Lotus Elan

Engine running hot at idle

PostPost by: William2 » Sun May 27, 2018 4:31 pm

I took my S4 Elan out yesterday and got stuck in a traffic jam. The cooling fan came on at about 90 degrees but the gauge continued rising to over 100 degrees quite quickly. The jam then cleared and once on the open road the gauge went down to the usual temp of about 80 degrees. The outside air temp was about 24 degrees.
I have to admit I did not try pulling the heater knob on to increase the amount of coolant flowing round the system. The engine has been totally rebuilt with new water pump fitted and I have done about 1500 miles so far. I have fitted a new full width alloy rad with the single fan option. The exhaust manifold is stainless and having read about SS creating more heat in the engine bay than mild steel I have lagged the two forward branches but the rear ones would prove difficult without removing the complete manifold. I have just replaced to coolant and when I flushed the block etc no rust or particles came out. The carbs are fine with no acceleration flat spots and the tick over is very smooth even when the engine starts getting hot. Ignition timing all been set up correctly.
I am therefore surprised that I have this problem of temperature rising excessively at idle. Does it sound like "thermal runaway" in the engine bay due to heat from the manifold and other possible factors? Could the engine be getting hotter because of the low mileage? Should I repeat the test in the driveway with the heater in circuit to see if that brings the temp down? I guess in hindsight I should have maybe fitted twin cooling fans but I didn't think this would be necessary. I would like to overcome this particular problem as it is a worry stuck in traffic with a gauge going up and up!! Thanks for any help as always.
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PostPost by: 69S4 » Sun May 27, 2018 5:50 pm

I've had the same problem with my S4 for the 35 yrs I've owned the car. When I had the (narrow) rad recored it improved for a while but soon went back to its old ways. Lagging the manifold didn't help and neither did flushing the block or replacing / removing the thermostat or cutting a hot air exit hole in the inner wing or anything else I've been able to think of. Turning the heater on just slows the temp rise down but in a fhc it makes driving unbearable.

What does work is pulling the bonnet release so it pops up a few inches. The std electric fan will then pull the temperature down which makes me think the problem is getting hot air out of the engine bay when there's little natural air flow. The larger electric fan I've now fitted pushes enough air through that it'll keep the temp under 100C but pull the bonnet release (or run the car with it open) and the temp comes down very quickly.

How accurate the temp gauge is or what the actual boiling point of the coolant is on the gauge is hard to decide. I've spent hours in virtually stationary traffic with the gauge needle around 110C without anything untoward happening - apart from my stress levels boiling over - so there may be more reserve in the system than the numbers suggest.
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PostPost by: types26/36 » Sun May 27, 2018 6:11 pm

Just a suggestion, if the water pump has been overhauled at some time (in 35 years I would think so :lol: ) was the impeller pressed on far enough? I think Lotus say a gap of 60thou between alloy spacer and impeller ?? if the gap is to large may be the water circulation is not adequate while idling......just a thought :roll:
EDIT: actually without looking in the manual I think the gap is less then 60thou ......more like 25thou.
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PostPost by: RichardHawkins » Sun May 27, 2018 7:41 pm

William,

Have you checked the temperature gauge against a known standard such as a laboratory thermometer, or boiling water? I have spent most of my working life in the chemical industry, and have come across several problems where the plant runs well but we were worried by instrumentation that tuned out to be delivering incorrect information. One of my friends is of the opinion that the foam seal above the radiator is crucial and that if this seal is not good the hot air coming out of the engine side of the radiator will recirculate around to the inlet side of the radiator. There is also supposed to be a cover or shroud over the steering rack under the radiator to direct the incoming air through the radiator. My car was missing both the foam above the radiator and the shroud beneath.

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PostPost by: JonB » Sun May 27, 2018 8:04 pm

I think the bonnet foam strip comment is plausible.

I was wondering about hot air exraction from the engine bay myself (admittedly on a +2). What if a secondary fan was mounted horizontally under the car, behind the radiator, so as to suck air away from the back of the radiator. Would it make any difference (assuming it could be fitted / ducted)?
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PostPost by: 1owner69Elan » Sun May 27, 2018 8:30 pm

Another option if you suspect the gauge (probably not your problem, though) is to use thermal strips to check maximum temperature reached. This is what I did, in fact, and found that my gauge was bum.

img_9720.jpg and


http://www.race.tech/thermal-paint-strips/4587991257
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PostPost by: 69S4 » Sun May 27, 2018 10:08 pm

JonB wrote:I think the bonnet foam strip comment is plausible.

I was wondering about hot air exraction from the engine bay myself (admittedly on a +2). What if a secondary fan was mounted horizontally under the car, behind the radiator, so as to suck air away from the back of the radiator. Would it make any difference (assuming it could be fitted / ducted)?


I have wondered whether a 'puller' fan mounted on the engine side of the radiator would be more effective at moving air out of the engine bay but there really isn't much room there. I've run my car for extended periods both with and without the foam strip sealing the top of the radiator and the steering rack blocking strips and noticed only minimal differences - maybe a degree or two at cruise. I've also wondered whether heat rising from the manifolds disproportionately heats the area of the head where the temp sensor sits when the car is stationary. I made up a bolt on heat shield to protect the area but it made no difference that I could see.

At least once you get moving the temperature comes down fairly quickly. On my Honda GoldWing the fans are mounted behind the radiators but blow forward. If you're completely stationary it works well but if you're trickling in traffic the ambient airflow and the fan airflow cancel each other out at 15mph so the engine overheats very quickly. A really great piece of design that the aftermarket have been quick to supply fixes for. :(
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PostPost by: Andy8421 » Mon May 28, 2018 7:01 am

William,

Its mentioned above, but do you have the factory recommended two holes cut in the nearside inner wing?

It made a difference to my Sprint.

I replaced the rotten foam above my radiator, and replaced the very sorry original pressboard barrier above the steering rack with a fabricated aluminium panel - which doesn't sag when it gets wet.

Seems to have solved the problem for me.

Edit: Do you have the original air intake trunking in place? That leaves a big hole if it isn't there.

Good luck.
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PostPost by: Concrete-crusher » Mon May 28, 2018 7:46 am

Just an alternative thought but I found timing makes a massive difference to running temperature

That said it was hot yesterday :D

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PostPost by: JonB » Mon May 28, 2018 8:34 am

I thought maybe a row of PC fans under the gap between the engine and radiator might help, but it's not terribly standard. They are 12v but not robust. Might be worth a try.
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PostPost by: elanner » Mon May 28, 2018 12:41 pm

JonB wrote:I thought maybe a row of PC fans under the gap between the engine and radiator might help, but it's not terribly standard. They are 12v but not robust. Might be worth a try.


Perhaps it would be better to strap a pair of PC fans over the two holes in the left hand wing? This should help vent exhaust side heat build up. Strap up something temporary to start with, just to test.

The suggestions about proper water pump and temperature gauge operation seem worth pursuing, because why do Elans vary so much when it comes to cooling? My current Elan (without wing holes or bonnet foam) doesn't overheat, whereas one of my old ones (with wing holes and bonnet foam) habitually did. This surely can't be rocket science.

Logically, it seems to me that blanking off holes around the radiator and opening holes in the engine compartment provides little to no benefit when the car is stationary, because the air is, to a first approximation, not moving. Only when the car is moving do they optimize airflow through the radiator and out of the engine bay.

When the car is stationary the goal is to get some air moving. Which suggests that powerful fans are the solution.

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PostPost by: William2 » Mon May 28, 2018 1:05 pm

Thanks for all your advice. The answer is yes to everything. The bonnet foam and lower blanking panel is fitted and the air trunking is standard with a cone filter to allow more airflow at the front. The new water pump was done with the engine rebuild by well respected company. The temp gauge is new and yes I checked the sender in boiling water for accuracy and also it reads about 80 degrees normally with a 82 deg thermostat fitted. My car has the 2 holes in the engine bay.
As a last resort I like the idea suggested of having the bonnet open a few inches to expel the hot air build up and see if that helps. I think I might fit a small strap to prevent it opening too much. Might also try a couple of thermal strips out of interest. The comment about some elans running hot and others being ok seems to be true though and maybe I will never find out why. Interestingly no one has commented on fitting SS manifolds and extra heat but I know there are other threads on this.
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PostPost by: fjcoopelan » Mon May 28, 2018 3:24 pm

Hi

What was the air temp? Up to what air temp does your engine usually run around 80?

I've been battling with a running hot problem since my engine was rebuilt, radiator recored (thicker core and totally refurbished), thermostat and hoses replaced, etc. Gauge is fine. 1st issue was the timing and the car runs somewhat cooler now but it still gets hot in slow traffic and when stopped. Replaced fan with a larger pancake fan and installed an override switch.

The "normal" running temp is about 90 and I'm not pleased with this.

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PostPost by: richardcox_lotus » Mon May 28, 2018 6:00 pm

A daft suggestion. Is the fan running the correct way round ? If it came on but the temp continued to climb....

As an aside my Sprint always runs hot on the gauge, running temp is 95 and the (original) fan kicks in at 102...........according to the gauge. I’ve tried 2x otter switches and no change.

I tested the gauge against a kitchen thermometer a few years ago and it seemed accurate !

But there’s no steam, no water loss, idle is reasonably consistent so I’m convinced the gauge is at fault.

Regards
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PostPost by: joe7 » Mon May 28, 2018 7:58 pm

Just by chance what temp thermostat are you using?
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