to long to idle down when first started then engine stalls + overheats. on 1992 GMC 1500 Pickup

a water leak prompted replacement of the intake gaskets which caused a crack in the manifold. repair was done and again replaced on engine. I visually watched a Diagnostic done and no problems were shown. since then problems like over heating after 2 new thermostats. Shut down and wait 15 min or so and temp drops to 180. I know it is over heating when the overflow tank fills so heat gauge is functioning. This AM (about 1 week after the manifold work) I start engine and same thing with the temp but this time engine does not want to idle down in the normal time of running and when it does (around 45C)it stalls dead. TPS is new, most vacuum hoses replaced, EGR valve replaced at the same time as the manifold work, but should I be able to turn the valve while it is attached to the manifold? After 19 years of service one can expect "some problems" but this is going in very odd directions all at the same time. Can someone help?

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1 answer 2 comments
sounds like a blown head gasket. you need a shop to do a leak down test to verify. if the intake cracked from overheat, the heads may have also cracked.

I believe the intake manifold cracked because it was removed and after 19 years of use it was likely a little stressed. Prior there were no problems other than a small coolant leak between the intake manifold and the block and only after reinstallation did it sound like a tractor caused I am told by a crack near the throttle body possibly (I'm guessing)caused by a torquing problem. Do you have any other suggestions as I am not convinced the heads are the problem but will not discount your suggestion and place "heads" on the list of possibilities.
Thanks Roy
the leak down test will verify the integrity of the motor. then from there i would have radiator flow tested.

as far as the manifold crack, unless it loosened up and twisted, it would not crack from being old.