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General question how much oil to add with leak

jimdays on Fri May 22, 2015 7:29 AM User is offline

I have a 2001 Ford Focus which I bought used in an emergency. When I bought the car, I noticed (in hot weather) the A/C compressor only engaged for about 10% of the time. I had a professional evacuate and recharge the oil and refrigerant. The mechanic said there was leaks in the system, but I elected to spend no more money for repairs. I also decided not to add any stop leak (although the mechanic wanted to do that). (Stop leak may have been added before I bought the car.) After he recharged the system, the A/C worked fine for a few weeks, then started to cycle off with increasing duration.
So each year I add about 2 cans of refrigerant just before I take an annual summer trip. I have added about 4 cans total since the mechanic evacuated/recharged the system.
My question is: I would like a ballpark answer how many cans total of refrigerant can be added before it is prudent to add a 2 ounce can of oil. Up to this point, I have not added any oil since the mechanic recharged the system. Since I have now added about 4 cans of refrigerant over a several years, I figured it is time to add a 2 ounce can of oil. I know that too much or too little oil can damage the system.

Edited: Fri May 22, 2015 at 7:31 AM by jimdays

mk378 on Fri May 22, 2015 8:43 AM User is offline

Depends on the type of leak. Many leaks only leak out gas and you don't lose any oil while the car is parked (which is almost all the time). When the system is running the oil moves around and a very small amount will come out of any leaks.

Some effort should be made to find the leak. You can buy a can of 134a with UV dye (costs about $1.00 more than a regular can) and use that next time to charge. After running the system, some dyed oil should appear at the leak point. The dye is visible under "blacklight" illumination.

emsvitil on Fri May 22, 2015 9:23 PM User is offlineView users profile

Sounds like my 2002 Focus. I add about 1 can a year, so I'm interested in the answer too.

I'm pretty sure my leak is the evaporator (or the connections to it inside the dash) as I can smell the oil after the car has been sitting awhile. (which is why I've just been adding cans)

Do you have an interior smell the first time you get in the car for the day?


jimdays on Thu May 28, 2015 7:55 AM User is offline

This car was designed as disposable. Before I bought the car, somebody changed the cabin air filter (under the cowl). The cowl clips break off when removed and won't re-install properly. The result is that there was 2 inches of water in the car from rain. So there are always "smells" in the car and I can't say what might be refrigerant. All Focus in those years leaked water if the cabin air filter was replaced.
I just rigged up a simple attachment to charge the A/C with pure propane from 16oz camping containers, then I noticed a banner ad saying that Rural King has refrigerant $3.99/12oz can. I just checked the pressure on the A/C system with motor off at 70 degrees and the pressure was 30psi, meaning all the liquid refrigerant has leaked out. Last time I recharged the system was 10 months ago, so roughly in a year, 24 oz of refrigerant leaks out. No repairs will be done on this car - been there done that.

HECAT on Thu May 28, 2015 8:28 PM User is offline

OK, so the oil migrates with the refrigerant to cool and lubricate the compressor. It is a precise balance of oil and refrigerant to cool and lubricate properly. Every time it is run low on refrigerant the oil flow to the compressor is compromised; just like running the engine with 1/2 of the engine oil. Furthermore, the oil is not miscible with propane as the refrigerant, which means the oil will not properly flow even when fully charged with propane. The system is not designed for a flammable refrigerant, so keep in mind if this is a evap leak; you are putting yourself and others at risk (maybe you do not care). How much oil to add back is a WAG. It requires the guesstimate of how much is lost. If you are constantly recharging a leaking system and not seeking to fix it; just add an ounce or two. Please keep in mind, this is definitely not professional advice; just trying to answer the question. You could add some cooking oil if you want; IMHO, its not going to hurt it any more than you already are.


HECAT: You support the Forum when you consider for your a/c parts.


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