I have 2 GMC trucks with expansion valve leaks

[Bob F.]

So first GMC Sierra came in not cooling. Blowing warm air. I charged the truck and checked the condenser. It was fine. Then I sprayed soapy water up on the expansion valve and it was bubbling fairly strong. I went ahead and changed the exp. valve. Probably didn't have to, but did anyway. After installing valve I pressured system to 250 psi with nitrogen. Checked the valve for leaks and found nothing. Evacuated and charged. Started truck up. Ac working well. I went around and went ahead and used soapy water on the valve with system operating. Expansion valve still making bubbles big time. Pulled the charge and removed exp valve. All sealing washers in place. Repeated the operation again. Good cooling and still blowing bubbles. Some from the front flange and some coming out from inside the plastic cover.
Then a 2015 Yukon comes in after the customer changed out his system himself. I pressure tested system. Evacuate and charge. Expansion valve blowing bubbles also.
I've done a whole bunch of Gm condensers and several expansion valves. This is a first for me. Also very odd it's happened two times in a row. Anyone seen this before?
Id say bad evaporator but both systems hold 250 psi for 45 minutes or more. Both trucks do not leak until the AC system is engaged.

[Tom Greenleaf]

? GM parts or if known aftermarket? Two pulling same bull different trucks. Let's see what others say or just terrible bad luck. Only while engaged too?? I'm still thinking so far nothing................

[muscle spasm]

Best method to check for leaks is under pressure. 150 PSI is fine.

I would bubble test every hose, service port and connection you can find. Every line and so on. Do this in a garage with no air flow if possible. Run your fingers over the lines. Listen for any weird noises like leaks.

Nylog every o-ring, service port and schrader valve as well. Nylog is your friend.

Those gm trucks normally leak at the condenser on both sides. I would look there as well.