Hello Guys, Had this problem for a while now and I want to know if anyone has had this happen to them, and what could the fix possibly be. Every day or so, the temp gauge will go to zero. Engine hot, thermostat changed about 6 months ago. Problem actually started happening before it was changed. Drive half a day, or sometimes 10 minutes, or sometimes as long as 2 days, the gauge still reads zero. I wouldn't worry about it a lot, cause I know its not running cold or hot, but when this happens, the ac compressor will not come on because the computer thinks the engine is still cold.....any thoughts?
BTW, sorry for the long post.

Andy
Cajun Country

 

thermostat needs replacing (again)

Use the search function to find the how-to-do procedure for the replacement.

 

possibly temp sensor????

 

Thermostat...

 

to the forum Andy!

Does sound like your thermostat has failed on you again for some reason.

 

Nope....not thermostat, replaced it again today...drove about 10 miles, you guessed it, temp gauge went to zero. Had more calls to make, about 3:00 this afternoon, gauge starts working again. BTW, temp sensor was changed about a month ago. I work for Coca-Cola, and this is my sales car. I will sometimes put 3000 miles a month. And....Thanks for the welcome.

just rolled over 134500 miles. This is the only problem I've had with this car....I love it.

 

Swing by an auto parts store to have them pull the codes if there are any stored(the major chains do it for free), might be something else going on with it.

 

If you get code - P0128 (Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature) generally that means the thermostat is jammed open.

When you replaced the thermostat the first time, was the inner gasket around the movable valve broken and deteriorated? How about with the latest one that was removed?

Any chance there is still air in the system? There are a couple great descriptions on how to remove all air and get the system working properly in this thread: https://www.chevyhhr.net/forums/how-tutorial-library-21/how-save-%24350-00-thermostat-replacement-2-4l-p0128-24493/

If it is NOT intermittant, do a double check on the connectors at the temperature sensors.

 

I had the problem with the temp digital readout saying "---" and no ac when it happened. Computer readout was P0128. I replaced the temp sender unit and didn't help. So I followed the forum's advice and changed the thermostat. That did it.
It appears that the computer monitors closely to see if the engine temp runs within a certain range. My problem was that it would go too low when it should have been warmed up. It was running around the mid 180's when the ac would go out and temp reading dropped to zero.
I inspected the old thermostat and it had parts of a center rubber gasket missing also the outer seal was loose (I could have done that when removing it). Replacement is a snap with an extension on a 10 mm ratchet wrench. Just remove the 2 bolts holding it in place. A person who has only changed oil should be able to do it. No need to remove hoses.
Good luck!