Plymouth Aclaim initial overheat

Here is one for you guys! My 1995 3.0 ltr Acclaim initially overheats
when first operated on cold mornings, usually within the first 5
miles. When it does, I stop, turn it off, then restart and (airlock ?)
seems to go through and then it's good for rest of day. Fan motor
changed as well its sensor, radiator changed in the last 2 years,
radiator cap changed, thermostat changed as well. It isn't losing any
coolant, runs great besides that. On warmer mornings, I does not
overheat. I was told only other possibility is leaky head gasket but
see no leaking coolant anywhere. An airlock seems to form in the system
on cold mornings but once it goes through, there is no more problems. I
have had 3 mechanics look at it and no one seems to understand this.
You guys should be able to help me, I hope. This car has 419,000 kms
and has been very faithful.Any ideas?

 

The only thermostat that will work correctly in this engine is
the OEM one, if you used one from a dime store, that would be the
first place to look.

Just because you don't see any external coolant leakage doesn't
mean the head gasket isn't leaking.
The only 100% certain way to rule out a leaking head gasket is to
pressurize each cylinder with compressed air with the cylinder at
top dead center and look for air or any sign of coolant movement
at the radiator filler neck.
Since the rear head gasket is usually the first to fail, I'd
start checking at the rear cylinder head.