I'm about ready to reconvert from R-134 back to R-12 and purchased a new Denso compressor that already has oil installed compatable to the R-134. What's the best way to remove that oil from the unit and replace with mineral oil compatable with R-12? AC flush? Run mineral oil through compressor over and over till flush? What do you guys do when flushing compressors?

Also had a follow up question. After a complete flush of the AC system, when replacing the oil, do you place it all in the compressor or split it up at various locations along inside hoses while reassembling system?

Thanks!

Herb

The 87 126 should be an OM603 engine. In that case you have a Denso compressor.

That compressor has a sump drain bolt on top near the pulley. It is close to the electrical connector. Be sure to remove that bolt and turn it upside down over a pan. Gently rotate the hub to help push the oil out. I would plan on flushing several oil charges worth through the compressor to get the old oil out. One of the other AC guys on here should know if you can/should solvent flush the compressor.

As for distributing the oil charge, the FSM says you should.
This is for a 124 of the same era the 126 should be similar.

http://w124-zone.com/downloads/MB%20CD/W124/w124CD1/Program/Climate/83-525.pdf

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Hello Jay Bob. I've looked for the sump drain bolt. I can't find it. I'm uploading a picture to see if you can point me in the right direction. Thanks.

Attached Thumbnails

 

Stand it vertical and let it drain. Turn the clutch and it will drain out. Fill your desired oil in the suction side, crank over until oozes out discharge side. Drain again. I did this three or four times on the last Denso unit I installed on the 560... still works fine.

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Maybe yours does not have a drain bolt. The later ones used on the W210 do. Might have something to do with the fact that the W210 style compressors are variable displacement type and so cannot be simply drained out the ports.

The text in the FSM I linked just references turning the compressor upside down and rotating to drain out the oil.

I would try taking off the closure plates over the ports, turn it over a pan, and give it a gentle spin to see what happens. Since this is a fixed displacement type compressor, it may well drain out all its oil simply by being inverted.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Jay Bob. After reading the link you sent I'm still not clear about the distribution of the oil. The link talks about specific component replacement and how much oil to add following a component replacement.

I've determined that my system holds 7.75 ounces. Once I drain the oil out of the brand new compressor, measure and that replace the same amount with mineral oil, do I replace the remainder of the 7.75 ounces into the dryer or other location along the pressure lines to distribute the oil?

thanks

Herb

I just converted back to R12 and very happy with 38 F vent temps R12 vent temp 85 300D 38.5F @ 87F ambient

If your system is totally flushed and dry, put half the oil in the compressor and half in the new receiver dryer. Never flush the compressor with AC flush agent (same reason you don't flush ball bearings- makes them dry) , always use compressor oil to flush compressor. If you have a new compressor with the wrong oil in it, you don't have to flush if you replace the oil with an oil that is compatible with the old oil. Just drain as much out as you can and put the new oil in. It never hurts to flush with the new oil even though it is compatible to the old oil. Since there's always extra in the bottle, why not use it to flush some of the old oil out? I used PAO 68 oil with dye and the bottle was 16 oz. I used 8 oz of it to flush the compressor by capturing it in a funnel filter (funnel with 3 sheets of paper towel) and cycle that through the compressor about 5 times. The filter allows you to see if any debris came out and prevents debris going back in and saves on oil. PAO 68 http://www.behrhellaservice.com/behr-hella-service/assets/media/1065_KlimaKompressoroel_BHS_EN.pdf is compatible with most other oils, has higher temp ratings and non-hygroscopic.

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Don't I have to flush out the entire system of the old PAG oil because of its incompatability with R-12? Even though the PAO 68 appears to be compatable with all oils, what about the old residual PAG oil compatability with R-12?

The compressor, TXV and dryer are the components you should not flush. The dryer and TXV are restrictive and will impede the flushing process. Reason to not flush compressor already given. Everything else should be flushed to remove the old oil completely, that is the only way possible so you can put in the correct amount of new oil. Whatever flush agent you use, you must make sure you get every bit of it out.

I used my own unconventional flush method. A solenoid pump cycling flush agents through a funnel filter (mineral spirit/carburettor cleaner mix, then mineral spirit, then Purple power/ water mix, then plain water) through the condenser, evaporator and all hoses. In my case, I had to make sure no water remained since that is the last flush agent used. I probably ran 8 gallons of water through the system. The original non barrier hoses only saw Purple power and water because the carb cleaner will attack the rubber.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I'm installing a new compressor, new expansion valve and new dryer. My plan is when all the old compressor, expansion valve and dryer are removed, that's when I plan on flushing the entire system.

It appears from what you said that I can just flush mineral oil (I have that on hand right now) through the new compressor to make sure all the old pag oil is removed.

Yes.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

the compressor on your engine is drained and filled from the discharge and suction ports themselves.

The one jay_bob is mentioning is the variable stroke compressor found on later models (W140, W210 etc)

invert the unit and put a cup under it to collect the oil. fill up and rotate compressor by hand and drain it (do this twice to flush out)

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