headers and heat soak

[rdssdi]

I have a set of headers on my +2. I have been having chronic problems with high coolant temperature readings.

I have sorted everything and it appears that heat soak into the casting where the temperature sender is attached is being heated by the exhaust manifold. This may be the cause of the apparently erroneous gauge readings.

Has anyone with tube headers had this problem?

I would like to fashion a heat shield to deflect the exhaust header heat. Does anyone offer such a deflector?

I am reluctant to wrap the headers. Suggestions?

Bob

[Certified Lotus]

I'm getting ready to install headers on my engine and am having them coated by Jet Hot for that reason.

[carrierdave]

Not had an issue myself. Do you have one of those digital thermometers so that you can check the casting temperatures?

[rdssdi]

I had my headers Jet Hot coated.

Using a IR thermal gauge reads much higher than the rest of the engine and cooling system. Do not remember readings now. I assume well over 200 degrees.


If you do not have a high coolant temperature reading I may be incorrect in implicating the headers. I should construct a heat shield and see if it changes the temperature readings.

All else appears to be in order. I have the "correct" sender. The gauge voltage is 10 volts and with the test ohmic values in line the gauge reads the correct temperatures.

I will try a temporary heat shield and go form there.

bob

[69S4]

I've wondered about that for many years and still have the half constructed heat shield that I started some time ago in the garage somewhere. The short term test version (wrapping both the pipes and the head above them in "asbestos" insulation) didn't however make a significant difference so I didn't progress with the shield. The other (somewhat circular) argument was that it didn't appear here as an issue of concern so I thought it unlikely that it was a mechanism I needed to worry about. Let's see where this discussion goes now though.

[cal44]

I would try a heat shield. Form it and then apply and layer of heat resistant material on the thermostat side of the shield. The material I use looks like asbestos cloth, but is not. Of course an air gap between the metal you are trying protect helps.

mike

[Sea Ranch]

Lots of interesting products and systems for heat shielding.

This one looks pretty trick: http://www.zircotec.com/page/heatshield_products/97

Hope the problem/source of high readings is discovered.

I am planning on using the stock cast exhaust manifold, but coating it inside and out. I can see a number of places on the car that would benefit from effective heat shielding.

Randy

[JJDraper]

IMHO raised coolant temp very unlikely to be heat soak from the headers, otherwise we would all have the problem. Heat from the headers will have far more impact on other things such as engine mounts, bodywork etc. It will contribute to overall underbonnet temp, but the coolant sensor tip is in moving liquid, reflecting the head temp, not the thermostat housing above the header. I fitted the multi-layer zircotec sheet to the body to prevent heat soak on the fibreglass - works, but not convinced it was really necessary. I am far more interested in the header coating, but my funds where already stretched by the rebuild.. About 250quid to coat the set, including 'Y' piece when I asked. It really is the DBs, but expensive. Worked well in a friend's TVR (notorious for heat soak). You could almost touch the headers when the engine was ticking over - looked smart too.

Jeremy

[collins_dan]

Bob,
One question, when do you experience the hot coolant temperature readings? All the time? Just when sitting at idle? Only on hot days?

My S4 could run forever reading 175F regardless of outside temperature as long as it can keep moving. That said, even on the coldest day, if it sits at idle, you can watch the temperature rise. The speed of its rise is directly related to the outside temperature. I jet coated the new header and it certainly helped a bit. I have always wondered about a comment the Rohan made that at idle, an engine shouldn't be generating very much heat. Why does mine, and maybe others, seem to generate a lot of heat at idle? I have also checked the temperature of the headers with an IR reader, and even with the coating, it is still really hot.

Good luck with the heat shield experiment. Looking for good slave cylinder heat shield designs as well. Happy New Year to all. Dan

[Elanconvert]

not an expert but heat generated will be directly proprtional to rpm/load........
the engine gets hotter at idle as the cooling system is at minimum efficiency, i,e. little airflow through main cooling medium [radiator matrix]
if you want to see dramatic cooling, engage neutral on a long downhill run,,,,,,, i.e. high speed low revs/load..........

fred

[collins_dan]

All valid, but my question comes from the fact that most everyone that has this problem optimizes the efficiency of the cooling system first. So assuming all cooling systems are working at equal or even better efficiency, why does the problem continue? It makes me wonder the opposite side of the problem. Why do some engines seem to generate more heat at common low RPMs? Bob is thinking that it is the use of headers, and that a heat shield might provide a benefit, which might work. The exhaust side side of the engine is certainly hotter than the intake side, but I do wonder what options could be explored to make the engine generate less heat at low RPMs, while maintaining robust performance. Dan

[john.p.clegg]

Lean mixture?

John

[Sea Ranch]

I was thinking this, too. Could it be that the idle mixture is too lean??

[rgh0]

If your talking about total heat release from an engine it is at its minimum at idle.

If your talking about how hot an engines coolant gets or the engine bay gets that's much more complicated.

The slow burn and incomplete combustion at idle speeds may lead to a greater proportion of the total heat release coming out with the exhaust gases and this combined with low airflow in the engine bay may lead to the engine bay being hottest at idle.

Coolant temperatures may normally rise at idle if your have an electric fan and may become excessive if the pump or fan or radiator are not working correctly.

I don't believe normal headers affect the temperature gauge accuracy significantly as surely this problem would be more common. The TTR headers that rise up towards the temperature sensor location may have some affect but I have not noticed it on my Elan.

cheers
Rohan

[collins_dan]

In my case, and as I suspect in the case of many others, the mixture is good as is the performance of the fan(s). Is it possible that some engines just have greater issues with exhausting more incomplete combustion than others? Dan