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Oil in compressor


New Member
July 7, 2009
Reaction score
City, State
Phoenix, AZ
Year, Model & Trim Level
'98 XLT 5.0 2WD

Have 98 XLT 5.0. Just replaced the compressor, condenser, orifice tube and accumulator. Followed instructions from this forum, and it all worked out quite well. Thx!

Some questions arose for me:

There are a number of slightly different takes on how to handle the oil for the compressor, so I feel a bit confused. First, I've got cold air, my pressures are 28-205 in 95 ambient. With engine running ac 'settles' after a few 10 minutes of compressor cycling on/off every few seconds.

The only challenge seems to be that the compressor is operating louder than the one I replaced, and it seems to have a bit of a metal sound (mild) to it. My concern is that I did not apply oil to the compressor properly.

The Haynes manual indicates that I needed to empty the old compressor of oil, measure it, then:
- if less than 3 ounces, add 3
- if between 3-5, add that amount plus 1 ounce
- if over 5, then add that amount back

I've seen in this forum that some compressors come pre-filled with enough oil, but I've also seen that too much oil is a problem.
The new compressor came with just shy of 5 ounces.
The old compressor had no oil...
I chose to follow the manual, so I added back 3 ounces of oil. Also, I added the oil back into only the high side opening (i recall now, dumb moment? will blame it on working in 108 degrees today.)
I put 1 ounce in the condenser, and 3 ounces in the accumulator, per the Haynes directions.

Q1: Did I add enough oil back into the compressor?
Q2: Did I need to add oil into both high and low side openings?
Q3: Will the system balance the oil?
Q4: If no, yes, and no respectively, then what may happen if I drive for 48 hours before I take it apart again to add the right amount of oil?

Hope this makes sense.
And thanks in advance for feedback/answers!


Refrigerant oil in the system...

Most modern compressors do not have a reservoir to hold oil... The refrigerant oil circulates with the refrigerant and lubricates the components so adding oil to the high side only is non-consequential...

Now to address your concerns... The compressor gets lubricated as the refrigerant flows through so the oil in the system "equalizes" as such.. There is no real seperation between the high and low sides of the system and this is why the pressures balance when the compressor is not turning..

As far as the noise is concerned, is this a remanufactured or new compressor? Are all the mounting bolts tight and nothing touching the compressor or mounts that might vibrate? Or is the compressor touching another part of the engine and setting up a resonance through that contact?

With the pressures at 28 lo/205 high you actually seem to be a little undercharged going on the 2.3-2.7x ambient for the high side...I would ask too if the fan clutch is in good shape or is it marginal and need replacing at this point too???

It sounds like you might have gotten a compressor with looser tolerances than the old one.. That is not necessarily a bad thing but if you have a warranty on it I wouldn't pull the system apart at this point since you did install enough oil in the system, the system is working, and, depending on the high/low pressures while running, the system is operating within normal parameters...

I guess my first question to you should have been did the first compressor die from black death necessitating the almost firewall-forward parts replacement?

Thanks, you've confirmed for me that I was thinking about the system in the right way overall.

Initially, I did not know what was wrong. The XLT has 200,000 miles on it. The A/C has been out for two years (brutal summer driving), and the last time it worked was due to a couple quick charges with additives, etc, which lasted a day or three. For these reasons and for wanting to learn how to rebuild this system, I went ahead and replaced the parts I indicated. I figured I would learn what happened to the system in the rebuild process.

No black death was found. The system was surprisingly clean. But am not sure where the leak was; though the old accumulator was looking like a mummy.

Got all new parts from ackits.com at their local location here in Phx. So a difference in tolerances makes the most sense to me. Will check for other vibrational elements.

I also agree that the system seems to be a bit undercharged. The 2 - 12oz cans did not completely empty, and the a/c capacity is apparently 22 oz. Will top it off today.

And the fan clutch is working well.

Thanks again,

two summers in Phx with no ac! Dude! That's rough I'm currently suffering in East coast humidity with parts in route and trying to get smarter.