2000 Grand Prix, What is the normal operating coolant temp?

2000 Grand Prix Gt
90,400 miles

I have a heating issue that I’ve been trying to fix for over a week. I had the coolant system flushed and shortly after the service engine soon light came on. I went to the local Autozone to use their code reader resulting in code P0126. This code points out either low coolant level, a bad thermostat sensor, or a bad thermostat. The level is good, I changed the thermostat sensor as well as the thermostat. I bleed the system twice but my car is running at 210 degrees and at times the needle will increase and return back to the 210 degree mark. I have no clue the normal operating temperature of the car. The thermostat that I installed opens at 185 degrees. I thank you in advance for any advice.

What is the normal operating temp for the coolant?

Technically with no real cooling system problems your coolant temperature should be around the operating parameters of the thermostat. If you are stock then the best one to use is the OE 195 degree. Better engine warmup time and fuel economy. Mine operates well under the 210 mark on the temp gauge around the main hash mark above the 160 degree point but I'm not stock. A constant 210 degree reading is not quite normal.

What does it do with the A/C on? Also, what brand of coolant was used and was it mixed properly.

I'm using Duralast thermastat 195 degrees, Preston antifreeze OE, and the mixture was put in by the shop who flushed my system. I've purged the system for the third time by using the little brass bolt on top of the thermastat housing again yesterday. The car wasn't doing this until I had the system flushed.

Thanks for the info
Coleman

Yeah the Autozone special. Best thermostat to use is the AC Delco Premium or the Stant Superstat 195 #59849. Maybe the shop did not flush properly and crud like old Dexcool sludge is blocking the radiator lines. You may need to do another flush. I do my cooling system flushes DIY because I don't trust the shops.

Is it running at the 210 with A/C on or off? With A/C on the cooling fans will come on in low speed and the reading should drop.

It's running 210 with the A/C on and slightly above 210 with the A/C off. Normally I do my own small jobs but due to military operations I was unable to and know this is what I have.

Thats abnormal. I'd take it back to the shop, explain the situation to them and have them perform on the warranty if any?

What branch of service? I was Army.

It's running 210 with the A/C on and slightly above 210 with the A/C off. Normally I do my own small jobs but due to military operations I was unable to and know this is what I have.

Dumb curious question from this grunt: What did the shop say when you took the car back with the heating problem induced by them?

I agree with Bob, ditch the thermostat for the AC Delco Premium or the Stant Superstat 195 #59849.

If your car is not mod'd, then put the 195 back in. Eventually, I think the computer will pick up the fact the thermostat is opening too quickly, throw a code and force you to put in the proper stat to make your SES light remain off and make it happy.

This is my first weekend back so, I have not had a chance to talk to them. I made another thermastat change back to the OE one and it seems to be running fine. I let the car run for over 20 minutes and during this time I purged the system also.

Thanks for all the help

Coleman