Pulling a vacuum for a/c conversion
Thread Starter
Le Mans Master
Joined: May 1999
Posts: 6,692
Likes: 29
From: Texas
Pulling a vacuum for a/c conversion
How about hooking up a hose to the low pressure valve and the other end to a vacuum port on the manifold. Yeah, so I am pulling freon, oil and moisture through the manifold. Is that any different than a PCV valve?
Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
I've done that. It will get the air out, but will not boil out any moisture since you need 28"hg or better to remove moisture. Getting the air out is a must.....If you live in a dry climate and the system hasn't been open too long moisture shouldn't be a problem. I don't know what will happen to you Catalytic coverter though. They are sensitive to lots of stuff.
Melting Slicks
Joined: Apr 1999
Posts: 2,521
Likes: 4
From: Windham, NH
Originally Posted by Larry82
Yeah, so I am pulling freon, oil and moisture through the manifold. Is that any different than a PCV valve?
Instructor
Joined: Dec 2002
Posts: 242
Likes: 0
From: Port Orchard Washington
Both R12 and R134a turn into Phosgene (re:nerve) gas at temperatures above 260 degrees. If you do this, please don't do it in a garage.
Although 28" is best to remove the majority of moisture, the GM shop manual only requires 14" for 45 minutes. This assumes that any additional moisture will be assimilated in the dessicant bag of the receiver/drier if it is not already saturated. So technically you could evacuate your AC system with manifold vacuum. Personally, I would not recommend it because of the availability of cheap sources of vacuum pumps (Harbor Freight, auto parts rental, etc.)
My .02
Although 28" is best to remove the majority of moisture, the GM shop manual only requires 14" for 45 minutes. This assumes that any additional moisture will be assimilated in the dessicant bag of the receiver/drier if it is not already saturated. So technically you could evacuate your AC system with manifold vacuum. Personally, I would not recommend it because of the availability of cheap sources of vacuum pumps (Harbor Freight, auto parts rental, etc.)
My .02
