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Old 07-25-2008, 06:11 PM
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Join Date: Apr 2006
Location: Birmingham, AL
Posts: 526
Homemade AC vacuum pump

I just bought an old working small freezer in a yard sale for $25 dollars and the reason I bought it was, I'm thinking of pulling out its motor/compressor and make me an AC vacuum pump out of it.

Question: How do I plumb it so that it will still hold it oil and at the same time pull vacuum at the low side/inlet port without losing its oil? I know that those real "dieselheads", are smart and innovative to help me with this experimental project. I think somebody in here has already done this but I can't find him in the Search tab.

The homemade pump that I used to have was a Sanden AC compressor out of a Nissan and have the clutch permanently riveted to the pulley and belted to a 1/2 HP Dayton motor but the compressor seized and also burned the motor. It used to work great and pulls @ least +/-28mmHg before it seized 2 years ago. I can't find a compressor that will fit the bracket that I welded, so right now it's in the scrap metal heaven already.

At least, with this freezer compressor, it's just one piece, and no bracket fabrication necessary. Thanks in advance!
'85 300D Turbo - CA Version
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Old 07-25-2008, 09:20 PM
oldiesel's Avatar
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Join Date: May 2007
Location: florida
Posts: 677
No worries about loosing the oil,just solder a 1/4" male flare fitting on the suction tube and carefully bend the other so it is pointing up at least as high as the top of the unit and fasten some cloth over the open end.I have used one of these for several years on both R-12 & 134 systems on my cars and the engine driven freezer/fridge on my boat.It will pull a vacuum as far down as my gauges go,plenty good enough for any small systems.While you are at it check out this,a friend of mine is a HVAC expert looked it over and says it looks great to him,he is is going to switch my MB to this stuff. Don
Red Green "This is only temporary,Unless it works!"

97 E300D 157000 miles
87 300TD ?141k? miles
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Old 07-25-2008, 09:26 PM
300SD81's Avatar
1981 Mercedes-Benz 300SD
Join Date: Aug 2006
Location: University of Georgia
Posts: 1,080
If you have an autozone around, just rent the vacuum pump from them, you have to leave a deposit, but the rental is free. If you have a credit card that gives cash back, you actually make money
Ich liebe meine Autos!

1991 Mercedes-Benz 560SEL | Megasquirt MS3-Pro | 722.6 transmission w/ AMG paddles | Feind Motorsports Sway Bar | Stinger VIP Radar | AntiLaser Priority | PLX Wideband O2 | 150A Alternator | Cat Delete
1981 Mercedes-Benz 300SD | Blown engine, rebuilding someday...
1981 Mercedes-Benz 300SD | Rear ended, retired in garage.
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