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03 Forester Over heating

We just had a truck load of work done on our Forester. It has about 98k on it We had the head gaskets replaced (Warranty work), timing belt, tensioner, thermostats, crank and cam shaft seal, and water pump replaced earlier this month. On a drive on the highway the car began to overheat…the gage needle nearly went up to the red zone. At the time the AC stopped and hot air was blowing into the cabin. We took it to a nearby dealer who could not detect any problem or replicate the overheating. We drove away and the car overheated again on the highway. We drove it back to the dealer. They had it for two days. road tested it and the thing would not overheat for them. Any thoughts

Overheating at high speed usually indicates a coolant or air flow problem, often from a clogged radiator. A bit soon to be having this problem in an '03, but since the headgaskets needed to be replaced, perhaps a more thorough flush of the cooling system is needed. Or maybe the thermostat they installed is defective. Also, make sure the a/c condensor in front of the radiator is free of bugs and other debris.

Did they run the car at highway speeds?

Another thought: If this problem only occurred after the work on the engine was done, perhaps the timing belt was installed improperly, and the timing is off.

EDIT: Yet another thought: Has the accuracy of the temperature gauge been verified? The coolant temperature sensor or the gauge itself may be off. Is coolant being blown out of the radiator or is it just the gauge indicating overheating?

Gage is reading hot…AC stops when the Gage reads as hot and blows hot air. It has has been driven at highway speeds. The dealer plugged in the computer when checking it the first time which detected that there was not anything that was wrong. They also road tested it and could not get it to overheat.

Well, I’m out of ideas. Anyone else have anything?

You might have the vapors escaping from the open radiator checked for the presence of unburnt hydrocarbons. It is possible that the head gasket replacement(s) were not successful in stopping the compression leak. It is also possible that a head is cracked and that was missed in the orignal repair.

If you can get an infrared thermometer, read the upper radiator tank temperature and the lower tank temperature. Post those readings back as they will help in the diagnosis.

Hope that helps.