paccar excessive coolant pressure

Back feeding the discharge line from where it connects to the dryer is one of the ways. You disconnect the line (biggest one) and use an adapter to hook it up to shop air. When you do that, you'll get pressure in the surge tank. If you have a cooling system pressure tester, you hook that to the fill cap for the tank and let the shop air run for a few minutes. When you open the valve on the tester, you'll hear air coming out.

Another way that sometimes works is on a cold engine, remove the coolant fill cap to make sure there's no pressure, replace the cap, and start the truck. It'll pretty much immediately start to pressurize the tank. That's normally a good indicator as long as your coolant looks normal and not dark or oily. If that's the case, you'll have to do a combustion gas test.

Replacing the compressor head isn't difficult but doing it the right way requires a torque wrench and I always recommend replacing the 2 coolant lines since you're right there and they're prone to breaking. I haven't had a customer deny them yet.

 

You can also disconnect the coolant lines and cover the compressor connections with deflated balloons.
Connect shop air direct to the output side and roll the engine over.
If the balloons inflate that is your reason for pressurized cooling system.

 

What motor ?
MX13 is famous for dropping a liner ....
$$$$$$$$$$$

 

Putting that one away in the brain compartment for future use.

 

third generation knowledge... Thanks Dad