Have you tried pulling out thermostat
Yes it will take a bit longer to warm up
But you will see if it keeps gauge from moving around during stops and when driving
Not all thermostats are the same
High flow ac delco on top
original type replacement gm ac delco on bottom
High flow pump push around 20 percent more coolant, like having your truck rev 20 percent faster
i don't dog my truck so having cavitation problems at 8000 rpm
is not an issue ...
The high flow water pump and thermo worked wonders for my truck
I went through same with original water pump and thermostat
Changed it out to higher flow system
Truck is much happier
After installing OEM parts and same results/ problems where it would creep at stop lights
Actually, once...
I run a high flow water pump
Flowkooler with a high flow thermostat
With stock temp
Truck used to come to stop light and do what your truck did
But never over heated
Now it runs and needle never moves once it warmes up
Even on the hottest days it’s same temp as coldest
Glad I used the high...
50 PSI sounds low
before you start chasing ghosts
spray some starter fluid into intake throttle body
Not too much and see if she fires up
I use Delphi pressure regulators
also if you are back there replacing regulator
replaced the Oil Pressure switch (it also controls fuel pump )
Heat that nut up , penetrating oil then heat it again and put your wrench to it
when it stops turning, remove wrench and heat up again and turn some more
as it cools the aluminum nut will shrink
to prevent galling in the future , I use it on o-rings and threads and mating surface
just a drop on mating surface and a couple on threads,
Nylog blue gasket and thread sealant
made for refrigeration work
every thing will assemble sooooo smoothly and more important, come apart in the future...
And while cap is off you can watch rotor turn while cranking
With key off you can turn rotor maybe 1/4 inch
Someone correct me if I am wrong
It should look like it’s riding up the gear a bit
Hard to explain but you have to do a couple of good ones to feel a bad one with worn gear.
Check your distributor pickup coil for Hall effect in Ac mode with multimeter for proper voltage while cranking
You get fuel pressure for a short time (normal) them no pressure cause computer does not see pulses from distributor
Hence no spark
Easy to check before throwing parts at it.
Check...
Unfortunately with the swap everything is possible
Always start diagnostics with the basics
Power and grounds
Then you can move forward with confidence
Compressors have stupid grounds locations that don’t like to be messed with as the harness ages.
Diode is suspect weak point
If you tug on...
you could check to make sure your AC relay is getting power
Then measure voltage at compressor
If you see 12 volts on one leg
Then you have a ground issue
With Ac system on .
before tearing back into it
Get some gauges to see where you are as far as pressure
I don’t think it leaked per your...
What color is your compressor ?
I believe this is true from what I have seen
AC Delco “black” ones are rebuilt units
Natural aluminum units from ac delco are new.