aMartinez2552

So my truck basically overheats when i'm at a red light, but when i'm cruising above 50 mph it is running with operating temperature. The truck has a new radiator, new water pump, and a new thermostat. I've checked the lines going to the heater core, both sides are hot. I assumed that there was probably air in the system because of all he switching of parts, so raised the front end, turned on the heater, and ran it above 1500 rpm, and occasionally popped the cap off the reservoir. The truck has 120,XXX on it and just recently had the heads changed. If i may also mention, the truck began having this issue after the heads had been changed. Anyone have any ideas on what I can check next?

Good old Bill

I have no experience with the 4.6 engine so here goes. Why were the heads pulled in the first place?

Typically, overheating slow traffic or city driving, the fan clutch is not functioning properly. I am not liking your wording "holds temperature at 50 MPH and this never happened before heads were pulled".

In this case, there is the possibility that the head gasket or gaskets were installed incorrectly.

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