97 F-150 4.6l V8 225k. Need Help! Here is my trucks history. On a cold engine overheats after driving less than 10 miles. have excessive pressure in system. T-stat seems to be opening late. I have replaced t-stat, more than once, water pump, radiator, hoses, fan clutch, pressure cap, temp sending unit, cyclinder head temp sensor, and serp belt is within operating range. I also performed a compression check. #7 and #8 were a little weak. I then did a leak down test on all eight cylinders and found no leaks. What could possibly be making my truck overheat?

 

i believe you have a small hole in one of the head gaskets. you have a small amount of cyliner pressure entering your coolant system. i have had this before on a couple vehicles. Go to Auto Zone and get a bottle of "head gasket repair" of similar. It cost about $10. You will need to drain the cooling system and flush with water 2-3 times. no antifreeze left. Then refill with clean water and the gasket repair. Pour the gasket repair into a gallon of water, mix up good, then add it first, then top off with clear water. Start the motor and let it idle for a few minutes. Drive down the road at 30-40 MPH to warm it up a little and let the thermostat open. You dont want a lot of RMP, keep it in the 1500 rpm range, no revving. Run around for 20 minutes and see if you still have the overheating problem. If you wont freeze, let it set a few hours or overnight and run another 30 minutes. Then drain and flush. Leave the radiator open for 24 hours to get thesealer good and hard. Refill with antifreeze.

 

read this

Bar's Leaks Head Gasket Repair

 

So did you repair you gasket with this or at a shop? Or did you find another solutioin to your problem.