Automotive Air Conditioning Information Forum (Archives)

Provided by

We've updated our forums!
Click here to visit the new forum

Archive Home

Search Auto AC Forum Archives

Oil Migration during Nitrogen Pressure Testing

terryk on Wed July 16, 2008 11:10 AM User is offline

Year: 86
Make: Pontiac
Model: Fiero
Engine Size: 2.8L
Refrigerant Type: R12
Country of Origin: United States

My system uses 8oz of oil. I put 3 in the compressor, 2 in the condenser, 1 in the evap inlet and 2 in the accumulator inlet.

I vacuumed the system and found a leak. I pressurized the system with nitrogen to 90 PSI and found a bad o-ring in the fitting that I forgot (buried under the front end).

I fixed the leak and went to swap the accumulator with a new one, so I drained the oil and found under half an ounce of oil in the accumulator. I drained it for about an hour.

I am assuming the nitrogen pushed the oil out of the accumulator or into the desiccant bags.

Should I just add back in that 1/2 oz and assume it was pushed elsewhere in the system or add back in the 2 oz and assume the oil is actually in the desiccant bags?


JACK ADAMS on Wed July 16, 2008 11:42 AM User is offline


now that you have installed the new replacement compressor, I hope you flushed all the other components prior to the compressor install? The nitrogen will not remove the oil from the accumulator as long as you did not run the car. The accumulator should have been replaced when you did the compressor so all the oil charge capacity is not compromised. The nitrogen will not hurt the accumulator at all so this test could have been done with the new one on. Hope this helps and good luck!

terryk on Wed July 16, 2008 11:50 AM User is offline

The accumulator is going to get changed since the system was opened several times while I hunted down the leaks. For $40 I don't want to risk a future problem.

So given that, any suggestions on the oil replacement?

Edit: I should have answered everything else. The system has a new compressor, it's been flushed and blown out within an inch of it's life. I remove the condenser and evap for the flush (Hecat flush) and gazillions of cubic feet of air. I have a new hose with muffler and OT installed.

When I got the system back together I found a new leak. There is one fitting hidden under the car and when you remove the OT section it really twists that hidden fitting. Once I remembered the fitting, I replace it's o-ring and fixed the leak. However, during the chase the system was opened many times while I checked all of the other o-rings so I am changing the accum just to be safe.

And with that comes the oil question.


Edited: Wed July 16, 2008 at 11:57 AM by terryk

TRB on Wed July 16, 2008 11:53 AM User is offlineView users profile

Drill a hole in the old accumulator and drain it. Add back that amount plus .5 ounce. But it's a guess at this point again.


When considering your next auto A/C purchase, please consider the site that supports you:

terryk on Wed July 16, 2008 11:58 AM User is offline

Ok, thanks Tim.

mk378 on Wed July 16, 2008 12:02 PM User is offline

I agree with Terry. If you didn't run it, the whole 2 oz is still in the accumulator, just soaked into the desiccant bag or trapped in the bottom. So put 2 oz in the new one. You have to drill a hole to more fully drain an accumulator, it won't pour out of the ports.

If you do this again it is OK to just put the whole oil charge into the compressor (if it will fit) and let it distribute itself. The compressor is the only part that needs oil.

terryk on Wed July 16, 2008 12:36 PM User is offline

Thanks Mk, in the Fiero it's a bit hard to keep the whole oil charge in the compressor and get the lines hooked up. You usually wind up wearing most of the oil.

I followed the factory service manual distribution specs figuring that would be as safe as any. I will drill a hole in the accumulator and see what else comes out. I know there is no clear-cut answer here but if I wind up 1 oz over the spec I doubt it will be the end of the world consider the size of the Fiero system.

Edit: No, I didn't run it. It's draining now. Not much is coming out.

Edited: Wed July 16, 2008 at 1:26 PM by terryk

iceman2555 on Wed July 16, 2008 5:44 PM User is offlineView users profile

Not quite sure why the accumulator was 'trashed'...but mk is correct...the lube is in the accumulator..just been absorbed by the desiccant bag.....never could understand why it was necessary to add lube to the condenser....why does it need lube.....the evap....same question.....the compressor needs the stuff....and the accumulator supplies the compressor.....why not there and there and let the system balance itself.
Yes..TRB...that is in the new sheet.
The problem here is how much to add to the new accumulator....what drains out +/- may not be a true indication of a replacement valve....what if none drains out....cut it open...remove bag and squeeze the heck out of it.....naw...too much is known that the first two oz are necessary to saturate the desiccant that two maybe a couple more to insure some lube for the compressor at start up. The extra two should not present a problem as far as an over charge.
Heck there are vehicle on the road today with much more than a two oz over charge.....just imagine how many vehicles are repaired each day and never flushed.....esp those with TXVs located within the air box.....not a suggestion....just a statement of fact.
Just make sure there is lube flow for the compressor at start up.....!!!!
Never been a proponent of adding all the lube to the compressor prior to start up.....the compressor only needs app 25-30% of a the normal lube charge. True it will push it out....but the compressor may run completely dry before there is sufficient refrigerant to return lube flow to the compressor........ esp when charging by cans.

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

CCWKen on Wed July 16, 2008 7:02 PM User is offlineView users profile

I spread the lube out just so the compressor doesn't run dry. It has to make a long trip before it comes back around. The compressor is sucking a lot of dry refrigerant until it gets there. Just my thoughts.

Ken Kopsky

Custom Car Works
"Rules are for the guidance of wise men and the obedience of fools."

Back to Automotive Air Conditioning Forum

We've updated our forums!
Click here to visit the new forum

Archive Home

Copyright © 2016 Arizona Mobile Air Inc.