Thermostat stuck open temp

[rzr6-4]

This is for a 93 Sierra 1500, I didn't feel like joining another forum so just figured I would give it a shot here.

Front end accident a couple years ago, slowly been rebuilding and its mostly street legal now. What I'm seeing now that I'm starting to drive it around some is that the coolant will get close to operating temp and then suddenly drop down to the first line like its barely warm and stay there. Last weekend I had already driven a couple miles before doing a 90mph full throttle pull and it would not come back up above that first line. I'm wondering if when the thermostat opens if its getting stuck and staying fully open until the engine cools all the way down before starting to close again. Obviously the thermostat being open will cause it to run cool but I didn't know it would run THAT cool though, or do you think its something else.

From the engine block forward everything is new. I don't think there's air in the rad but I will check again this weekend. I can pull the thermostat and put it in some boiling water but if it does in fact open, then close when cooled off I don't know if that is going to tell me about getting stuck in that middle ground.

 

[Wallyb4]

Are you getting heat from the vents, when the temp drops to the first line? If so you could have either air in the system stuck at the high point of the system or a bad sensor.

 

[rzr6-4]

Are you getting heat from the vents, when the temp drops to the first line? If so you could have either air in the system stuck at the high point of the system or a bad sensor.

Unfortunately the AC is the only thing I don't have hooked up yet so to make sure it doesn't get turned on when its not ready I just pulled the fuse for the whole thing.

 

[NCRaineman]

Unfortunately the AC is the only thing I don't have hooked up yet so to make sure it doesn't get turned on when its not ready I just pulled the fuse for the whole thing.

Let it idle for a while with the rad cap off. That should get any remaining air out of the system. Also feel free to pull the thermostat and drive without it. If you are in the southern part of the country you don't really need it. That should tell you if it is a thermostat problem or something else.

 

[rzr6-4]

Finally got it legal(ish) and got it going around on the roads. I put the fuse for the heater back in and the air is coming out plenty warm. With how warm the air coming out is I wonder if the temp gauge is misreading.

Overflow tank was empty but radiator appeared full. Filled overflow to the correct level before driving 40ish miles. Temp gauge will come up just above the first line but still no where near normal operating temp.

 

[Daw14]

Keep trying to burp the system, sounds like it still has an air pocket or few.