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  #1  
Old 08-28-2015, 06:04 PM
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300E A/C Repair, what to do with oil?

I have 2 300Es (one's a 300CE, still M103) that have have AC systems that sound like they are working but just have no refrigerant. They are still using R12 fittings. As far as I know, they have not been charged for over 10 years, both vehicles.

My question is, what should I do with the oil that is in the system? I don't even know what is in there, so should I just dump it all out/flush the system with one of these kits:

http://www.amazon.com/FJC-2710-System-Flush-Kit/dp/B0002JMEQW/ref=sr_1_1?ie=UTF8&qid=1440799964&sr=8-1&keywords=ac+flush

If I flush it out, what should I replace it with? Does it depend on what refrigerant I am going to use or does it depend more on the compressor I am using? I am reading a mix of ester oil, PAG, and mineral oil when I am going through posts from this forum regarding A/C oil.

Or is it alright for me to assume the oil is fine since the compressor hasn't seized or anything and just vacuum/charge it with refrigerant?
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Old 08-28-2015, 08:51 PM
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Check for leaks first.
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Old 08-28-2015, 10:12 PM
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Ester oil gives you the option of going with r12 or r134. It seems like a no brainer
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Old 08-28-2015, 10:32 PM
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My experience with a couple of old A/C systems that I was converting, is that they both had no obvious oil in the compressor or the drier. They were still working so there must have been some oil circulating with the refrigerant but most had either leaked out with the refrigerant leaks over the years or had gone with the drier changes that were made over the years. The oil to be added depends on what refrigerant you plan to use. I converted to 134a but that was because I ran out of R-12. If you have a source of R-12 at an affordable price, I would go with that and use an oil that is compatable with what might be in your system.
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Old 08-28-2015, 11:44 PM
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Quote:
Originally Posted by lorainfurniture View Post
Ester oil gives you the option of going with r12 or r134. It seems like a no brainer
Thanks for confirming. I did a Google search for Ester vs Mineral vs PAG and came across this link: Oil used In Automotive Air Conditioners

I guess I'll be using ester oil just to be compatible with either.

Another question, besides running an AC flush through the lines, is there anything I need to do with the compressor? Is there some sort of drain plug to dump out the old oil from or is just flushing/vacuuming the lines sufficient?
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Old 08-29-2015, 12:48 PM
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John, my advice would be to do an overhaul while the system is empty. Replace the o rings, replace the receiver drier, and replace the expansion valve. When you have everything apart you can clean up the condenser and check for bent fins. At this time you can either choose to remove the compressor and empty out the oil or you can button everything back up once the system has been overhauled and flush everything out and add the new oil.
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Old 08-29-2015, 07:12 PM
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Quote:
Originally Posted by lsmalley View Post
John, my advice would be to do an overhaul while the system is empty. Replace the o rings, replace the receiver drier, and replace the expansion valve. When you have everything apart you can clean up the condenser and check for bent fins. At this time you can either choose to remove the compressor and empty out the oil or you can button everything back up once the system has been overhauled and flush everything out and add the new oil.
How do you remove oil from the compressor? Remove it from the car, tip it over, and dump it out of one of the ports where the hoses bolt up to?
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Old 08-30-2015, 02:04 AM
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Yes. That's what I did not too long ago. Maybe a month or 2 ago.
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Old 08-31-2015, 11:58 AM
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Originally Posted by tyl604 View Post
Check for leaks first.
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  #10  
Old 09-07-2015, 11:43 AM
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But be sure you have oil back in the system or you will fry your compressor. Ask me how I know this!
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  #11  
Old 09-11-2015, 09:26 AM
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Hey I'm a HVAC mechanic and I would def recommend replacing the oil and leak testing if it hasn't been working for that long.
Oil in these systems absorbs moisture from the air and wrecks it. Also the oil helps keep the system sealed to prevent further leaks such as on the rubber seals on the shaft etc. so I would be replacing all the seals too which would have dried out and cracked - unless you want to be putting gas in the thing every year.
You should also run the air con at least every week or two to get the gas and oil circulating to stop the seals from drying out and cracking/leaking.

All that said, I have not done much work on car AC systems this is just what i have picked up from talking to my work mates etc over the last 10 years
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Old 09-11-2015, 12:27 PM
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Quote:
Originally Posted by psy3825 View Post
Oil in these systems absorbs moisture from the air and wrecks it.
Curious how oil in a pressurized system comes in contact with air? Sounds like what happens to brake fluid (in the reservoir).
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Old 09-13-2015, 02:04 AM
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Thanks for all the tips, I have just started to purchase what I need to service my AC. As for adding oil back into the system, what's the recommended method for this car?

Do I pour 8 oz oil from a bottle into different places like condensor, compressor, and drier? Or should I use a charge can that is pressurized and charge 8 oz oil into a vacuum ac system?

Last edited by John5788; 09-13-2015 at 02:30 AM.
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