Running Very Cool

[Longboarder]

Agree. As a pedantic purist I drive myself mad sometimes with searching out the 'technically correct' solution to any problem and hate it when I do a bodge which works round the problem. Always leaves me grumbling and grinding teeth to know I failed to solve it the 'proper' way.

Talking about cooling systems the age old invention of the thermostat is a brilliant effective low-tech solution to maintaining running temperature. If it's not working then I would be driving myself mad with why. Sure bypass the problem with a radiator blind pro-tem to enjoy the car but niggle away at why.

 

Nigel

 

P.S. Angling a radiator increases it efficiency!

[alanrichey]

From cold, start the engine, and feel the top of the radiator, if it starts to warm up BEFORE the stat opens at 88º (the one that you presently have in) then it proves that you have water flow through the rad before it should do. It should be cold until the stat opens, then will get hot quickly.

 

I don't want to get into a slanging match about this, but if I quote directly from the Rover manual "..Thermostat starts to open at 76C, and is fully open at 88C.." you will see the top of the rad will start to warm up well before the Stat quoted temperature.

[alanrichey]

P.S. Angling a radiator increases it efficiency!

 

Maybe up to 45 degs but I don't think so at 70 degrees

[Longboarder]

True. That might be a bit much.

 

Nigel

[Big Jim]

 

post deleted

Edited April 2, 2016 by Big Jim

[Guest lotusPaul]

Alan

 

Please don't get rid of the jiggle hole..its there for a reason..

In the school we teach two flows..cold and hot.

cold is start up to thermo opening..its circulating from headertank to pump- to block- to head- to thermostat-closed thermostat- bypass to pump. Continuing ytill warm

Small amount goes through jiggle hole and onwards to prevent air locks/cavitation.

hot flow is basically same up to thermo..thermo open- circulates to radiator- cools via air flow tho rad- back to pump.

cycle continues

if your running too cool then something is amiss..

I don't know the way you are plumbed in but please post if it's different.

In essence the thermostat is constantly opening/closing to maintain the engines optimum working temperature. So if your constantly running cool, or hot, then you may have an underlying issue that you are essentially skirting around and limiting efficiency of the other components within your own system to mask..therfore NOT actually solving the original problem.

 

I'm happy to discuss

 

Paul

[Guest lotusPaul]

Alan

 

Please don't get rid of the jiggle hole..its there for a reason..

In the school we teach two flows..cold and hot.

cold is start up to thermo opening..its circulating from headertank to pump- to block- to head- to thermostat-closed thermostat- bypass to pump. Continuing ytill warm

Small amount goes through jiggle hole and onwards to prevent air locks/cavitation.

hot flow is basically same up to thermo..thermo open- circulates to radiator- cools via air flow tho rad- back to pump.

cycle continues

if your running too cool then something is amiss..

I don't know the way you are plumbed in but please post if it's different.

In essence the thermostat is constantly opening/closing to maintain the engines optimum working temperature. So if your constantly running cool, or hot, then you may have an underlying issue that you are essentially skirting around and limiting efficiency of the other components within your own system to mask..therfore NOT actually solving the original problem.

 

I'm happy to discuss

 

Paul

[alanrichey]

This thread has become so contentious I was going to shut up and go back in my box. But maybe one last thing. No-one has yet explained to me why my theory is incorrect.

 

We have to remember my thermostat doesn't suddenly snap open at 88C and snap close if the temperature drops to 87C, it is a very gradual process over 10-12C. As I see it, my engine starts to warm up until the thermostat starts to open at 76C (Actually if I look carefully at my graph I think that happens at 73C, probably just down to manufacturing tolerances). At this point water starts to flow through the thermostat and is cooled by the air flowing through the radiator. Now, if by the time the temperature reaches 78C the thermostat has maybe opened about 30% and the resultant flow of water and the cooling via the radiator is sufficient for the system to reach a steady state so it remains at that temperature. What I have done by masking the grill is to reduce the amount of cooling air going through the radiator so that the thermostat is forced to open a bit further to allow more water to flow through the radiator and so the steady state raises to about 85C.

 

Where is the flaw in that logic ?

[kevin the chicken]

I wondered what the jiggle hole was there for now I know! My stat on my redtop didn't have one so I drilled a small hole to allow any trapped air to escape upwards.

The point that i remember is that the workshop manual for my engine calls that stat a 95 degree one but if you look at the technical specifications it states that it is not fully open until something like 107.

Like Paul I have always understood/ assumed that the stat continually opened and closed therefore keeping the temperature fairly constant unless the radiator was blocked off in which case it may overheat. Obviously not in your case though.

You are lucky that you have an accurate recording of what is going on via your ecu.

Don't go back in your box Alan, we need you. Every day is a school day for me.

[alanrichey]

OK, you asked for it so here it is

 

 

Obviously everything in black is a standard core system used by all cars. The Green pipe running from above the thermostat to the top of the expansion bottle is standard Rover design and allows the coolant to expand into the bottle The part of the red pipe that runs from underneath the thermostat to the expansion bottle is also Rover standard and I assume that is the return path for the coolant when the engine cools off.

 

In a normal Rover the rest of the red pipe feeds the ancillaries (Heater, aircon..) but in the Superpec it goes across the top of the engine and into the top of the radiator. I have no idea why, but the presence of the bleed valve leads me to believe it to assist in filling the system.

 

And I have absolutely no idea what the blue pipe on the left is for. Maybe the radiator (anyone know what it came off ?) had a spare outlet on the opposite end of the top of the radiator to the top hose, and the expansion bottle also had a spare inlet so RHE just decided to join them with a tube ?

 

That's all I can figure out.

[Longboarder]

Can you show direction of circulation through pump/block? (I assume the pump sucks back from the rad and pumps water into the block but that may be wrong.)

Does the thermostat close off the red pipe as it opens flow to the black pipe to top rad?

Which pipes in the expansion bottle are open to air or under water?

Physics suggests that an overcooled engine is allowing too much uncontrolled flow to the radiator.

Looks like some duplication of circuits allowing thermostat bypass.

 

Nigel

Edited April 2, 2016 by Longboarder

[Big Jim]

post deleted

Edited April 2, 2016 by Big Jim

[alanrichey]

Can you show direction of circulation through pump/block? (I assume the pump sucks back from the rad and pumps water into the block but that may be wrong.)

 

The Rover manual agrees with you, pump takes water from bottom hose and pumps through engine block and inlet manifold before coming out underneath the thermostat.

 

 

Does the thermostat close off the red pipe as it opens flow to the black pipe to top rad?

 

No, Red line appears to be permanently open

 

Which pipes in the expansion bottle are open to air or under water?

 

All under water, particularly when engine running when expansion tank appears to be full.

 

 

Physics suggests that an overcooled engine is allowing too much uncontrolled flow to the radiator.

Looks like some duplication of circuits allowing thermostat bypass.

 

Sounds logical. I guess I could try temporarily blocking the red and blue lines out of the top of the radiator,

[alanrichey]

Hi Jim

 

You yourself had this problem previously hence changing pressure caps then removing the stat. agreed.?

 

 

Not really. I think my previous overheating problems were actually caused by a leak of the coolant under pressure from a dodgy connection. And as the water level dropped, that caused the temperature to rise and the pressure to rise, and at 13psi she started dumping water overboard and the situation just ran out of control. And it was during this period I removed the thermostat to try and cure the problem. It then came to a head when I fitted the 20psi cap and in that case instead of the water being dumped overboard the pressure just kept increasing and it blew the dodgy joint apart (In the middle of the A6 ). So I fixed the joint, and that was when she started to run very cool (stabilising at 62C). I assumed that was because of the lack of a thermostat so put an 82C one in and she then stabilised in the low 70s. So moved to a 87C stat and then she stabilised in the high 70s.

 

So I think we can safely ignore all the previous problems as a red herring, and assume that I now have a cooling system working as it was originally designed to run (Whether that is a correct design or not) and start from that point.

 

I should also clarify that I am not using the in-car temperature gauge for this work I am analysing the output of the ECU as it is much more accurate. And as a precaution I have already changed the ECU temperature sensor with a spare one, and they both read identical values. So I think we can safely assume the temperatures I am seeing are genuine.

 

But I do take the point about water going into the top radiator when it shouldn't, so unless someone can explain to me why those extra pipes are there I will try temporarily blocking them off.

 

And thanks for the offer to chat but first I will run all those test you suggested to make sure everything is opening/shutting/warming up as it should. Might even treat myself to an infra-red measuring gun That way we may be able to eliminate other things.

 

But at the end of the day I am still waiting for someone to point out the flaw in my logic that says that having fixed everything I now have a very efficient cooling system and that at 78C with the thermostat partially open I fulfill the equation:

 

Heat dissipated by radiator = Heat created by engine.

 

so she just doesn't get any hotter. And the only way get her to run hotter is to reduce the left hand side of the equation by blocking off part of the radiator.

 

Al

[Guest lotusPaul]

It looks like you have an open circuit so to speak..The red from the stat will be open and allowing coolant to flow to the expansion tank. .from there the blue to the rad, the pump will there by be ignoring the stat..This will most probably be part of the problem.

I'd look into developing a simpler system. Not only to cure a issue but also less hoses and joints equal less leaks.