Autozone gave me a 1.8 cfm vacuum pump adn i am wondering if this is big enough to evacuate my system. If so, how long should it be done for if system has been flushed and lines only sat open overnight.

 

I mean, 0.1 cfm is enough, it'll just take a long *** time. a 1.8 should take about 10-12 minutes (2002 civic). Use the gauge set, vaccuum from low and high side until the low end reads -20 consistently. Turn the pump off and make sure it holds -20 for 15 minutes. If it does, refill. If it doesn't, fix the leak, evacuate again, and refill.

CFM is cubic feet per minute. It's a rate, or speed. So slow still works but it'll just take longer.

 

normally you wanna evacuate for about an hour, but half hour atleast

you should also replace the receiver/drier

 

Huh, @holmes my whole evac took about 15 min maybe at most, did it on a lunch break...

 

15 minutes is not enough, but you're welcome to do it for however long you want to do it

 

Great, now you got me worried.

 

you'll be fine, it's not going to be a major issue

 

No

3 cfm is the minimum with 5-6 cfm being optimal.


The system should be vacuumed for 45-60 mins @ 3 cfm.

The point of vacuuming the system isn't to draw out air,it is to boil off moisture,which is the most harmful aspect of leaving the system open to atmosphere. Even at 3 cfm the pump will have a hard time boiling off all of the moisture.

 

Welp, guess my 1.8 cfm job didn't work, even though I successfully charged my AC with it.

 

Know what happens when you run pure water instead of 50/50 antifreeze mixture in your cooling system?



Nothing happens......



.......for about 5 years or so,until you begin to get multiple failures in the cooling system from the build up of oxidation, scale and cavitation.


Same deal applies here. Its fine until it isnt......

 

Well I pumped until no more steam was coming out of the pump's vent and made sure it held the vacuum there at -20 hg for 15 minutes before charging. For future reference, and for the sake of any other people I try to help, when should I have stopped? (2002 civic Si)

 

1 hour

 

Agreed.



The common school of thought is, 'the longer the better' but 45-60 mins is the accepted industry standard(@ 3cfm)

 

Noted. I'll go capture and re-vacuum, thanks for the info.