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Vacuum Pump Oil in AC System. Help!

philoprof on Thu June 06, 2013 5:25 AM User is offline

Year: 1981
Make: Mercedes
Model: 380sl
Engine Size: 380cc
Refrigerant Type: R134
Ambient Temp: 80
Pressure Low: 0
Pressure High: 0
Country of Origin: United States

Well, I just spent the last several days replacing the AC compressor on my 81 380sl. However, when I pulled a vacuum, I mistakenly left the vacuum pump on with the manifold gauges open, which ended up sucking vacuum pump oil into the system.

Although I'm not sure how much oil got sucked in, it took app 150 cc of oil to bring the level in the pump back up to where it was before the oil got sucked up. So, now I'm wondering which of the following is my best option:

1) Run the AC and hope that the pump oil won't damage anything;
2) Take the system apart again, remove the compressor, replace the oil in it, and flush the hoses, considering the time and effort that doing this will require;
3) Try to remove the oil some other way;
4) None of the above.

Thanks in advance for any advice anyone can give me.

Bill
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NickD on Thu June 06, 2013 8:07 AM User is offline

2) Take the system apart again, remove the compressor, replace the oil in it, and flush the hoses, considering the time and effort that doing this will require, plus replace the dryer.

philoprof on Thu June 06, 2013 10:14 AM User is offline

Quote
Originally posted by: NickD
2) Take the system apart again, remove the compressor, replace the oil in it, and flush the hoses, considering the time and effort that doing this will require, plus replace the dryer.

Thanks for the quick reply, Nick, even though I was afraid to hear what you said.

But let me ask you another question: since I haven't run the system, is there anyway of knowing whether that oil could have gotten into the condenser, or all the way up into the expansion valve and/or evaporator coil, and whether flushing the system could damage either of those things. The reason I'm asking is that replacing the coil in these cars involves taking the entire dash apart, and that's something I'd like to avoid at all costs if possible.

Thanks in advance for the additional advice.

Bill

TRB on Thu June 06, 2013 12:41 PM User is offlineView users profile

I wonder how a device sucking, injected oil into the system?

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philoprof on Fri June 07, 2013 5:46 AM User is offline

Quote
Originally posted by: TRB
I wonder how a device sucking, injected oil into the system?

When I shut the pump off after establishing a vacuum, the vacuum sucked oil from the pump up through the open ports on the manifold gauge into the system because, as I found out later, that model Mastercool pump doesn't have a valve to prevent that from happening :-( .

NickD on Fri June 07, 2013 6:25 AM User is offline

What I read was an R-134a conversion to an 1981 Mercedes that would require PAG oil. Assumed the pump was killed before closing that valve. Then that bit about switching hoses, tips section on this board gives means to work around this. You never want to switch hoses when going from vacuum to charge.

With my old stuff, still sticking with R-12, but kind of thinking about getting rid of it as getting old myself. By some miracle just had life saving surgery done last Monday or will be joining Mitch.

With an evaporator if can be accessed from the firewall side and jury rig hoses and use NAPA lacquer thinner to flush it out. Then blow it out well. If this is a first time conversion, may not be happy with the results, tube and fin condensers don't work very well with R-134a unless that was changed.

philoprof on Fri June 07, 2013 1:24 PM User is offline

q]Originally posted by: NickD
What I read was an R-134a conversion to an 1981 Mercedes that would require PAG oil.
The system was converted to R134 a number of years ago. I was just replacing the compressor because it was 30 years old, and it sounded like the bearings were going on it.

> Assumed the pump was killed before closing that valve.

Yes!

>Then that bit about switching hoses, tips section on this board gives means to work around this. You never want to switch hoses when going from vacuum to charge.

No. I didn't switch hoses. I just turned the pump off without closing the ports in the manifold gauges. So the vacuum pulled the oil from the pump into the system.

> With my old stuff, still sticking with R-12, but kind of thinking about getting rid of it as getting old myself. By some miracle just had life saving surgery done last Monday.

> If this is a first time conversion, may not be happy with the results, tube and fin condensers don't work very well with R-134a unless that was changed.



I don't think that the PO changed any of those things, but the system cooled pretty well anyway.


philoprof on Sat June 08, 2013 7:21 PM User is offline

I don't want to belabor this thread. But I just recalculated the amount of vacuum oil that entered my system, and it's less than 100 c.c.. So, I was wondering whether that changes the situation any, as I obviously don't want to have to take the system apart if I don't have to.

I was also wondering 1) how far that oil would have gotten pulled into the system, considering that I didn't run it, and 2) what the possible and probable downsides would be if I do run it with the vacuum oil in it.

Thanks in advance for the advice, guys, as this is the first time I've dealt with something like this

Bill

mazda626awd on Sat June 08, 2013 9:38 PM User is offline

Nick D. I'm in the market for some R12 if you are considering getting rid of it. I got 6 R12 systems in my inventory. 3 on the road and 3 spares.
Thanks
Dave in VA.

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