Lotus Elan

Cooling problem

PostPost by: Lordflashart » Fri Aug 11, 2017 4:29 am

Gentlemen,

Looking for a little advice.

My elan +2 is displaying some strange symptoms.
When first started from cold, the engine heats slowly and then continues to overheat and the coolant ejects from the overflow on the radiator.
However, I get it back to the workshop, and top the coolant off, the temp drops and then the car is fine, with a stable temperature reading no matter how hard I drive the car. It's done this twice now and I'm a little baffled.

The oil is clear and no mayonnaise, there is a little froth in the coolant, but the car had a very recent head gasket and this could be slight oil contaminating from the change, and appears to be reducing over time.

The second time, I removed the thermostat and tested it in boiling water and it appears to work.

Any ideas why it would overheat from cold and then be fine?
I'm hoping it's not a crack that closes up under head somewhere.

I'm getting a little frustrated with this engine, the car is sublime to drive, but so far the twin cam has been a total dog!!!

Paul
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PostPost by: StressCraxx » Fri Aug 11, 2017 4:46 am

Do you have access to a cooling system tester? Pump the tester up to 7 psig. The pressure should hold, warm or cold. A competent mechanic can perform these tests for you. Make sure you give him all the symptoms.

https://www.amazon.com/Stant-12270-Cooling-System-Pressure/dp/B0002SRGWU
Another method is a combustion leak tester.
http://www.lislecorp.com/divisions/products/?product=406
There is no cure for Lotus, only treatment.
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PostPost by: Lordflashart » Fri Aug 11, 2017 5:31 am

Thanks,

I'll buy a tester tomorrow.
Unfortunately in western Canada a "competent mechanic" is a rare thing. So I'm on my own.
I've built many engines over the years, but this one has me baffled. I've wanted a elan twin cam for years but after a few months of having one I'm seriously thinking of scrapping the whole damn thing and fitting a different engine!

Any other opinions? I've just ran the engine in the garage for half an hit and the temperature seems rock solid.
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PostPost by: vxah » Fri Aug 11, 2017 7:29 am

Just thinking here, you said you get back to the shop and top up the coolant and from then on it's fine? But you don't say if you let it cool down first? I ask this because normally if you remove the pressure cap with a hot engine it will "eject" coolant pretty damn quick, unless, there is already a lack of pressure in the system due to a faulty cap for instance.. is the pressure cap working ok?

Secondly the bottom of the thermostat needs coolant circulation around it when closed in order to react when it gets hot enough, if it's stuck out on a limb like the twink this can be an issue as the coolant could be boiling in the head but relatively cool under the stat so it won't open? I've always thought this was achieved by the heater circuit being constant with a mixed air heater box so that hot coolant is flowing past the thermostat on it's way to the heater... But I could be wrong here as looking at the small elan system it has a heater valve at the outlet from the head? If the valve is closed then it could cause the same issue but it doesn't seem to so, how does it function correctly and could this be why your engine boils before the thermostat opens? Once open of course coolant is flowing past the stat so everything is ok...

Back in the day the Vauxhall 1256cc engine had a little brass tube from the water pump to the bottom of the stat and it would block up giving the same issue you have! Got me thinking...
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PostPost by: Chancer » Fri Aug 11, 2017 9:09 am

Does your thermostat have a jiggle pin? If so is it free to move, if it doesn't then drill an 1/8" or 3/16" diameter circulation hole through the outer annulus.

Job done!
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PostPost by: vincereynard » Fri Aug 11, 2017 9:47 am

Interesting problem.

You say you have run the engine in the garage without a problem. So that is under a no load condition? That does suggest to me that the problem may not be with the thermostat. Although you could simple remove the 'stat and take it for a run. Once won't harm it.

Maybe it only starts to leak when it gets to a certain temp?

"the coolant ejects from the overflow on the radiator. " Is it actually boiling or ejected by excess pressure? Can you check the temp of the ejected coolant? Check the temp sender and thermostat accuracy? The temperature of the rad / heater hoses to check correct circulation? An air lock somewhere?

"but the car had a very recent head gasket" Did you do the change it or A.N.Other? If a "specialist" I would first suspect that if other checks are OK.

Don't dump the twink as you won't have a Lotus!

vxah wrote:Back in the day the Vauxhall 1256cc engine had a little brass tube from the water pump to the bottom of the stat and it would block up giving the same issue you have! Got me thinking...
.

Now that is interesting . Back in the early 70's I had a 1256 Firenza that would overheat whenever I went over 80. Flushing the system / pressure testing had no effect. I gave up in the end - now I wonder if???
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PostPost by: Lordflashart » Sat Aug 12, 2017 5:41 pm

Cheers Gents,

The thermostat doesn't have the jiggle pin, so I removed it completely and the problem disappeared.
I believe as suggested that there was an air lock under the thermostat causing it to remain closed despite the engine being hot.

I'll drill the thermostat as suggested and hopefully all is well.

I also pressure tested the cooling system and it held 20psi for 30 minutes without any pressure drop so it doesn't look like there are any leaks.
Thanks all!

Paul
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PostPost by: Chancer » Sat Aug 12, 2017 6:02 pm

I am confident that will solve the problem, FWIW its not so much of an airlock as a lack of circulation with the thermostat being at the end of a dead leg and the heat has to transfer slowly by conduction.

Having the thermostat upside down whereby the expansion bulb is on the cold radiator side will also give the same problem even with a jiggle pin hole, I'm not sure if the Elan set up would allow the stat to be fitted backwards but its another thing to check.
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