2006 Chevy Aveo Overheating

[thesharpinator]

My friends 2006 Aveo started overheating about 2 months ago. Started out just a little so I wasn't worried about it. However it started getting worse. Now it climbs to about 3/4 on the gauge and the A/C gets warm. If the A/C is left on it continues to climb. If you turn the heater on though, it rests about 3/4. A year ago I replaced the thermostat because the OEM plastic housing was cracked, so I didn't think that was it. I have since replaced the water pump. I pulled the radiator and cleaned it out, it is perfectly clean inside. Coolant is clean, and full. Also performed a hydrocarbons block test to check for a bad head gasket, twice actually, and it passed both times. It's got me beat, I have no clue what it could be. Any ideas?

[thankful_ragamuffin]

I suspect the cooling fan is either not kicking in, or only running at low speed (2 speed cooling fan if memory serves). The warm A/C tells me there is probably insufficient airflow over the condenser (and rad) either due to the fan or air blockage. You cleaned the fins on the rad and condenser when you cleaned the rad out, right?

[thesharpinator]

Yes I washed it off with a pressure washer. Radiator actually looked really good. I also checked the condenser for any blockage, cause that was my first thought that something got trapped. The fan works, it kicks in at the right time, and comes on with the A/C as it should. Also it doesn't heat up as much at an idle, but gets really hot going down the road.

[thankful_ragamuffin]

Do you have access to a scan tool that will read actual temp versus what the gauge is showing or even a laser thermometer? It seems you have done your due diligence in checking all the normal possibilities. Overheat at highway speeds with the high airflow over the rad is rare. You didn't mention if you checked or replaced the rad cap.

[thesharpinator]

Yes I have an Infrared Thermometer. It reads about 230 at the back of the thermostat housing, so its definitely hot. And no I have not replaced the cap on the jug, as it is just a screw on cap. Started without the cap on earlier, and it started boiling out at just above half, which I found odd. But the cap was off so the system wasn't under pressure.

[avguy]

Sounds like it's either a broken water pump impeller, or more likely the thermostat. Yep, I see you replace it last year, but $hit happens.

[thesharpinator]

Yea I'm gonna pull the stat later and run it without it and see what it does, gonna flush it too, maybe something got stuck in a water jacket or something. But I replaced the water pump hoping it was the impeller but that wasn't it.

[petrified.rabbit]

i once put a thermostat in a maintenance, and the car overheated the first time i started it. put in another thermostat, problem went away..


not saying that is your issue, your description suggests the fans, but since you say they are working properly i would do the thermostat again I guess. But a bad thermostat would keep the rad cool, meaning your AC would not get hot.

now when you say you did a hydrocarbon block test, what did you test? a sniffer looking for escaped exhaust around the head? or the dye test of the coolant? If the head gasket is compromised, it does not always leak out of the side go the block. But If the coolant heated up and boiled with the cap off, how long did it take? I have let 4 cylinders idle a long time without them boiling over (10-20minutes) so if it boiled over quickly, you might want to do a cylinder leak down test to see if the head gasket is blown to the oil or, more likely in this case, water jacket.

[Scanman]

i once put a thermostat in a maintenance, and the car overheated the first time i started it. put in another thermostat, problem went away..


not saying that is your issue, your description suggests the fans, but since you say they are working properly i would do the thermostat again I guess. But a bad thermostat would keep the rad cool, meaning your AC would not get hot.

now when you say you did a hydrocarbon block test, what did you test? a sniffer looking for escaped exhaust around the head? or the dye test of the coolant? If the head gasket is compromised, it does not always leak out of the side go the block. But If the coolant heated up and boiled with the cap off, how long did it take? I have let 4 cylinders idle a long time without them boiling over (10-20minutes) so if it boiled over quickly, you might want to do a cylinder leak down test to see if the head gasket is blown to the oil or, more likely in this case, water jacket.

If this is the case you should be able to check the oil. If there is grey matter in there, a classic sign of oil & water mixing, then what rabbit says is conformed.

[thesharpinator]

Well pulled the stat over the weekend and put it in a can of water and heated with a torch. Got it way above boiling and it never opened. Stuck a new one in it and runs at perfect temp. $5 and 15 minutes after spending hours. Oh well, never rule out a new part folks! Thanks for your help!