How should I add the oil to a new R4 comp. - PeachParts Mercedes-Benz Forum

jaybutter · #1 03-29-2013, 11:53 AM

I am replacing my R4 style A/C compressor this weekend. The job seems straight forward after reading a bunch of posts with one exception. How and when should I add the oil charge to the compressor so that it doesn't all run out during the installation? The compressor has stickers that state it was shipped dry. Should it be added after it is install through the gauge port on the suction line maybe? Please advise the best method!

fdanielson · #2 03-29-2013, 12:50 PM

I am assuming you are talking about a diesel W123. For the oil that you add to the compressor you can pour the oil in at the fitting of the low pressure line that comes straight up by the power steering pump before you connect the line that goes across the front of the motor on top. I pour some in, reach down and turn the compressor by hand, pour, turn, etc.

If that doesn't make sense I'll have to take a picture.

eatont9999 · #3 03-29-2013, 11:32 PM

Most the compressors I install go through a similar procedure. I Add an ounce or so of oil to the suction side and manually rotate the compressor shaft to introduce that oil into the compressor for initial start up. On an W123 or W126, some of that oil may spill out during install and that is fine. I always add the recommended amount of oil after the compressor is installed. I add the oil into one of the lines before buttoning the system up AND before vacuuming it down. Suction or discharge line does not matter where you put the oil since you primed the compressor already. I usually do 50/50 in each line so not to bog down the compressor with a bunch of oil.

I hope you are going with mineral oil and R12. No sense in rebuilding an A/C system that was meant for R12 and expecting R12 results with R134a.

jaybutter · #4 03-31-2013, 06:46 AM

Thanks for the great responses! I should have said that this was for my W123 300CD, sorry. In this case the PO had already done a conversion to 134a so I decided to stay with it. Adding the oil to the suction line worked out very well! The A/C performance was actually very good, and that, with Savannah's typical 95F, 95RH summer afternoons! I did buy a new compressor, not rebuilt, that was designed for 134a by Behr, so we will see how it goes.

Now for the bad news! When I was loosening the power steering pump mounting bolts in order to take the belt off, I unknowingly broke the small oil line that supplies engine oil to the injection pump. it is about 1/4" in diameter and about 9" long. Mine was very brittle, I would say original, and with 300,000 plus miles, it has a lot of heat exposure.

So, I am adding the 134a to the system, studying the gauge set, while the engine is silently pumping oil out onto the floor. I almost s*&t my pants when I found that I was standing in a growing puddle of engine oil! The line is part number 6171800127, about $15 from MB and the sealing washers are 007603008109, about $0.25 each. Arrrrrggggg

That oil line, as brittle as it was could have been an engine destroyer! Please check the condition of yours! I think that if it broke while driving that you would have 30-60 seconds before all the oil was on the roadway and your engine seized.