« Reply #2 on: December 14, 2011, 08:35:17 pm »
plus one for Greg.
I would suggest possibly its the water pump if its not just low on coolant or a tstat.
If the engine is spinning at cruise rpm(3000 or so) and its fine, then at idle(800 or so) the water pump is possibly not keeping up? If the impeller fins are worn or pitting etc, or even loose on the shaft, it won't move much water at low rpm but might be able to get some moving at higher rpm.
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