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Trapped oil

Ruger 9 on Thu July 10, 2008 2:40 PM User is offline

Year: 1992
Make: Chevy
Model: C2500
Engine Size: 5.7
Refrigerant Type: R-12
Ambient Temp: 80* F
Pressure Low: 34
Pressure High: 170
Country of Origin: United States

Hello All,
I rebuilt the system about 6 weeks ago, replacing everything but the evaporator. The compressor began locking up upon starting, first thing in the morning. I was able to free it up by removing the belt and after engaging the clutch, rocking the shaft back and forth a few times. After that, the system worked good the rest of the day. I now have the system apart again and have been able to recover only 4 ounces of oil from the compressor, condenser, accumulator, hoses and tubing. The orifice tube had a little fuzz on it and a few shavings, but really was relatively clean. I have a new compressor and accumulator on the way. As before, the evaporator will stay put.
I am concerned why I was able to recover only half of the original 8 ounces of oil. How much oil would be carried with the recovered gas? Could there be a that much left in the evap?
The forum is an incredible source of information, with a lot of good guys eager to help.
Thanks for your help.

GM Tech on Thu July 10, 2008 3:14 PM User is offline

Not too bad- most would not try to add up all the oil--- The evap holds a fair amount-- anywhere where the refrigerant was cold- when the refrigerant was pulled out is where the oil will linger.. That was a valiant effort to see how much you can "pour" out of individual components- yet flushing is the only way to assure all oil is extracted- due to the shape of coomponents you need not be concerned that you did not get it all by pouring......

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Ruger 9 on Thu July 10, 2008 4:30 PM User is offline

Thanks GM Tech. I've had the condenser hanging fittings down for about 12 hours then air popped it a few times. I think it is empty of oil. I'm going to flush the evap, blow and pop, then let it dry a few days and call it good. Whaddaya think, Tech? Thanks so much for the help.

terryk on Thu July 10, 2008 4:33 PM User is offline

I am curious, how much oil was in your accumulator?

Ruger 9 on Thu July 10, 2008 4:48 PM User is offline

I poured slightly more than an ounce from the accumulator and it does not feel overly heavy as though the bags are saturated.

terryk on Thu July 10, 2008 5:02 PM User is offline

Interesting, thanks!

bearing01 on Thu July 10, 2008 6:53 PM User is offline

If your evaporator was oil logged then you'd probably get poor cooling because it would be insulating the refrigerant from the tube walls and absorbing heat.

When the compressor locks up does the belt squeel? What happens?

Sounds to me either a mechanical failure or the compressor is getting hydro-locked on startup. Maybe the refrigerant is overcharged? And the accumulator is completely full? Or liquid is flooding backwards from the condenser? When running on the cooler days does the accumulator feel cold all the way from bottom to top?

That or perhaps there's a problem with the clutch itself (seized?) that's causing the pulley to jam?

Ruger 9 on Thu July 10, 2008 7:30 PM User is offline

I was able to get 42 degrees at the center vent on a mid 80's day. Unfortunately I was not able to watch the compressor during startup and lockup, but when I would engage the clutch from the cab, I would get a nasty metal to metal hammering and vibration as though the compressor shaft was rocking back and forth. At that point, I would immediately disengage the clutch shut off the engine, remove the belt, and rock the engaged pulley a few times and with no noise it just frees up like nothing happened. It did not feel spongy like a hydro lock, but a dead stop like a mechanical lock. The compressor was a new Delphi R-4. The supplier said he would let me know what they found when opened up. I have already received a replacement (a new 4 seasons). I know I must flush the evap of residual oil, but don't want to go though flushing the condenser if possible. I may have overcharged by a few ounces (3-4), but then recovered 42ounces in the recovery tank.
Thanks so much, bearing.

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