[Tom Pugh]

I have rebuilt the ac system in my '67 goat and plan to purge it prior to charging it with R12. I filled the compressor with fresh oil. Will it get sucked out when the vacuum is applied? Also, how much vacuum is needed for the job? Thanks

[nas t eh]

You may want to have a shop do this part. But there are books and videos available.

To do it right you need to get all the air out, that requires 28 inches of vacuum. Yes all the oil will come out too. You should block in the vacuum on the system and check that it holds vacuum as well before charging the system.

I have seen it done with a regular air compressor with a fitting and a valve on the inlet side of the compressor, but I have only ever topped up mine or friends systems never started from scratch with an empty system that needed evacuation. Do you have access to a set of AC gauges?

[indymanjoe]

I don't think the oil will come out.28inches is all you can really get on a vacuum pump. pull it down to the 28 let it sit for awhile and see if the pressure rises. if it does you still have a leak. if not weight it in or use a charging cylinder. Its really not a hard job to do.

[bhill86]

Agreed. I charged my AC system and pulling a vacuum won’t remove the oil.

[tstroud]

I also agree on 28 inches. Let the vacuum pump run for about 30 minutes. Then close the hose to the pump off and let it sit for another 30 minutes. If it holds, fill it. If it doesn’t hold, fix your leak and repeat.

[66sprint6]

I rebuilt my A/C system in the LeMans last year. I did not find it to be difficult at all. I was lucky I scored a 30lb bottle of R12. Cleaned everything up, replaced every O-ring, closed it up, pulled the vacuum, confirmed no loss of vacuum, then weighed the R-12. It blows cold alright.

Edit I forgot to mention a new dryer of course.

[Goatracer1]

If you didn't replace the hoses you should. 50 to 60 year old hoses will seep. Better to do now if you haven't than have to do it later.

[burd]

I see R 12 at the swaps all the time. It’s getting easier To get it seems.
An old timer was selling GM AC oil too. Bought a couple

[DANTIP]

Deep vacuum is measured in microns. In order to have a leak-free and dry system, achieving 500 microns will do the job. I STRONGLY suggest your system be evacuated to this level if you plan to use R-12 (which I very much like).

The deep vacuum verifies your system is dry and leak-free. Any good HVAC tech has a micron gauge and a suitable vacuum pump to do the job.

Good Luck!

[AG]

I agree with 500 microns, which takes a good vacuum pump. That equals 29.9003" Hg.