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Q: Overheating

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Started happening a few months ago. The van suddenly overheated. We changed the thermostat thinking it was the problem. Still overheated. The head gasket has been replaced on this van already, but it was a while ago. Not positive of the total miles on the van right now, but I'm guessing it's pushing 180,000. The gasket was probably done at least 50,000 ago. Took it to the garage multiple times, they can't figure out whats going on. Doesn't seem to be loosing coolant. They've bled it multiple times, and it was ok again for about 1.5 - 2 weeks at a time a couple times, then we had them flush the system on advice from other people, and it seemed to do the trick and was not overheating for a couple of months, but the heater was not working great, mostly blowing lukewarm air. We decided we could live with it as long as the van was no longer over heating. Unfortunately, it overheated again tonight! Will be taking it to the garage again tomorrow, but not too optimistic. Advice?
My car has an automatic transmission.

The heater not working in some cases may be related to the overheating problem you are also having. This may be due to a faulty heater blower motor or potentially a bad heater core. As you may know, the heater core is a small radiator like unit that circulates the hot coolant from the engine through the heater core which then uses this warm coolant to heat the inside of the car with the help of the blower motor that blows the warm air through the vents inside the car. When the cooling system is not properly circulating coolant through the motor, this results in the warm coolant not being pumped through the heater core properly in order to warm the inside of the vehicle.

Engine overheating can be caused by a number of things such as low coolant levels, a faulty thermostat, or a failing coolant fan switch. As you may know the coolant fan switch helps to maintain the proper coolant temperature by turning on and off at specific temperature thresholds. When this switch is not working properly, this can cause the fans to come on intermittently, all the time or sometimes not at all. When this happens you will notice a temperature spike and drop occasionally as the fan comes on and off. When your thermostat is not working properly or is stuck closed, this will not allow the coolant to properly circulate through the engine, which may cause the engine temperature to fluctuate erratically or in some cases just remain hot. As mentioned above, this also restricts the warm coolant from flowing through the heater core which uses this to blow warm air into the cab of the vehicle. I would suggest having an expert from Your Mechanic come to your home to diagnose your cooling system.

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