2008 HHR LT 2.0L

drivng home last night an A/C stops blowing cold. I notice analog coolant temp gauge is pointing all the way to the cold side. No check engine light. I pull up digital coolant temp and it shows - - - F. So the next morning I remove the thermostat and drop it into a pot of boiling water. It opens and closes as expected. I inspect for the rubber hanging out the side and it looks perfectly normal, no black rubber hanging out. I remove the temp sensor and test for ohms, it is 2k ohms cold and 185 ohms in boiling water. I have a spare sensor so I tested it an it reads 2.3K and 190 ohms. I put it all back together with the spare sensor. I took 2.5 L of coolant to refill, not sure if that is more than normal. I should have checked coolant level before starting. I pull codes ( P0128 & P0573 ) and clear them. I take it for a 1 mile test drive. Temp hit 180 in about 2 minutes, it never hit 195 and it is 85 degrees outside. I am about to drive to work, so I will let ya know if a/c goes hot again. Any ideas?

 

I’m thinking time for a new AC Delco 131-158 180 degree thermostat and drain and refill with fresh 50/50 Dexcool and potable water. It should be changed every 5 years.

 

I drove on the hiway for about 20 minutes to work. Ambient temp today in Dallas is 95 degrees. Coolant temp never topped 196 on my drive until I get to the parking lot, then it started to rise to 210 almost immediately with A/C on. I pull into a parking spot at 1:46 and it was idleing at 212 degrees. I sit for a few more minutes and at 1:49 it had climbed to 216 degrees with A/C on. I popped the hood and checked that the fan was running, it was. There is no coolant leak. This is hotter than I am comfortable with. Perhaps the new coolant sensor is off a little or I just need to burp the system. My driveway is at a nice incline so it will self burp tonight as long as I keep the overflow bottle half full. I am a little confused about the P0146 and the thermostat looks and tested perfect. I hate to drop $60 for a thermostat, but if I loose A/C again I'll give it a try. And yes, the ACDelco is $59 on rockauto!!

 

I replaced both upper radiator hoses, rad cap, plastic tee and flushed all coolant a couple months ago.

 

Good, then when you burp it you still look under the rad cap, don’t depend on the coolant recovery tank.

 

2.5L is a lot to lose from replacing a t-stat. What P0146?
P0128 could be from a bad temo sensor. It means that the temp did not reach 180F as fast as the computer expects.

 

I think the car was low on coolant.. Burp it a couple times and be sure the level in the coolant recover tank is correct.