leaking head gasket
I flushed the coolant system and replaced the thermostat and radiator, idled it and it was fine.... Until I drove it and got up to 60 and it started to spike in temp. Tried the "Cadillac Pills" and nothing. Seems that it's a leaking head gasket that puts combustion gases into the coolant system creating steam and air pockets and over heats it. So my last ditch effort will be to flush the system and add the Blue Devil gasket sealant to try and repair it otherwise it's going to be tearing the head(s) off and replacing the head gasket and head bolts and checking the head surface.
pressure in the system is building so fast
I am now suspecting a Blown head gasket as the water Jacklet builds pressure too rapidly in my opinion. I really dont want to Tear the top of this engine
I figured out that the pressure in the system is building so fast that when the thermostat tries to open it cant overcome the High pressure the Radiator cap is 18 Lb So I bought a 7Lb Radiator cap and the problem seems to be fixed.
the 7Lb Bleeds off the exhaust gasses and keeps pressure from going above 7Lbs per square inch now the thermostat can successfully open
Auto Zone part numbers are 7018 = 18lb I now have 7007 7Lb wow now I can keep the car and drive it and not have to worry about the thermostat sticking
blowing head gaskets
These motors are notorious for blowing head gaskets. The easiest way to check: Take off the cap to the surge tank. Have someone rev the motor while you look into the surge tank. If you see bubbles that are larger than a millimeter, then exhaust gas is getting into the coolant. (Blown head gasket)
White smoke will come out of the tail pipe only the first few minutes as the car warms up. This is because coolant has seeped into the exhaust system and it's burning out as the car warms.
But as the engine is running, no more coolant can get into the exhaust because of the high pressures in the cylinders. This is what makes the exhaust blow back into the coolant system.
The reason your car overheats is because that exhaust gas is creating air bubbles that will collect inside of you heater core and radiator. This stops the coolant from circulating correctly.
Unfortunately, NO ONE wants to rebuild these motors. (Requires a large investment in tools that can't be used on any other motor)
Your only option is to find a used motor or order a crate motor from a dealer. (Astronomical)
If you decide to replace the motor, make sure to have the mechanic look up a T.S.B. (Technical service bulletin) that was issued by the manufacture for your vehicle.
They require a special thermostat. (Why these motors blow their head gaskets)
If you replace the motor without locating this special thermostat, you will only blow that motor also.