What Is 1991 W126 350SDL Compressor Oil Capacity - PeachParts Mercedes-Benz Forum

Squiggle Dog · #1 08-24-2016, 09:53 PM

I completely refurbished the air conditioning system in a 1991 W126 350SDL. Now it is going to go in to a shop to have it charged. But I do not know how much compressor oil goes in. The system was completely flushed and a new compressor is installed (but was drained of oil first).

I am getting conflicting information. Here Refrigerant and oil capacity charts - M to P || TechChoice Parts says it takes 7.75 oz (229.19 cc).

I looked through the W126 service manual on CD and it does not show the Denso compressor, just the older Delcos for older models. It specifies 300 cc (10.14 oz) for the gasoline engines, and 170 cc (5.75 oz) for the OM617, which is a different engine from the OM603 this car has. I would assume this information does not apply because they are different engines and compressors.

But, I did find a section in the 1986 supplement that shows a Denso compressor like in this car. It states the total oil capacity is 120cc (4.06 oz). This is very different from the 7.75 oz that the link above shows for a 1991 350SDL. I also don't see to which model the 1986 supplement is referring.

Another observation is that in the link above, in some cases it shows two identical models of the same year (1992, a changeover year), and the only difference is one uses R12, and one uses R134a, therefore they use different oils. I noticed that the ones that use R12 mineral oil almost all use 7.75 oz, whereas the ones using R134a PAG46 oil use 8.5 oz. It seems everything else is the same, so does one need to use more PAG oil than mineral oil when converting to R12?

I am so confused. Is the total refrigerant oil capacity 7.75 oz or 4.06 oz, or 8.5 oz since I plan to use PAG46 since it will be getting R134a? It's going in for a charge tomorrow and I don't know if the air conditioning shop will know, or if they will just guess at it.

compu_85 · #2 08-24-2016, 10:03 PM

The 1991 car has the 17cc compressor as opposed to the 1987's 15cc.

Doesn't your car have a sticker on the core support showing the oil capacity?

-J

Squiggle Dog · #3 08-24-2016, 10:09 PM

Thanks for the response! Nope, no oil capacity shown. Just refrigerant weight.

So, I guess that may explain the 4 oz shown for the 1986 supplement versus the 7.75 oz shown in the link. I better make sure my roommate ordered a compressor for a 1991 350SDL instead of one for a 1987 300D, because that's what the engine is from.

Squiggle Dog · #4 08-24-2016, 10:31 PM

The compressor is a Denso 10A17C, so it appears to be the 17cc model. It looks correct versus the smaller-looking ones for a W124 300D.

Squiggle Dog · #5 08-25-2016, 08:25 AM

It just surprises me that the volume of oil nearly doubles between a 15cc and 17cc compressor!

Squiggle Dog · #6 08-25-2016, 09:51 PM

Well, it's all charged now. But it does not feel cold. Just lukewarm. Disappointing. I guess it blows 48 degrees at the vents, but it sure doesn't seem that cold.

funola · #7 08-25-2016, 10:04 PM

Sorry to hear that. I just finished mine and having better luck, so far anyway.
But it's a R4 and legend has it that it could blow up anyday.
R12 vent temp 85 300D 38.5F @ 87F ambient

compu_85 · #8 08-25-2016, 11:11 PM

It should be better than that I'd think. Do the condenser fans come on? Is the sight glass foamy?

-J

funola · #9 08-26-2016, 02:04 PM

Was system pressure tested for leaks before evac/ charge? Was it charged from cans or from 30 lb tank by weight? What were the manifold gauge pressures?

Squiggle Dog · #10 08-26-2016, 03:01 PM

The condenser fans come on. The sight glass looks clear. At first it looks a little whitish but then it clears out within a few seconds.

I don't really know any details about when it was charged except the vent temperature was 48 degrees. My roommate drove it to the air conditioning shop while I was at work.

It may be that the controls or flaps may not be working correctly. Or that the monovalve is letting in warm coolant. It seems like the project that never ends. I really want to get started on my car.

funola · #11 08-26-2016, 03:20 PM

Did you do a pressure test before bringing the car to the shop? Easy to see if the heater is letting warm air in, just feel the heater hoses in/out the firewall. If the hoses are cool, no heat is getting into the cabin.

My Behr made in China receiver dryer which I bought approx 5 years ago does not even have a sight glass.

compu_85 · #12 08-26-2016, 06:38 PM

If the sight glass goes clear the charge is probably close. Is the suction line at the compressor cold?

-J

Squiggle Dog · #13 08-28-2016, 02:37 AM

All is well! I found that even though I couldn't find a vacuum leak, the vent pods weren't opening and letting any cool air get through the vents; however the floor vents were stuck open with some metal that someone propped in there.

So for now I teed the vent pods to the main vacuum source going to the switchover valve and removed the home-made floor vent props.

Now it blows nice and cold and strong through the vents instead of an anemic lukewarm breeze.