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Hi, I replaced my thermostat today in my X reg 156 2.0 Selespeed after a few months of driving around with tepid heating and a temp guage that hardly moved!!!!. Easy job to carry out, about an hour, but what I'd like to know is what is the normal operating temperature with a new thermostat? I took it for it for a test drive and the temp guage fluctuated between 70 and 90 degrees. Is this normal as I've never seen the temp guage move this much before?. Any answers would be greatly appreciated.
 

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It's usually just on or just under 90 on the temp gauge.

My 2.0 166 tends not to fluctuate that much - rises a little whilst stuck in traffic on a hot day, until the fan kicks in etc.
 

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It should sit close to 90 all the time once it has warmed up.
Even at speed in sub zero temperatures.
 

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mmm. Could be pointing to a more serious problem but check these first. If its rising with acceleration quite rapidly i'd say either the new one is stuck and not opening correctly (happened to me before) or the head gasket is on the way out or its not bled fully or the water pump is failing.
I'd go with the stat not opening problem first cos you can go check it. Just check your top hose for heat. Should be nice and hot. Give it a hard squeeze several times with the engine running just to make sure the stat isn't sticking. It backs any water into the back of the stat and may free it if its jammed.
With the air lock. when you filled it up did you leave the bung out of the rad to make sure it was full. Then when running up leave the top off the header tank and have the heat and fan on full inside the car. Should get it all moving nicely round and pump out any air locks. Once car is coming up to full temp put the top on the bottle and go for a drive. i find that it will probably drop when you check it the next day. top up and keep an eye on it.
finally failing this there is always water pump impellor failure which is quite unlikely or the dreaded headgasket. Hope that helps
 

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if stat is not opening engine temp would keep rising then overheat ,his problem is running too cool that might just be faulty sender!:rolleyes:
i would do this from cold,baring in mind a new stat rarely faulty
warm engine up from cold and top hose should still be cold ,and when engine gets warm enough the top hose will start to warm up,varifing stat opening temp ,then just look at gauge and this should show around 90 on gauge,report back with your findings:cool:
 

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I had the same problem till I replaced my header tank cap.
 
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Thanks for the advice. After checking the header tank this morning I noticed it was slighty down on fluid, I bled the radiator as I topped the tank up and ran the car with heating on full hot. The top hose got hot as it should and the temp guage rose to about 95 degs when the fan kicked in. Went for a long drive and the temp gauge indicated 85-90 degs all the time, I could see the thermostat operating correctly as the gauge rose and fell. I got stuck in traffic when it went up to 95 and the fan kicked in again. I think its working as it should.
 
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