PhoenixKnght86

I drive a 2002 Merc Sable Sedan with a DOHO Duratec 30 v6 engine with 114K miles. She recently (as of three days ago) had a new thermostat put in, believe it would solve the current problem I am having with this car:

She overheats in slow moving city traffic and it may or may not be affect by the AC. I have seen it happen with the AC and without. The mechanic says both fans do work, I checked all her fluids before the trip and even after. Today it happened in Ithaca, with the AC off but with the minor climate controls on (and had been this way for 4 hours previously). After turning off the climate controls, she began to lower her temperature and as we moved further into more free flowing and faster traffic, she eventually returned to normal.

This has happened more than once and only in this type of setting, with the heavy and slow moving traffic. It has been hot days in all three cases but I don't understand how the stop and go traffic could be heating the car up.

Our mechanic found no other problems that could be causing this and there are no recalls on anything related. Has anyone had similar situations with their cars or have we overlooked something?

jwko

When you drive the wind pushes through the radiator helping to keep it cool. When you are in stop and go traffic, not much wind is allowed to pass through, therefore the fans are needed to help out. Are you positive the fans are coming on?? If so, I would check for any obstructions in front of the radiator/condenser. If that's clear, I'm betting you have a internally clogged radiator or possibly even a bad water pump.

suednim

My guess is that the fans are not working when they should. If the W/P or rad. was the fault, then the increased speed making the temp. go down would not be happening.

jwko

Sure it would. Increased RPM would help push coolant through a "partially" clogged faster. Or a bad water pump impeller may not produce enough force to push coolant through a radiator at lower RPM.