I have a 2007 4.6L mustang that has been overheating. When the temp outside gets up over 100+ degrees and I am driving the city streets the AC stops blowing cold. When seating at the stop lights the cars idle drops from normal down to 200-300 RPM almost dies then bounces back up. With the stop and go the car begins to overheat.

There are no overheating problems. If I turn the AC off driving the surface streets the temp gage stay in the middle happy as could be. If the temp is below the 90’s outside the AC works on surface streets no overheating. If I am able to hold 45 MPH or just cursing along on the freeway. The AC will kick in and blow cold with no overheating problems. I have driven Tucson to Phoenix like that a few times.

The dealer has so far tested the AC system and came back clear. They have replaced the fan and fan relays which were covered under warranty, but now they are saying that the radiator has blockage which isn’t covered by the warranty and want 700 to replace the radiator and thermostat.

I took the car back after that to do the work myself, not going to pay them 700 to replace 200-300 bucks in parts that aren't that bad to replace. But I wanted to post here to get some input on if there are any other things that could be the problem before I go swapping parts to find that doesn’t fix the problem.

 

As far as the idle dropping, clean the TB and replace the fuel filter for starters.

Do you ALWAYS curse down the freeway?...

 

Everytime I have to deal with Tucson construction traffic.


The idle going up and down also only happens when the AC is on. if the AC is turned off the car runs fine.