Automotive Air Conditioning Information Forum

I just replaced the compressor, accumulator, and orifice tube in my 1998 Explorer. Everything went very well up until it came time to recharge. I couldn't seem to pull vacuum past 24 in Hg. After much troubleshooting, using 3 different vacuum pumps, I found out that being at 5300 ft of elevation would reduce my gauge reading by about 5 in Hg. So I figured I had pulled adequate vacuum, but just to be sure I drove around until the car got nice and hot, ran the heater to heat up the evaporator, then put it back on the vacuum pump for an hour to be sure all the moisture had boiled off. That was probably overkill, and probably what led to my problem.

The first indication of a problem was a bit of oil frothing out when I purged the fill line of air. Didn't think too much of it and proceeded to fill the system with the required 28oz of refrigerant. Air was blowing nice and cold, and the pressures looked good, so I started to pack it in. This is when the issue became apparent.

After unhooking the manifold gauges, I went to purge the refrigerant remaining in the manifold lines. No problem with the low side, but as I started to release the high side, me and my engine bay got a frothy oil shower. I'm not sure how to describe or quantify how much oil came out, but it was a significant and surprising amount. I immediately re-closed the valve, so there is still about 100 psi and what I assume to be a lot of oil in the high side line.

FYI, I put 5oz of PAG 46 in the suction port of the new compressor and gave it a few turns by hand before installing.

Any ideas of what happened here and how to proceed? Did I really vacuum up that much oil, or did something else happen?

I am thinking I need to somehow capture and measure how much oil is in the high side hose, or else try to force that oil back into the system so that I have the proper amount of oil in the system. Thoughts on the best way to go about this?

Looking forward to the replies. Thanks!

Here is what came out of the high side charging hose:

After more thinking and more researching, I think I found out what I did wrong. At some point I must have shut off the vacuum pump before closing the valves, and the vacuum present in the system sucked up oil from the pump, like the person in this thread: http://acsource.net/acforum/viewtopic.php?f=1&t=8237. Makes sense that the yellow color of the oil above looks more like vacuum pump oil than the clear PAG oil I put in. I don't like the look of whatever else is in there though. Well, I guess I learned my lesson, and hopefully this helps someone else...

Always be sure to shut off the valves before turning off your vacuum pump!

If your vacuum pump oil is yellow, you need to change it.

It was that yellowish color right out of the bottle. Brand new oil for this job.

karb wrote:After more thinking and more researching, I think I found out what I did wrong. At some point I must have shut off the vacuum pump before closing the valves, and the vacuum present in the system sucked up oil from the pump, like the person in this thread: http://acsource.net/acforum/viewtopic.php?f=1&t=8237. Makes sense that the yellow color of the oil above looks more like vacuum pump oil than the clear PAG oil I put in. I don't like the look of whatever else is in there though. Well, I guess I learned my lesson, and hopefully this helps someone else...

Always be sure to shut off the valves before turning off your vacuum pump!

Yeah, also if you ran your vacuum pump, isolate the system and for some reason decide to vacuum more. In that case run your pump for a while or as soon as you open your valves up, it'll suck the oil from the pump.

wptski wrote: Yeah, also if you ran your vacuum pump, isolate the system and for some reason decide to vacuum more. In that case run your pump for a while or as soon as you open your valves up, it'll suck the oil from the pump.

Oh, that makes sense. I made that mistake several times, which is probably the source of the oil. Good to know, thanks.

I read that vacuum pump oil is mineral oil, which is not miscible with r134a, so I'm hoping it just drops to the bottom of the system and doesn't cause any issues down the road.

karb wrote:Oh, that makes sense. I made that mistake several times, which is probably the source of the oil. Good to know, thanks.

I read that vacuum pump oil is mineral oil, which is not miscible with r134a, so I'm hoping it just drops to the bottom of the system and doesn't cause any issues down the road.

Me too until I figured out what I was doing wrong. If your hoses are situated with a low hanging spot the pump oil will accumulate at that point, partially block the hose but not completely and probably not make it into the system. I probably did that on one vehicle and a dehumidifier, neither had operation problems once fully charged.

I have now have a nitrogen setup so if I want to vacuum two more times which is called sweeping the system, I break the vacuum with nitrogen before starting the vacuum process again.