Vacuum problem

[georgedunham]

I have a 98 GMC K1500. Compressor has had a very slow leak, I’ve gotten 2+ years on a charge before I need to do it again. I decided that I was done with that, and replaced everything except the evaporator.
Everything went well, except when disconnecting the manifold from the low pressure port, the valve allows air into the system.
I should add that I’m planning on having a local shop do the recharge, so the manifold is being disconnected under vacuum.
My question is this
Is this normal? The valve normally experiences pressure, not vacuum.
Maybe all is well, or maybe I need to return that component and reinstall the fully functional one that I removed.
Help please!
The component in question is GDP purchased from Rockauto, and the valve appears to be non-serviceable.
Thank you in advance
George

[Tom Greenleaf]

? Begs the question why did you replace the last one? This should have been a Delphi OE new it was called a belly leak was a common issue/problem a fav replacement was by Sanden.

How are you so sure it's the compressor not being fooled by the service ports?

They need the OE grade caps as final seal.

Hope you have dye in it AYOR at the age messing with caps if known not GM OE it's a misleading where the leak is.

Look inside a cap for UV dye still see with without a UV light.

IDK, by rights you should (IMO) leave that high side port out checking things just vac+ charge these are easy. If warm enough you can do this with the little cans, 12 oz - send it out if wish for diagnosis decide DIY it or not.

Available at some chain parts outlets is rental (free for safe return full deposit.

Your call some places TMK don't allow renting of A/C equipment??

I doubt you can rent a sniffer for refrigerant would be handy test Shader or perhaps a ball valve on high side?

[bbrickson]

[QUOTE=georgedunham;n4207]I have a 98 GMC K1500. Compressor has had a very slow leak, I’ve gotten 2+ years on a charge before I need to do it again. I decided that I was done with that, and replaced everything except the evaporator.
Everything went well, except when disconnecting the manifold from the low pressure port, the valve allows air into the system.
I should add that I’m planning on having a local shop do the recharge, so the manifold is being disconnected under vacuum.
My question is this
Is this normal?


Vacuuming, then removing the gauges before recharging? No, not how it is done. But what you want to know is that the black ball type of valve can be replaced with a schrader valve. Not just the schrader itself, look closely, the top 1/2 inch unscrews and you can replace it with an improved design. Ranshu.com

The valve normally experiences pressure, not vacuum.
Maybe all is well, or maybe I need to return that component and reinstall the fully functional one that I removed.
Help please!
The component in question is GDP purchased from Rockauto, and the valve appears to be non-serviceable.
Thank you in advance
George[/


Vacuuming, then removing the gauges before recharging? No, not how it is done. But what you want to know is that the black ball type of valve can be replaced with a schrader valve. Not just the schrader itself, look closely, the top 1/2 inch unscrews and you can replace it with an improved design. Ranshu.com

[Tom Greenleaf]

NO, plain wrong. Use on this truck high side when full vacuum is achieved and holds add as it still has a high side port till pressure (any) is noticed on low side you then know air isn't in it NOR the gauge hoses, vacuum them out too.

To A/C air is the enemy - learn that,

[bbrickson]

I was writing about changing the factory ball type service port that always leaks to a schrader type. I included pictures of both.
You are correct that air is not wanted in the system. That is the very reason why you don’t disconnect your gauges after pulling a vacuum. The only thing that is possible is that air will get sucked into the system. Just like when you disconnect your gages from a pressurized system and you hear the pressurized refrigerant leaking while you do that. In a vacuum the opposite will happen, air is sucked in.