Cubic Centimeters to Ounces for A/C Compressor

[luckymike]

I'm struggling to find a solid answer on how much oil to add to my new a/c compressor.

-- Manual says 20cm3. That appears to convert to .676 ounces. That seems way too little.

-- A/C shop tells me to add three ounces.

-- Compressor shipped with 2-3 ounces (rough measurement comparing my unmarked catch vessel to a 4oz glass)

-- @LWB250 added four ounces here: OWNER - LWB250 (E420) | Owners and Their Cars

I'm leaning toward just putting the drained oil from the new compressor right back in and calling it good. But what's with the manual asking for .676 ounces?

 

[gsxr]

The FSM is VERY VERY confusing on this topic, IMO. I still have a hard time wrapping my head around what the specs are.

Note that 83-525 says 160 cm3 for "new oil capacity in AC compressor", which is 5.4 oz. I think section 3 where it shows 20 cm3 is meant in addition to whatever amount was drained out, maybe? Also, job 83-530 (C) also says 160 cc / 5.4 oz for a new compressor.

Did you drain the oil from the old compressor and measure the amount? That's what the FSM says to do, although if the system was low on total oil charge, I suppose it's possible the old amount could be low as well?

 

[dionphaneuf]

How did you lose AC @luckymike - did your other compressor grenade itself, or just die more gallantly and then you reclaimed AC for this swap? If it's the latter, I'd do as Dave suggests and transfer oil over to maintain the same balance, perhaps with a touch extra.

If the old compressor grenaded you'll probably want to flush and also replace receiver drier.

 

[luckymike]

@gsxr I did drain the old compressor. It had essentially nothing in it. I am a lot more comfortable with 5.4 ounces then with even three. Thanks for pointing that out in the manual. My AC shop says it’s better to over fill the oil rather than to underfill it.

@dionphaneuf The old compressor began squealing at idle and was basically not used after that until it was removed. Based on the tiny amount of oil that came out of it, I’m going to assume it did a low speed grenade. On the AC shops recommendation, I ran a Q-tip into the two lines that come off the compressor. Not completely clean but not bad enough that I’m going to deal with a flush this time.

I guess my question now has evolved to whether to just dump all of the new oil that came with the compressor back in, or even add to it. Since my AC guy recommends 3 ounces, maybe I will just go with what the compressor came with.

Thank you both. Stay tuned…

 

[gsxr]

Hmmm. If the old compressor was empty... that means the entire system may be low on oil. The FSM has specs for amounts to add when other items are replaced (drier, evap, condenser, piping, etc). I'd guess you should add a bit more but don't go crazy. Too much oil will reduce efficiency (less cooling capacity). You can re-use the oil that came with the new compressor and add fresh stuff to it. Denso ND-8 preferred but any double-end-capped PAG oil should suffice.

 

[LWB250]

The last few systems I've done (W210s) had empty compressors, but they didn't grenade and weren't open, either. Both old and new compressors were essentially empty.

There's an amount for the compressor and for the receiver/dryer. I think on both of the W210s I did the total between the two was around seven ounces, so I added that much to the compressor. It is SUPER critical when you do this that you rotate the compressor by hand a good 10-20 rotations to get the oil into it and evenly distributed around inside the compressor. If you don't, you'll hydrolock the compressor and destroy it.

Be careful while you're adding oil and turning, as if you go too fast you'll get a geyser of oil out of the ports. Turn is slowly and the oil will make it into the cylinders and eventually distribute itself around the compressor. You'll be able to tell when it's well distributed as you turn it, as a few of the cylinders will fill up and make it hard to turn for a turn or two. Once it's distributed around the compressor it will turn smoothly throughout it's rotation. Don't rush this, and do it until the compressor turns easily in a full rotation.

Dan

 

[luckymike]

The last few systems I've done (W210s) had empty compressors, but they didn't grenade and weren't open, either. Both old and new compressors were essentially empty.

There's an amount for the compressor and for the receiver/dryer. I think on both of the W210s I did the total between the two was around seven ounces, so I added that much to the compressor. It is SUPER critical when you do this that you rotate the compressor by hand a good 10-20 rotations to get the oil into it and evenly distributed around inside the compressor. If you don't, you'll hydrolock the compressor and destroy it.

Be careful while you're adding oil and turning, as if you go too fast you'll get a geyser of oil out of the ports. Turn is slowly and the oil will make it into the cylinders and eventually distribute itself around the compressor. You'll be able to tell when it's well distributed as you turn it, as a few of the cylinders will fill up and make it hard to turn for a turn or two. Once it's distributed around the compressor it will turn smoothly throughout it's rotation. Don't rush this, and do it until the compressor turns easily in a full rotation.

Dan

So glad I’ve procrastinated this install. Thanks for this info!

 

[gerryvz]

Here is information that I posted last summer:

HOW-TO: Replacing 500E/E500 A/C Compressor | "HOW-TO" Tutorial Articles

This HOW-TO is focused on replacing the A/C compressor in the V-8-based W124 Mercedes-Benz models. Since the compressor and key components of the A/C system are very similar on other W124 models, most of this HOW-TO should also apply to the inline-six models. The Nippon Denso compressor as...

www.500eboard.co

 

[gerryvz]

I'm struggling to find a solid answer on how much oil to add to my new a/c compressor.

-- Manual says 20cm3. That appears to convert to .676 ounces. That seems way too little.

-- A/C shop tells me to add three ounces.

-- Compressor shipped with 2-3 ounces (rough measurement comparing my unmarked catch vessel to a 4oz glass)

-- @LWB250 added four ounces here: OWNER - LWB250 (E420) | Owners and Their Cars

I'm leaning toward just putting the drained oil from the new compressor right back in and calling it good. But what's with the manual asking for .676 ounces?

I emptied the oil that came in my compressor, and then added slightly over 5.5 ounces of fresh new PAG oil when I did the job last summer.
Note that my compressor came with about 4 oz of oil in it, which IMHO is not quite enough (but probably not enough to grenade the compressor).

As @LWB250 said, SLOWLY rotate the compressor about 8-10 rotations after adding oil. DO NOT rush this with fast rotations, or you WILL get a PAG-bath out the top ports.

If you haven't read the HOW-TO linked above that I did, I recommend you do.

P.S. Pyrex kitchen measuring cups are your friend