Hi, i just had my coolant thermostat replaced and the other day the check engine light came on. i went to autozone and rented their diagnostic tool and it gave me the code that read something like "coolant thermostat-...not running at the right temp." i read up some on it and i believe that the thermostat is stuck open. does this sound right? and if so, how do i go about getting it unstuck? Thanks in advance.

 

If that's the case I would just replace it (again). You may have got a bad one, I wouldn't bother trying to mess with the one that's in the car.

 

My guess P0125 set, it means engine not reaching operation temp fast enough. Thermostats are likely cause. If your new thermostat was at a lower temp rating that stock, it will set code. Make sure cooling system is not low, air pockets can make coolant temp sensor read wrong, another possibility.

 

I didn't think about air posckets from him changing the Tstat. Be carefull they can cause it to run hot also.

 

yes that was the code that it gave me. i will try to find any air bubbles and ask the mechanic if he put in a stock thermostat or not. Thanks

 

...and also, i think the thermostat is stuck open because it takes forever for the heater to warmup (even though it is 20 degrees out). i can drive for 20 minutes on the highway and the heater will still blow cold air

 

That could also be signs of low coolant. Have him pull the thermastat and take a look at it. If it looks fine make sure he takes special care to get all the air out of the system. If it's like the LSx's I work on dayly you have to spend a little time to bleed it all out.

 

I just went through the thermostat issue.

For 2 years the engine lite would come on, but only in winter, in summer it was off.

In winter heater would produce lots of heat, but lite came on around October when it turned cold, the engine lite was checked out for codes at 3 diffrent dealers, all stated the stat needed to be replaced,m but i held off do to ridiculas cost part $60.00 with gaskets, and almost 5 hours labor, total approx $700.00.

This winter I started to get a slight burning smell like old dirty oil, that had me concerned, car was overheating, so I had stat changed at dealer.

CAR DOES NOT RUN ANY DIFFENTLY, AND STILL HAVE A TRACE OF SMELL, BUT LITE IS OFF
2003 CTS WITH 96,000 MILES.

So the safe and expensive bet is to change stat, on what is a very poorly designed cooling system, when compared to a GM V8 the stat is $20.00 and takes 15 minutes to change in driveway.

 

i dont wanna sound like an moron or nothing, but what's a stat ?