New thermostat, runs cooler!!?? - Alfa Romeo Forum
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(Post Link) post #1 of 8 Old 10-11-08 Thread Starter
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New thermostat, runs cooler!!??


I've just replaced the thermoatat on my 3.0 GTV due to it running cool (60 degrees) on the motorway despite running at around 90 degrees during normal driving, around town etc.

Replaced the thermostat on the weekend (from an Alfa main dealer). Around town the car runs at around 70 degrees! This seems illogical to me as I replaced it assuming the old one was stuck open and it ran at 90 around town before the change!

I have not run it on the motorway with the new one yet. So far I'm confused. Any help is appreciated.
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Re: New thermostat, runs cooler!!??

I have change my termostat too. Aprox 70-75 on highway and 90-95 in town.
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Re: New thermostat, runs cooler!!??

This is an ongoing "problem" which I find difficult to agree with a lot of people on. My car will run at approx 80-90C around town and will never go above 92C in heavy traffic. On motorways, and with faster speeds in general, the temp gauge will drop to around 70C. This is the same story as many, many others have.

Now here's my results: upon starting the car from cold, I have held the coolant pipe that runs from the thermostat, it would stay completely cold for approx 8-10 mins, at which point the engine would have got to 80+C and a sudden rush of heat would make it's way down the pipe. Therefore I would deduce from this that the stat is fully closed when cold and opening properly. NO warmth is felt from the pipe at all during the first 8-10 minutes of the engine running. Which wouldn't be the case if the stat was slightly stuck open. I even tested the stat in a pan of boiling water and saw that it opened and closed - albeit quite slowly - with no problems. My fuel economy is as Alfa Romeo state in the GTV brochure and performance is fine.

I would be inclined to think the temp sensor is the culprit in a lot of cases, not the thermostat. Unless of course the stat is not adapting to the temp change quickly enough, which would make sense.

With reliability will ultimately come monotony.....

Last edited by StormVR6; 10-11-08 at 20:45.
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Re: New thermostat, runs cooler!!??

Changed my thermostat at the weekend on my 2ltr TS. It had been running at 50-60 on the motorway and only up to 90 when stationary.

Now runs 60-70 on the motorway and 90 in town!
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Re: New thermostat, runs cooler!!??

Changed the thermostat on the 2.0 after that, it sat around the 90 mark.

The 3.0 varies between 85 - 95 slow driving or in town but can drop to about 70 on a long run. Was a bit worried at first but seems ok, doesn't overheat and the heater works fine.
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Re: New thermostat, runs cooler!!??

i think the temperature varies from country to country, in my case the norm is 90.. it's very hot here.. also check on the 50 amp relay for the fans.. it could be a cause for bad temp
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Re: New thermostat, runs cooler!!??

Changed the thermostat and temp sender on my 2.0JTS yesterday. Before it ran at just over 60 on motorways in the summer and below 60 now it's getting colder. I don't think my fan had ever switched on. It now runs close to 90 wherever I drive and the fan kicks in just over 90. Hopefully the mpg will go up a bit!!
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Re: New thermostat, runs cooler!!??

I had my thermostat changes recently as the old one was stuck open. I thought it still might be running cold so this weekend I did a bit of an experiment with a temperature probe and a multimater. I measured the temperature of the coolant in the header tank, started the engine and watched the temperature rise. The hoses from the thermostat to the radiator stayed cold (not like before with the stuck open 'stat). And then warmed up as the thermostat opened. So at least the new thermostat is working. The interesting thing I found was that the temperature gauge needle in the car moved to 50 degrees when the actual coolant temperature was measured at nearer 60 degrees. My thermostat opened up at a measured temp of 84 degrees (should be 87 but allowing for tolrances etc, near enough). At this measured temperature, the temperature gauge in the car read between the second (unnumbered) tick and the 90 degree tick. I thought this was more likely to be 75-80 degrees, hence my experiment to check. It seems that the temperature gauges aren't very accurate or linear. Mine stays between the second tick and 90 degrees, which I now know is 84 + degrees during normal running then gets up to 90 degrees when stopped in traffic. All good!
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