cowboyjlove

I have a New Mexico 2007 Lt HHR with 142k org miles but have been having the same problem off and on for years. Of corse if it cool/ raining out side it won’t over heat but in the summer late in day the car wants to get upto 217 and that worry’s me. If I turn on heater it will drop back down to 194 the thermostat temp but if I drive 75 or higher It wants to climb up again if I drive slower It’s generally fine but not always . I replaced the thermostat years ago from a 180 to 194 and that didn’t fixed it. At idle it will get up to 201 and go back to 194 with air on. It doesn’t appear to be leaking anywhere . The fan turns on with ac . Fluid levels look fine it’s hard to tell the reserve tank but it has about 1/4 to 1/2 of orange looking dex cool in it. I never have to add any coolant to system . What I can tell radiator doesn’t look clogged or have tons of bugs in it. I turned it on for a little while without cap and saw no bubbles but not sure how long you have to wait to burb the system.

guppy

The fan turns on at 217° and cools it down. If the A/C is turned on then the radiator fan should run all the time. If you are driving down the hiway at 60 mph and it climbs to 217°, I would say something is not right. I dont think it would get over 200° running 60 mph on flat hiway on a 90° day. Driving over 70mph, my engine runs a few degrees warmer (200-205°). Now the thermostat!!! Make sure it is the correct AC Delco thermostat, like everyone is going to tell you , it does make a difference. If you are sitting at a redlight with the A/ C off, then the temp will rise to 217° before the fan kicks on which should bring it back down to about 195°. Are you only going over 205° when driving in excess of 60mph?

guppy

I think this might be normal. But understand that 225-235° you are getting in the danger zone of cracking a head. So watch that temp close when speeding. Use the DIC to watch temp, not the useless analog gauge.

donbrew

Why the heck would you think putting a 195F t-stat would LOWER the temp? That would set the MINIMUM temp to 195F and the fan would stay on forever since it turns on at 217F and back off at 180F

Overheating is caused by a problem with the radiator or a coolant flow problem. The job of the t-stat is to keep the temp ABOVE it's rated temp.

Oldblue

How old is the Dexcool, let’s not forget it has a 5 year life, it breaks down after that , if heated up like your saying , old Dexcool will start to crystallize