WHen you say the heat comes and goes and it runs hot, the first thing that pops into my mind is a bad headgasket. However, have you ever replaced the thermostat? Also, have you ever tried flushing the cooling system to see if that helps?
Before I jump into a head gasket, I would try flushing the system and replacing the thermostat. If that doesn't help, then I would check engine compression to see if there is a low cylender. You may want to do that before anything to possibly save the money on the other things.
Here are the directions for checking compression.
Let me know what you find or if you have other questions. Also, if the car only overheats at a stop and not at highway speeds, let me know that before you do anything.
https://www.2carpros.com/dia/how_to_check_compression.htm
Joe
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Monday, March 8th, 2010 AT 4:26 PM