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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Bill
1981 380sl

Some vacuum pumps use oil rather quickly. If its pulling a vacuum, then there is no way for it to be pushing oil from the pump into the system. Are you sure the pump didn't simply burn through the oil?

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Yeah, I'm pretty sure. I called Mastercool, who manufactured the pump, and the tech told me that the model I was using, which I got from Autozone, didn't have a valve that would prevent the oil from flowing into the system if the pump was turned off while the system had a vacuum, and the manifold gauges were still open. Yikes!

I never did this before and the instructions that came with the Harbor Freight manifold gauges didn't clearly explain what ON and Off meant on the handles. So, I mistakenly left turned the pump off after I pulled a vacuum and the system was still open.

I recall hearing a gurgling sound, and I saw the oil level going down in the sight glass, but I didn't realize what was happening until it was too late.

Replacing that compressor on this 107 was a real PITA, because it required removing the radiator, the fan, the PS pump, the PS bracket, the crankshaft position sensor. Plus two of the Allen head bolts were so tight that they stripped.

I imagine that taking the compressor out won't be as hard the second time around. But, if there's some way to avoid that, I'd like to know what it is.

So, assuming that I did suck vacuum pump oil into the system, what would be the downside of running it and taking my chances?

Bill

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Bill
1981 380sl

You need to take it apart then unfortunately. The oil won't be compatible with the refrigerant so you'd have to add the regular oil otherwise burn out the compressor. Then you are massively over spec for oil.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Yep! I was afraid of that. What a drag, and all because of a mistake that never should have happened.

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Bill
1981 380sl

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

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Bill
1981 380sl