Oil Balancing System

Information on some common auto air conditioning topics.
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MeteorBurn
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Oil Balancing System

Post by MeteorBurn »

Hello everyone,

Hope everyone is doing good.
Thought I'd try my hand again at fixing the A/C in another older family car after I had good results with the last repair I did on another vehicle.
The advice I received here was quite helpful.

Vehicle: 1995 Oldsmobile Cutlass Supreme
Engine: 3.1L, V5 Compressor

The main issue it had was a refrigerant leak, traced back to the high side port with the rubber ball GM uses, along with some oily residue on the compressor body which I assume to be a shaft seal leaking. My leak detector probe did not go off near it but I'd rather not risk doing the job again and a new OEM compressor was not as expensive as I expected, so I went ahead and bought another one. I also purchased new o-rings for the whole system, a new accumulator, high and low side port, and suction/discharge hoses for the compressor. I also bought a new condenser as the old one was badly bent in a front end collision (was not leaking, but wanted to be on the safe side).


According the service manual, the system capacity is 8 oz. They specify the following capacities:

Compressor - 2 oz if less than 1 oz was drained from old one, same amount as the old one if more than 1 oz was drained.
Condenser - 1 oz
Accumulator - 1 oz + what you drained from the old one.
Evaporator - 3 oz



The condenser is new, so that received 1 oz.
I drained about 1.3 oz from the old compressor, so that's what I put back into the new one after draining it.
I drained almost nothing from the accumulator, so I assume I need to add 2 oz back into it (to reach 8 oz total)
Evaporator is not being changed or flushed, so can I assume it has roughly 3 oz?
The manual claims small refrigerant leaks do not result in oil loss, but I feel as though I will not be at the system capacity when I finish adding the oil.

Is my approach correct? Any help is greatly appreciated.
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JohnHere
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Re: Oil Balancing System

Post by JohnHere »

According to the GM specs, you need a total of 8 ounces of oil in this system for the V5 to remain "healthy." As I see it, the only problem with your approach to balancing is that none of us knows how much oil, if any, remains in the original evaporator.

Since you have replaced everything else with new components, I would at least flush the evaporator so that you can start with a completely empty and clean system. Then I would distribute the oil as follows:
—3 ounces in the compressor (3 ounces seems to be what most new V5 compressors come filled with),
—1-1/2 ounces each in the condenser and evaporator, and
—2 ounces in the accumulator.

I'm not sure whether the V5 can take all 8 ounces of oil. But if so, you could also put all of it in the compressor. Many cars' A/C systems are done that way on the assembly line.
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DetroitAC
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Re: Oil Balancing System

Post by DetroitAC »

I agree with John mostly, nobody knows how much oil you have, GM doesn't know, those guesses are just based on some repair studies and are gross generalizations. I've had to make those guesses myself, they are wild ass guesses, kind of statistical rules of thumb. It's better to tell a technician to add 2oz than to say nobody knows, the technician might add oil, which is a good thing.

I would put at least 8oz in, GM is playing the numbers putting in as much oil as needed to keep warranty down, and not too much because oil costs money. For my money, I'm willing to suffer a 0.2 degree less vent temperature and I never want to replace the compressor again. I would not care how much was really in the evaporator, I'd add oil conservatively to make sure it's reliable.
MeteorBurn
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Re: Oil Balancing System

Post by MeteorBurn »

Thank you for the replies.

Yeah, that's pretty much what I figured - these are just generalizations GM made based off some ballpark measurement. Who knows how much oil was really in there the past 10 years or so.

I would like to attempt flushing, but I'm not sure I could do a good job without removing it from the car. Dash has to come out for that so I'm really not too keen on doing that, and my garage is already quite a mess from another car I have sitting on jack stands in the garage.
Could I get one the flushing tools you'd hook to a compressor, and flush it in the the car, and chase it down with lots of compressed air? I'm just worried I would leave an oil/solvent blend that I could not get out without tipping it around, shaking it, etc.

Otherwise I might just go ahead and add 2.5 oz to account for the evaporator and leave a .5 oz error margin for some that might still be in there. I would rather overestimate slightly so as to not ruin the new compressor in the long term.

Apologies if I am being a worrywart, I just want to get this right and not touch it again.
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JohnHere
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Re: Oil Balancing System

Post by JohnHere »

MeteorBurn wrote: Thu Jun 30, 2022 3:15 pm I would like to attempt flushing, but I'm not sure I could do a good job without removing it from the car. Dash has to come out for that so I'm really not too keen on doing that, and my garage is already quite a mess from another car I have sitting on jack stands in the garage.
Could I get one the flushing tools you'd hook to a compressor, and flush it in the the car, and chase it down with lots of compressed air? I'm just worried I would leave an oil/solvent blend that I could not get out without tipping it around, shaking it, etc.
If you can access the inlet and outlet tubes, I would flush the evaporator in situ rather than dealing with all the work necessary to R&R it or replace it with a new one. You didn't have a catastrophic compressor failure, so you only need to clean-out the old oil residue. To do that, you don't have to spend a lot of money for professional tools.

ACKITS.com, this site's sponsor, has what you need in stock (Part Number 43-4054) to do a thorough evaporator flush. Be sure to use a solvent specifically formulated for mobile vehicle A/C systems that will evaporate quickly and leave behind no residue. One gallon, maybe less, would suffice for flushing just the evaporator. On the same page as the part number listed above, ACKITS.com offers a choice of special solvents for that purpose. Contact Tim for additional information and ordering.

After flushing, blow-out the evaporator both ways and several times with shop air—the drier the air the better—until you see no more liquid solvent coming out. Once you're satisfied that all the solvent has evaporated, go ahead and distribute the PAG oil as previously discussed and reassemble everything using the new o-rings. A little Nylog Blue applied to each o-ring and joint will help ensure a leak-free system.
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MeteorBurn
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Re: Oil Balancing System

Post by MeteorBurn »

Thank you again for the help.

That sounds like a plan, I went ahead and found some rubber hoses that fit nicely over the inlet and outlet pipes from the evaporator that I will use to redirect the flush chemical. I will report back how I make out.
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