AC question...again

[Nick Triesch]

Sorry, I know I keep asking. Does all the AC oil in the compressor leave the unit after it is run and just stay in the hoses and components? or do a few ounces remain in the unit after it is turned off? I removed the compressor because of a leak and turned it over to pour out some oil and not a single drop came out. I tried to pour it out from the main connection points. Thanks.

[Rawknees'Turbo]

Nick, in my experience, most of the oil in the system remains/collects in the compressor - it spreads out and moves though the components during operation, but the compressor always has the most oil in it of any other component in the system once shut down.

Hard to explain why yours doesn't have any oil in it.

[Hoppe]

It lubes the whole A/C system. Mine was the same when I drained it. Very little came out of the compressor. More when I flushed.

[kuehl]

Let's assume 'a system' which has never had any leaks, and has an oil capacity of 5 ounces, and has the following components:

1 compressor,
2 condensers,
1 evaporator with TEV (expansion valve),
1 drier,
40 feet of ac hose.

When the system is operating the oil is 'moved' through the system by the refrigerant. Without a sufficient flow of refrigerant, the compressor will never get lubricated; the refrigerant is the train carries things along.

When the system is turned off the oil 'settles' because of gravity.

The design of the compressor is 'sumpless', it has no oil tank .

What tends to happen is certain components, because of their structure and volume, they accumulate more oil than others. For example, the evaporator, because of the number of tubes or channels can retain more oil after things settle than a compressor.
A drier, because of its structure and purpose to retain refrigerant, can retain more oil than a compressor. Condensers not so much as evaporators. Again, it all depends upon the component's physical design and internal volume.

Compressors, in my experience with the 911 and 930, might hold (in the case of a fully charged; refrigerant and oil, leakless system) 1 ounce. And, this ounce will be cling inside the internal structure and will be difficult to drain out. If you remove the compressor and orientated it so its ports are over a clean coffee can, and turned its outer hub several times in both directions, and tilted is left from 'bow; clutch end' to 'stern'; opposite back end, you might extract 1 ounce. And, that quantity might be related to the viscosity of the refrigerant oil and as well as ambient temperature.

If you removed the evaporator from this system, and took off its TEV, and you were able to 'flush' out its oil and separate from the flushing solution, you might find 1.5-2 ounces.

If you were to remove the evaporator outlet to from compressor inlet hose from under the RH side of the car, you might find 1 ounce settled in the hoses lowest point (gravity). Ditto on the rear deck lid condenser to front condenser. The front condenser .5 to 1 ounce. And so on.

Getting back to your observation of your compressor having little or no oil. Try the 'tilting over the clean coffee can, turning outer clutch hub, tilt bow to stern' thing and see if anything comes out. If not, it could be the system has lost oil over time due to system leaks. While you are at it, take a clean cotton q-tip and do the swab test. Swab in inlet and outlet ports of the compressor and examine the swab with 5x magnifier. If you see dark grey matter or metal particles then its time to take the compressor apart and examine its internals for wear.

Ditto the swab test further north in the system following the flow of refrigerant (compressor to condensers to drier to TEV). If anywhere along the way you find debris or 'dark matter', its time to consider whether things need to be liquid AC flushed and replaced (driers, compressors).

[Nick Triesch]

Thanks Kuehl! You know your stuff!

[kuehl]

You get smart when you drink snake oil