Still OverCooling

[redmaestro]

Just to keep you all updated..... I changed the thermostat on the Efi this morning whilst the weather was nice. The existing gasket came off cleanly, so I reused it with some liquid gasket stuff just in case.

Anyway, i've just been for a 8mile run on a 60mph road and she is still overcooling :-(. The engine was fairly warm when I set off because I had run the engine to check for leaks etc. The hoses and thermo housing are bone dry so I know it's sealed properly but am baffled why she only get to 1/4 on the temp gauge. Is there anything else I can try?

[secubis3]

I have a similar problem not to long ago. I drover for about six months without going above 1/4. In the end my thermostat housing, gasket and head gasket went.
My garage said the thermostat stuck half open (that was a new one).
He fitted a new one after testing it in a pan of hot water.
He fixed all the damage, but told me that when changing something on the cooling systen it is best to drain and flush all the old rubbish out as the seddiment and rust will only get to work on the new stuff.

You may also have some blocked water channels, so the only thing I can suggest is, if you have not already done so is drain and flush the whole system and wash out all the pipes, radiator and heating matrix.

[redmaestro]

.........You may also have some blocked water channels, so the only thing I can suggest is, if you have not already done so is drain and flush the whole system and wash out all the pipes, radiator and heating matrix.

Thanks for the reply, I did that earlier. Once the blue antifreeze had flushed out, the water ran clear.

[secubis3]

I might be asking the wrong question here, but is the thermostat you had/have in the correct type?
I know some open at a lower/higher temp.
my old one had different marking numbers to the one the garage took out, he replaced like for like.

I know you tested the engine with a run but have you done a compression test to make sure to eliminate a blown gasket. Mine ran for a good while with a blown gasket between 2 & 3.Better to check just in case.

[norbert eggcup]

deffo sounds like wrong temp thermostat or it may be dud- just cos its new dont mean its ok!

[G Force]

Hi Redmaestro.

It is just possible that you have two problems i.e. Poor heater performance linked to a heat exchange issue or heater box flap position. Check also for restrictions in the rubber heater hoses that connect to the metal pipes at the bulkhead.

Also there could be an electrical problem causing the temp guage to read low, like poor connections between coolant sensor and ECU or faulty sensor or ECU.

It would be a good idea to test the resistance value of the coolant sensor with a multi meter to see if it is reading between 150 ohms to 250 ohms, when the engine has run at 2000rpm until the radiator cooling fan comes on with the car stood still.

[Rich]

You could also try replacing the rad cap, or at least swopping it for another for a while, to see if it makes a difference. I had a overcooling problem once, and changed everything but the HG, replaced the expansion tank and cap, and suddenly, it was ok?

[Simon]

For a while my temp gauge ran 1/4 for a long time. I reconditioned my heater at the weekend and adjusted the linkages properly. All of a sudden the gauge is reading "normal" for my car, in other words about 2 marks off of half way. I now have a hot heater too. Has your matrix been replaced at all? What is the state of the foam insulation around it?

[redmaestro]

Thanks for all the replies, I'll try and answer to all of the suggestions:

* HG was replaced about 6months ago when she had an oil leak. Since then, oil leak has stopped, no 'mayo' in oil pipes and water level has never dropped not has is any traces of oil in it. She was overcooling long before the HG was replaced.

ECU - I have a spare one in the garage somewhere, so I can check with that.

Temp Sensor - Thanks for the tip GForce, I'll try that sometime this week. The rubber hoses are not restricted.

Duff Thermostat - The one I took out was a halfords one and the new one was the QH one. Both had the 88 degrees stamp. They both show as 1/4 on the temp gauge

Recon Heater - Simon, how did you recondition the heater? I've readjusted the linkages and the blower is giving out as much heat as it can - which isnt much. As far as I can see, the foam seems ok

Rad Cap - I'll give that one a try, must admit I didn't think of changing the cap.

Thanks again for all your suggestions, I'll keep you all posted with what I find

Redm

[E_T_V]

If the wrong temp sensor is fitted then although the sensor looks the same then it reads low. I think the sensor bodies are different colours to distinguish them from each other. I think some other people have had this issue with the wrong sensor fitted. To check run the car until the fan comes on and note the temp on the gauge. It should be above half and often about 3/4s the way up the gauge. If it is below half then you've got the wrong sensor or an electrical problem somewhere with the sensor.