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Old 05-17-2009, 09:19 AM   #1
alpinewhite318i
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Default Add oil before vacuuming out system?

Do you add the compressor oil before you draw a vacuum to the R134a system?
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Old 05-17-2009, 10:11 AM   #2
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nope before you charge it
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Old 05-17-2009, 11:14 AM   #3
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You can't add oil after you vacuum because you'd have to open the system again and then vacuum again. Unless you inject oil by using the type where it's in a can like the refrigerant, where you insert it through the service ports. I don't like that method.

1. Add oil to the compressor. You can spread some of the oil around, putting some in the evaporator and condenser if you want. Sometimes the factory sends new compressors filled completely with required amount of oil. You just hook it up, so I don't think not spreading around the oil is too bad.

2. Pull a vacuum for 5 to 10 minutes. Shut the pump down and look at your gauges to see of the needles are shifting because of a leak. The gauges will move a bit if any moisture in the system is evaporating. This will change pressure. When you're sure there's no leak then continue to vacuum the system for 30 minutes or more. The length of time you need to vacuum depends on outside ambient temperature and how low a pressure your pump can pull. The better the pump or the hotter the air temperature, the less time you have to vacuum.

3. Follow the typical instruction to add refrigerant. Add the specified weight of refrigerant. Count the number of cans and guess the amount remaining in the last can by tipping the can on its side and watch the manifold gauge set peep hole fill with liquid refrigerant. This tells you that the liquid in the can is exiting the can neck. Based on the angle of the can you can guess the amount of refrigerant remaining in the last can. If you aren't using a manifold gauge set with a peep-hole then you can't use this method to guess the refrigerant remaining in the final can. The alternative is to use a postage scale to weigh the cans.

I use a normal can / container of refrigerant oil. I use a medical syringe (the bigger type, sometimes bought at hardware stores) to measure out the oil in cc's or mL's, then squirt it into the system, sometimes spreading it around the system.
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Old 05-17-2009, 11:25 AM   #4
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How many ounces of oil did you add? I am putting in a seiko compressor from a 1991 325I in my car. Also I am going to use ester oil?
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Old 05-17-2009, 01:42 PM   #5
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If you have a vacuum pump, it's just a little extra time to vacuum before and after adding the oil.
Solvents and moisture will mix with the oil and take much longer to evaporate, so it's better doing this way.

Seiko Seiki (BMW-sourced R134a retrofit) uses 220+-20g 7.5oz oil
BMW recommends cleaning the system and using PAG oil.

I'm guessing that you don't have a retrofit label:
64-50-8-363-254 Label for R134a conversion on e30 $3.54/2.81

Last edited by DJB : 05-17-2009 at 01:44 PM.
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Old 06-18-2009, 11:59 PM   #6
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how do you clean the old oil out of the system? can you open up the valves and blow with compressed air?
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Old 06-19-2009, 12:44 AM   #7
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The old books say to fill and empty the system several times with fresh R12, presumably throwing it out each time.

You can get most of the oil out by removing and draining the compressor, and replacing the drier. The rest must be rinsed out of the hoses and coils with a flush.
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Old 06-19-2009, 10:58 AM   #8
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To drain the compressor you will want to remove it from the car. Turn the shaft by hand while getting the oil to drain by hand. On the Bosch-Behr compressor, in its belly, there's a sponge material I believe to probably capture some of the oil from the exhaust to keep it in the compressor body. That thing will be soaked in oil. Turning the compressor by hand won't be getting that oil out. The only way to get that out would be to disassemble the compressor. I would say don't sweat it too much. Just drain as much as you can. If you're converting to R134a then if you're using PAG oil then get double end capped (DEC) type PAG. Otherwise use Ester (POE) oil instead.

Besides the drier/recevier canister, the rest of the oil will likely be in the evaporator. To flush that you'll want to remove the evaporator from the dash. Not that hard to do. You should flush it with a proper AC flush. I've heard of people using brake cleaner, but I wouldn't.
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