Lotus Elan

Heating Up When Stationary

PostPost by: William2 » Wed Aug 21, 2019 8:24 am

To answer a few questions, I have a 82 degree thermostat fitted, the metal fan is not fitted to the engine, the fan fitted is a modern unit that was fitted by the rad manufacturer and the fan is set to start up at 95 degrees and I have fitted a manual override switch.
As suggested, I think I will emulate the problem in my driveway and then pop the bonnet open to see if the temp comes down. I think Rohan and others have hit the nail on the head about heat causing it from the manifold. Looking at the layout the 2 centre branches of the manifold are close and directly underneath the head thermostat housing. As the car runs fine on the move I don't think changing the thermostat will make any difference. It would be nice to get the manifold ceramic coated but I don't really want to remove it. I might try and add some more lagging if I can get my hands in there.
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PostPost by: rgh0 » Wed Aug 21, 2019 9:08 am

I suspect the issue is radiant heat from the headers heating up affecting the sensor components outside the head / thermostat housing when there is no air flow in the engine bay to cool them. You're other temperature strips say its not the coolant getting to hot just the temperature sensor itself. I would try wrapping the sensor components where they screw into the head with reflective insulation wrap to see what impact that has

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PostPost by: MarkDa » Wed Aug 21, 2019 9:42 am

Yes if the radiator doesn't go above 90c then everything is working fine.
I suspect that you could spend ages trying to cool a very localised spot that's not causing any real problem.
Learn to live with it and accept that it's normal for your car :D
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PostPost by: 2cams70 » Wed Aug 21, 2019 10:42 am

That water temperature sender sensing bulb is submerged in the coolant. I'd be surprised if it's affected by radiant heat from the headers since there's constant temperature coolant continuously circulating around it. Different story about the temperature sensing strips however. They are stationary and directly exposed to radiant heat.

Did you check the radiator for built up silt and blockages? Did you check the fanbelt tightness? Personally I would not trust any form of sensor measuring engine temperature unless it's actually submerged in the coolant.

As a side issue why the heck did Lotus use a fluid filled bulb for sensing temperature rather than a standard electrical resistance one!!
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PostPost by: MarkDa » Wed Aug 21, 2019 10:56 am

I guess the availability of the smiths combined oil pressure and temp gauge and its widespread use in other sports cars of the period answer the final point.
Were electrical temp gauges that common in the early 60s?
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PostPost by: 2cams70 » Wed Aug 21, 2019 11:06 am

MarkDa wrote:I guess the availability of the smiths combined oil pressure and temp gauge and its widespread use in other sports cars of the period answer the final point.
Were electrical temp gauges that common in the early 60s?


All the same era Fords had electrical temperature gauges - even the 105E Anglia. Surprising then that Lotus chose to do differently. Maybe the combined gauge was cheaper than two separate ones!
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PostPost by: MarkDa » Wed Aug 21, 2019 11:34 am

It only required one hole in the dash and also gave an easy symmetry.
The extra room on the plus 2 dash produced a different solution.
It may not have just been cost - looks did play a part I'm sure
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PostPost by: gus » Wed Aug 21, 2019 2:33 pm

lotusfan wrote:Running the engine faster will increase the heat load, not improve the cooling.



This is simply not true

The answer has always been rev the engine up. You are not creating significantly more power and are increasing circulation.

If it is heating up while idling the fan is probably not right.

My +2 could always run till it ran out of gas in any weather with the [aftermarket] fan on and it has the small radiator.

retarded ignition timing

BTW 105 is not particularly hot

Is it continuing to climb or just sitting warm?
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PostPost by: lotusfan » Wed Aug 21, 2019 3:31 pm

lotusfan wrote:
Running the engine faster will increase the heat load, not improve the cooling.



This is simply not true

The answer has always been rev the engine up. You are not creating significantly more power and are increasing circulation.


I stand corrected, I was not aware of this note in the handbook.

To fully understand William2's problem it would be nice to know where the temperature sensor that turns the fan on is mounted.
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PostPost by: William2 » Wed Aug 21, 2019 4:18 pm

I have checked the ignition timing and its spot on and the engine idles and runs very smoothly with no flat spots, which is a good sign. Plugs are correct colour. As I had already mentioned there is no crud in the coolant as everything is new or rebuilt. The fan sensor bulb is mounted in the top hose where it attaches to the rad. I will try Rohan's idea of wrapping the sensor fitting in heat shield tape as I happen to have some. I did wonder if anyone had tried fabricating an ally plate heat shield that could potentially bolt to the top of the left hand grp footwell surface. I guess I am happy to live with this but I always like to try and solve engineering issues, part of the attraction of Lotus ownership!! My problem could be summed up as "thermal runaway".
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PostPost by: disquek » Wed Aug 21, 2019 4:56 pm

Rohan's point is about insulating the portion of the sensor bulb assembly that's outside of the engine. The high temps in the engine bay are adding to total temp of the sensor (inside + outside) and thus moving the temperature a little bit.

Mine (BDP) is right above the header. So I have it wrapped to the point where the wire wound capillary tube starts (basically covering the fitting and the nut).

If you have an IR thermometer, you could always shoot the radiator top tank and see how the temp differs from the gauge reading over time. This would tell you if it's a design issue with the gauge based on the external portion being heated, or an actual runaway condition (which is what I think it is) where hot air is being recirculated back through the radiator and reducing it's efficiency.

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PostPost by: William2 » Wed Aug 21, 2019 7:31 pm

I assume that the fan on the front of the rad should be drawing in air from the nose of the car and pushing it towards the engine??
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PostPost by: MarkDa » Wed Aug 21, 2019 7:46 pm

Yes.
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PostPost by: RichardHawkins » Wed Aug 21, 2019 7:48 pm

William,

Disquek is quite correct about stainless and mild steel. Stainless was originally used for its heat resistant properties.

A friend with a TVR Griffiths went through a similar series of problems. His radiator was also aluminium, and although the rad had not done many miles, it had a lovely coating of lime scale. Eventually he had the rad core replaced, and his problem was resolved.

Hope this helps,

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PostPost by: 2cams70 » Wed Aug 21, 2019 11:59 pm

William2 wrote:As I had already mentioned there is no crud in the coolant as everything is new or rebuilt.


No crud in the coolant does not necessarily mean no crud in the radiator. The Lotus twin cam engine was never designed for use with an aluminium core radiator. You can get all sorts of galvanic corrosion effects mixing different metals in the cooling system. The OEMs go to a lot of trouble to ensure the coolant formulation is correct for the types of metals used in the cooling system. You might get away with it in the short term but it may cause problems in the longer term.
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