R4 compressor for 300D - PeachParts Mercedes-Benz Forum

ah-kay · #1 04-03-2012, 07:01 PM

Can I put a R4 compressor spec'ed for GM car into a 300D? Would it be a direct fit with same pulley and belt length? I come across a NOS cheap one. I am planning on changing out the compressor as it is making strange noise. It is a 1 groove pulley.

wildest · #2 04-03-2012, 08:09 PM

But there are some nuances to, like the front seal might not be clocked the right way, which probably won't matter, and you need to make sure all the mount holes are used to keep the middle seal squished properly, and then there are the seals for the hose flange, which will be: o-rings, or solid seals of the same height, or solid seals of different height, and they are color coded. The 2 I've done had the solid seals which were easy enough to sort out, the compressors were GM sourced/cheap scores. Make sure the electrical connector matches. The R4's were in millions of cars for a long time.

engatwork · #3 04-03-2012, 08:26 PM

What year/model 300D? The W123 cars (from 1981 to 1985 IIRC) came with R4's (with oil ports set up for the configuration).

NoSparkNeeded · #4 04-03-2012, 08:27 PM

If we all had a choice of "the best longest lasting compressor", would it be better than one of the brand new R4s, if you had the skills to adapt it? The R4 seems to have a quite limited life, based on what I read. All you A/C guys, what is the most reliable compressor you see?

shadetree77 · #5 04-03-2012, 08:49 PM

the regular GM R4 compressor is mounted diffrently than the MB R4 compressor; the oil sump will be upside down if you try to use a GM R4 compressor and will destroy the compressor in short order...i've heard this many years ago so i'm not 100% sure if that's correct; maybe someone else can chime in and confirm.....

ah-kay · #6 04-03-2012, 08:50 PM

Quote:

Originally Posted by engatwork

What year/model 300D? The W123 cars (from 1981 to 1985 IIRC) came with R4's.

It is a 83 300D as per my signature. R4 compressor are in many GM cars but some installed with multi-grooves pulley. The NOS one I am looking at is a 1 groove pulley, similar to Mercedes. It seems sellers put a premium on anything Mercedes so I try to second source the compressor if they match. I do not care 'most reliable' brand, 'best' brand as they do not exist, so to speak. I just want a 'best fit' with reasonable money.

engatwork · #7 04-03-2012, 08:54 PM

Shouldn't be any problem at all. Is the mounting bracket already there?

ah-kay · #8 04-03-2012, 09:00 PM

There is no mounting bracket. It is just the 'round' R4 compressor and I hope all the mounting holes are the same. I plan to re-use the old bracket.

Yak · #9 04-03-2012, 09:10 PM

The compressor itself should fit. The pulley might be a question mark, but if your old clutch and pulley are okay, there's no reason you can't swap them. The wiring location for the clutch may be an issue in any case. Tools for removing the pulley and clutch are available as loaners through O'Reilly's and/or Autozone. Both Funola and I had threads about the R4 from maybe two years or so ago. He disassembled and took photos, so there's good info there. There should be a DIY on my swap in the Wiki.

The threads have links and sources for some info like the proper size and shape O-ring (if the NOS uses those) since it's not a circular cross section, IIRC. Or the proper sealing washers if the NOS uses those (there are different heights).

I though I paid about $200 for a brand new made in USA R4. CompressorWorks.

Yes the location of the oil "sump" is upside down from the OE version, but you 'could' rotate that if you so chose by removing the front cover. The manufacturer of the new ones says there is no "sump" in his due to the seal design. X does mark the spot. I'm not entirely sold on the theory of the sump while in use, but I do understand the theory for the initial fill regarding improving lubrication. The sump may/may not actually affect lifespan.

ah-kay · #10 04-03-2012, 09:17 PM

Thanks Yak.

I think my concern is the pulley. If I need to swap it then I ain't going to buy a GM spec'ed R4. It is too much hassle and is not worth the saving. I am not in a hurry to change it out. I just want to make sure I have a cheap one sitting around when I want to do the job. I will look again.

Yak · #11 04-03-2012, 09:57 PM

The clutch and the pulley are a combo deal. It's not really that big a deal to pull it with the correct loaner tools. I rechecked the thread. A new CompressorWorks R4 with MB clutch/pulley was $189. That's supposed to be a Made in Dallas, USA part, lifetime guarantee (when used with R-134a).

Funola's thread: interesting pics, links and discussion - dissembling R4 compressor

My DIY thread: crappy pics, lots o' words. Installing a CompressorWorks R4 into a W123

vstech · #12 04-03-2012, 11:10 PM

the one groove gm R4 fits perfectly, belt fits perfectly, but as mentioned the X for the oil bleed hole is on top instead of the bottom when mounted in the MB bracket. BE SURE YOU KEEP THE 4TH BOLT, As GM compressors bolt through, and MB bolts from the back with only three bolts. so a 4th bolt is REQUIRED to fill the fourth hole from the FRONT to the rear to keep the compressor from erupting under load...