Hello, posting for a friend. She has an 02 Montero. She has an odd problem that has myself, another friend, and the mechanic stumped. The problem is when she drives slow, or sometimes idle, it overheats. First, local shop replaced the thermostat, then another mechanic found a miss in #3 cylinder and found coolant in the cylinder. He put block sealant in it and that took care of that problem. I don't believe any got back into the coolant and onto the thermostat, because if it did then it would overheat all the time, my thinking anyways. Other day my buddy and her were at WalMart parking lot, after trying to diagnose it, the engine fan was running and dash temp gauge was "normal". As soon as the condenser fan kicked in it started to overheat. And she does lose coolant, boiling over, so the dash gauge isn't malfunctioning. I read on fixya.com one reply said it could be condenser restriction??? How and why would that affect engine temperature?

 

Ok, just realized the flow restriction. I was thinking coolant flow...not air flow. Also the radiator is new.