Do the engine have to be warm to check for coolant leak with a radiator pressure tester?
To check for a coolant leak with a radiator pressure tester, the engine does not have to be warm. In fact, it's safer to perform the test when the engine is cool to avoid the risk of burns.
Here are the general steps to perform a coolant pressure test:
Make sure the engine and the system is cool since hot coolant can burn, and that the cooling system has no pressure.
If the coolant level is low, add water or coolant to raise it.
Remove the radiator cap once the system is cool and depressurized.
Connect the pressure tester to the coolant reservoir or the radiator.
Pump the pressure tester to apply pressure to the cooling system without going over the system's psi number on the radiator cap, which the pressure tester's gauge measures.
If the pressure gauge drops quickly, there is a leak. The slower the gauge drops, the smaller the leak.
As for your Buick, it's possible that the intake manifold gasket is leaking coolant. This is a common problem in many GM vehicles, including Buicks34. The coolant can leak externally, or in some cases, it may leak internally, causing coolant to mix with the engine oil. Operating the engine with a coolant/oil mix can result in internal engine damage. If you suspect this is the case, it's recommended to get it checked and repaired by a professional mechanic.