Moss Motors, Ltd

I have a just rebuilt XPAG engine in a 1947 TC. I have driven it for only 400 miles or so and she is running hot all the time! The temp guage climes within a few minutes to 90 degrees, and sometimes peaks at 95 degrees. I also noticed that after driving for only 30 mins or so, if I stop to let her cool down, the temp continues to rise and a couple of times has gone over 100 degrees - then I can hear the radiator burbling, but no steam escaping!  Once she heats up to that temp it takes a good 15 to 20 mins to restart as I think the fuel is evaporating in the carbs due to the heat (I can hear the fuel pump clicking away like mad)

Today I simply turned on the car and left it idling for 20 mins. The temp climbed to 90 degrees within 10 mins, and by 15 mins was at 94 degrees. When I turned it off after 20 mins the temp climbed a bit to 97 before falling. This is clearly NOT normal. The radiator is full, and I topped up with a liter of water anyway, but made no difference.

 I have no engine knowledge at all. Is it the water pump The metal housing over the Thermostat get very hot, as does the top radiator hose, but I noted the lower radiator hose is not as hot, and remains fairly soft - does this indicate that water is not circulating?

 URGENT advice would be much appreciated.I did call the rebuild guys who said it was normal for a rebuilt engine to run hot for the first 1000 miles or so........however...this kind of heat when it is just sitting in the driveway for 20 mins does not seem at all normal. Ambient temp today was only around 22 degreess, so it does not seem to be the weather.

many thanks in great anticipation

JoeB,

It's true that a freshly rebuilt engine will develop a bit more friction related heat as it beds in, however it isn't usually too noticeable. First, is it running hotter on the gauge than it was before the rebuild? Second, is the same gauge in place? or has it been rebuilt? We need to determine if the engine is truly the same temperature as the instrument indicates. Find someone with an infrared instrument to scan the outlet neck.

Also, remember that this is a non-pressurized system. Some loss is normal from expansion, and it doesn't sound like you're exactly boiling over under normal running conditions. Are you using a mixture of water and anti-freeze? Your ambient temperature (72 degrees F. for us Yanks) shouldn't be promoting vapor lock, but the location of the fuel pump on T Series cars under the bonnet does indeed lend itself thereto.

Many of these engines have been converted to a modern themostat inside a traditional looking housing. Have you done this? Surely, in doing an overhaul you replaced the thermostat anyway, but I suppose it's possible it's not doing its job.

These motors are certainly not noted for running hot, but when we do a rebuild here in the shop we always renew everything in the cooling system. This includes the water pump, the aforementioned thermostat, and a boiling out of both the radiator and the block. If you've covered those bases, then do be sure to check the ignition timing, as a retarded setting will make this unit run warm for sure.

As a last resort, should none of the above prove useful, Empty the cooling system, then fill with pure water but for about a quart of antifreeze and a bottle of Redline Water Wetter or a similar product. This almost never fails to lower operating temperatures. Just remember that you have no protection in frosty weather. Good luck.

P.S. One last thing: A number of folks have discovered that you can fairly easily adapt a late MGB fan blade to this water pump, and that it has made quite a difference. I haven't tried it myself, but a number of people seem to have had success this way.

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Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

JoeB:  I have a '51 TD, which has the identical engine and cooling system as your TC.  The "T"-series cars were certainly not engineered to run well in summer heat.  A common error in filling the cooling system is to use a 100% mixture of anti-freeze (under the "more is better" theory), which actually reduces the thermal efficiency of the circulating fluid.  The XPAG is primarily a "thermo-siphon" design, with a marginal assist from the water pump.  The entire cooling system is "unpressurized", meaning there's a little standpipe in the radiator tank vented to the atmosphere.  If you top off the header tank, the resulting thermal expansion will blow surplus fluid out the standpipe (and all down the right side of your engine and side cowling).  Once the engine has established it's operating fluid volume, let it be.  Unlike the modern auto with it's pressurized cooling system, the XPAG's unpressurized radiator hoses will be "soft".

The so-called cooling fan is a model of aerodynamic ineffectiveness - the primary cooling for the radiator core occurs only when the car is moving at a good clip.  Like yours, if I just let my TD sit at idle for 10-20 minutes with the bonnet closed, it will indeed heat up to approaching the boil-over point.  Motorbill's recommendation for cooling fluids works great, and underline the part about no freeze protection.  Your description of the top and bottom hose temps is normal for this design.

Your diagnosis for the restart problem is spot on.  The XPAG engine with today's ethanol-enhanced fuel is very susceptible to vapor lock.  The no-cost fix is to prop the right side bonnet open every time you stop somewhere for a short time, say 30 minutes or less.  That lets the exhaust manifold (and the carb bowl just above the manifold) quickly cool down.  Other low-cost fixes include installing some non-TC standard tin flashing heat shields btween the manifold and the bowls, and/or installing the TF carb-intake manifold "thermal isolators", all of which reduce the heat transfer to the carb bowls.  Installing a after-market fuel pump back by the fuel tank will also help minimize vapor lock or cavitation of the standard Lucas unit in the engine bay.  In any case, it's all a matter of getting cooler fuel into the carbs.  You've probably noticed the engine runs really rough for 20-30 seconds after you restart it, then slowly smooths out.  Just the cooler fuel arriving from the fuel line aft of the engine bay.

Not to worry, all of the problems you've described are very typical for the XPAG-powered "T"-series cars.  All part of the British "character" of these wonderful little vintage sports cars! 

Joe - I agree with what has been said so far, with the exception of a couple of things.  First, there are several places where vapor lock can and does exist in the fuel system.  First is the inlet side of the fuel pump where the fuel is under reduced pressure because the pump is pulling the fuel from the tank.  The second place (and the one that causes the problem that you are experiencing) is in the passage between the bottom of the float bowl and the jet in the carburetor.  Installing an after market pump back by the tank will not overcome this problem (it would help the first area of vapor lock if it occurs there and is a great back up pump if the primary pump fails) because the vapor bubble that forms in this passage puts sufficient pressure against the fuel in the float bowl, and thus the float itself that to keep the needle valve closed hard and will not allow any more fuel into the float bowl.  Even the heat shield that Dick mentions doesn't help alleviate this problem (I installed one in our TD and still have the problem) because the root cause is the excessive heat build up in the engine compartment causing heat soak in the carburetors when the car is stopped and the engine shut off.  There are several ways to work around the problem.  1) install an electric fan that will run when the car is shut off until the heat is pushed out of the engine compartment and the under hood temperature drops.  2) Prop the hood open on hot days as Dick suggests.  3) pull the choke out and leave it out while the car is standing (this may cause the expanded fuel to be pushed into the intake manifold, result in minor flooding).  4) pull the choke out when starting the engine in an attempt to dislodge the bubble of vapor (this works fairly well for us).  These are all work just arounds, not a cure.  A lot of people have been fussing with this problem since the late 40s and so far the best thing they have come up with to my knowledge is to remove the side panels from the bonnet in the summer months.

Cheers,
Dave 

PS to Dick - I am sure you know this and the wording in  your reply was a slip of the fingers on the keyboard - Lucas doesn't make the fuel pumps for our cars (they do make some for late model Jags), our cars use SU fuel pumps.

 

 

 

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Cheers,
Dave
http://homepages.donobi.net/sufuelpumps/

Dang - another senior moment!  The stock "T" series fuel pumps are indeed SU units.  We found that the heat shields, thermal isolators, aft fuel pump, and aftermarket "Flex Fan" in lieu of the stock one significantly reduced the severity of vapor lock, but didn't eliminate it.  Raising the bonnet side panel was the only sure cure.

Actually, I did find a cure.  We packed up and moved from Colorado to the central Oregon coast, where the temp rarely exceeds the mid-70's, and usually in the mid-60's.  The XPAG appears to be thrilled to be back in a cool, sealevel environment.  It's never run better and not a hint of vapor lock

Dick - "Oregon coast, where the temp rarely exceeds the mid-70's, and usually in the mid-60's."

Score another one for the Pacific Northwest   We live in Bremerton Washington, right on the Puget Sound.  I think that MGs feel more at home in our weather.

 

E-mail me at SUfuelpumps@donobi.net and I'll send you a copy of a rather lengthy exchange on the T series TD-TF BBS that we had some time ago on the subject.  Some interesting information surfaced in that discussion and I have been trying to get the time do some further experiments with our TD.

Cheers,
Dave 

 

 

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Cheers,
Dave
http://homepages.donobi.net/sufuelpumps/

Dear All thanks for the rapid response and reassuring points. I am going to try the Water Wetter suggested...once I find it ....as I see it referred to a fair bit on the web, and take it from there since it seems it must just be a "running in" period in which the engine is running hot. Am told that it could take 1000 miles plus for the engine to settle down and then run cooler, and hopefully the Wetter will help the process Will keep you informed of progress. Thanks again!

I disagree that running hot is part of the game.  I know of several TCs and TDs including my own that can withstand mountain grades through the Mojave and Southern Nevada deserts in the heat of July without threat of overheating.  We drove right on through to Utah a couple Summers ago in 116-degree temperatures and never threatened to overheat!  My TC even runs a stock fan, and one of the TCs doesn't run a fan at all!  Admittedly the one without a fan could not sit idle for very long in those temperatures.

A common problem is in the thermostat housing.  There is a bypass hole which must be allowed to do its job.  Modern thermostats fitted to original housings often block off this hole or keep it on the wrong side of the thermo unit.  This disrupts proper circulation and causes problems.  I would suggest inspecting these parts carefully and returning them to stock condition.

I run 80% distilled water, 20% glycol coolant and a dose of Water Wetter.  Our climate is fairly warm compared to most of the country so more coolant may be a good idea for colder climates.

Best of luck!

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Joe,  Before you do to much, try adjusting your carburetors a little to the rich side.  With old style engines like ours, a small amount of the gasoline is needed to keep things cool.  Most people tend to adjust them on the lean side.  I did that last year during a major tune up.  The result was over heating, all the time.  I struggled with it all season untill discussing it with an MG friend who was a old WWII aircraft mechanic.  He suggested that I richen them up just a tad.  This year, back to running cool. 

bob 

Joe

I note the fact its a rebuilt engine, there's no chance you got the valve timing 'out' is there   [ Ive been there -  done that!] ?

On the fuel issue, vaporisation, I agree with what everyone has said, somewhere Im sure I read that butane was sometimes used to pep up the seasonal mix - and here's us trying to drive with unpressurised tanks!! I guess a  thing to note is that  what's left in the tank by Friday is likely to be a shade different to what went in on Monday .

The Octagon Club in UK are doing some interesting experiments with addition of  kerosene, about 15 to 1 and getting a cooler XPAG burn [and consequently less vapour lock??] BUT the question  will always be what CR are you running with?  I am not necessarily recommending it but I have a LCR  MGB and when I tried it the car seemed very happy I will certainly try it in my YB - - - - when I get it it on the road!!

Regards

steve

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To a man equipped with only a hammer, most problems look like nails

When I first got my 52 TD it had overheating problems.  We first took out the radiator and had it cored with a modern 3 row radiator core.  Then we put a 160 degree MGB thermostat in the housing and got rid of the original.  This all helped but it still got quite hot on long climbs.  I recently installed an MGB overflow radiator tank from a late model B and the car runs better then ever.  You run a hose from the radiator overflow to the MGB tank and install a 7 lb. cap.  You fill the radiator right to the top and the overflow tank to about 1/2 full.   I mounted the tank on a piece of slotted angle mounted on the radiator brace.  It fits there rather well.   I also discovered that the centrifugal advance was frozen so I put a bit of oil on the shaft to free it.  The car used to vaporlock when it was hot and became very difficult to start.  Since all the changes it runs cooler and restarts with no vapor lock even on very hot days.