobat free viewer). Many people miss it because it is not included in a normal installation. You have to go to custom installation to find it. It can be added to an existing installation. It sets up a phantom printer that can be used by any program that would send something to a printer, just don't check the 'print to file' option when sending, the program will do it anyway. Another way to get a quick, but not as good quality print for those without Autocad would be to hit the PrtScrn button. Maximize the area you want viewed on the screen first. This will send the screen to the clipboard and from there can be pasted into any graphics program and saved as a graphics file. A two colour .bmp or .tiff will be slightly better than a .jpg for line work and if only two colours are used its not much larger. Because todays monitors generally have a much higher resoultion than the old 480X640 this is a better option than it used to be. |
| John DeWolf |
| and I thought I had an overheating problem but it appears I've stumbled onto another planet lol gordon |
| g c pugh |
| Hi Gordon I know what you mean - I'm just a lowly designer using Autocad - I don't know what these other guys are on about, seems very complicated... Pete |
| Pete Tipping |
| Pete Sorry.I was just trying to explain a couple of easy ways to turn an Autocad drawing into something non-Autocad people could read on their computers. If you like, eMail your .dwg file to me and I will convert it for you. Acad 2006 or earlier prefered |
| John DeWolf |
| Hi Pete and John I cant help being thick its ,something I've always been rather good at, come to think of it it's the only thing I've been good at lol. Pete it would be great if you could do that thingy that John suggested. regards gordon |
| g c pugh |
| John You should have drawings in your email... Pete |
| Pete Tipping |
This thread was discussed between 12/10/2006 and 23/10/2006
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