How much oil to add to a/c - PeachParts Mercedes-Benz Forum

vstech · #1 07-11-2015, 08:54 AM

Only way to know how much to add is to remove all oil by flushing out all components, and filling the correct amount. Too much oil is as bad as not enough...

vtmbz · #2 07-11-2015, 09:26 AM

I thought you might say that... The problem is that I have no history so no idea when last oil was added. Besides which, the car was pressure washed before I bought it so no residue.

If someone added an ounce too much, would that ruin the system. I'm thinking adding a small amount might be in order, like maybe an ounce. I know this not how you operate in general; I'd just hate to see my compressor lock up for lack of maintenance. It's obviously throwing oil. A full flush is not called for since the system works, and besides, we hardly use ac here anyway!

Or will the compressor warn me when it's low on oil by squeaking before it locks up?

engatwork · #3 07-11-2015, 11:06 AM

Quote:

squeaking before it locks up?

It will happen all at about the same time.

On my 98 E300 I had a leaking o-ring at the hose coming off the top of the compressor. Replaced the o-ring and added approximately 1-1/2 oz of oil and have not had anymore issues since. I had charged it a couple times and could see the oily residue on the outside of the hose. You can hang meat in the car if you wanted to

.

ROLLGUY · #4 07-11-2015, 11:35 AM

Quote:

Originally Posted by vstech

Only way to know how much to add is to remove all oil by flushing out all components, and filling the correct amount. Too much oil is as bad as not enough...

I have experience with adding too much oil, and it is not good. However, if there is any leak detector dye in the oil that was/is in your system, you should be able to see it with UV glasses and light. If the oil you see by your PS pump is in fact refrigerant oil coming from the compressor, you have a major refrigerant leak as well. Make sure what is leaking and where before assuming you can/should add oil to the system. You could have a small leak in one of the hoses (tiniest pin holes) that leak refrigerant, but not oil (oil molecules larger than refrigerant). That was exactly the problem I had:
I should have known better than to try to bring the GM R4 compressor back to life
Every time refrigerant was added, a little oil was added as well. It was assumed that oil leaked out with the refrigerant, but that was not the case. A cluster of small pinholes was found on the large hose going into the cabin (soapy water), but there was no oil present. The hose was replaced, and more oil added with the refrigerant charge. Don't do what I did and assume you can keep on adding oil each time you add refrigerant! The results can be disastrous!

You also said you are using ES12. I don't know much about these refrigerants or the specific oil they require, but you may have a problem wit oil compatibility as well. Again, it is always best to start from scratch, and flush the system. It also goes without saying, but you should fix any leaks first!