GM & Aftermarket A/C Compressors vs MB compressors
 

Some time ago, the following was posted on alt.auto.mercedes. Can anyone confirm or provide a link to a manufacturer's site that confirms the difference in lube oilhole between GM and MB compressors?

"A word of advice on buying a replacement compressor:
Any one you get that does NOT come from Mercedes will have the front bearing
cover installed UPSIDE DOWN. Look at the cover on the front behind the
clutch. It will have 4 bolts. Between 2 of the bolts will be an embossed X.
This is the position of the oil hole to lube the front bearing. The R4
compressor was originally designed for GM cars with the compressor mounted
on top of the engine. The X and the inlet/outlet port is UP. Mercedes used
the compressor but rotated it 180 degrees and mounted it under the engine.
This put the ports DOWN. Then they rotated the front cover so the X is UP.
Oil does NOT flow uphill. If you use an aftermarket compressor with the X
down, you will starve the front bearing of oil. It may last a week, a month,
6 months.... depends on the quality of the bearing they put in. "

Here is link to Google Groups:

http://groups.google.ca/group/alt.auto.mercedes/browse_thread/thread/8db733da96f6ae79/6f27b1d537b97996?q=mercedes+air+compressor+oil+upside+down&rnum=4&hl=en#6f27b1d537b97996

Bull *~!?

I have installed at least 50 R4's that didn't come from MB on MB's & never have seen a premature failure!

Here is a good example of that MB crap! The A6 compressor from a MB dealer lists for $2,370!!!! I buy that exact compressor from a GM Delco supplier brand new for $305!! & that includes the clutch. Does MB really need to make $2,000 profit on a single compressor?????

Whoever wrote that probably meant mounted low or mounted high.

Questions still comes down to whether or not the compressor end caps are rotated on MB,s for proper lubrication.

This story keeps coming up on the net and I am just trying to get a definitive answer.

The GM A6 has a "sump" and must be mounted sump down, the R4 doesn't have a sump!

I just took the yoke off the front of a GM AC Delco R-4 that I had sitting around. It was NOS for a 90's Chevy Suburban (I think....pretty sure).

Despite what I thought :shocked3: (and what some have said on some of the other MB mailing lists and forums), there WAS an "X" and TWO oil journals on the inside; one to the front needle bearing and one to the shaft seal.

The journals point to the center (obviously), so mounting this R-4 with the "X" up would seem to be wise; gravity being what it is and all.

I have taken apart several other R-4's and never noticed this before. The yoke on this R-4 was the smaller version (there are two models of R-4's; lightweight and regular).

Thanks for checking this jbaj007 - First report that the "X" is actually there and that it can make a difference!

Compressor comments...
 

Hi there,
For what it's worth, the A4 compressor on my Astrovan is mounted on "top" of the engine. It's actually mounted on the accessory mounting plate, which bolts to the front of the heads and block, but is above the block itself. I believe the one on my S15 pickup is the same. Interesting advice, probably a good thing to keep in mind. An AC guy I trust says to use Sankyo compressors as they last longer than the A4 compressors. I don't know from personal experience, though... the A4 compressors on my rigs all work ok, just are noisy in hot weather.

Regards,
Richard Wooldridge

Now I'm confused. :confused: I have heard the same story about not using an R-4 designed for a GM product for the reason pointed out. MB Doc, you stated that you have installed at least 50 R-4s that did not come from MB, but you were not clear as to if these compressors came from aftermarket sources but were still intended to be installed on MBs and not GMs. Please clarify.

Thanks,
Peter

It's true!
 

Hello all,
I just checked in the factory manual for my 1985 S15 pickup truck, and in the R4 overhaul section it does rather clearly state in the R-4 compressor front head and/or O-ring section page 1D1-18, (REPLACE, Par 3) "Position the oil hole in the Front Head to be "UP" when assembled to the compressor cylinder to correspond with the "UP" position of the compressor. Install the Front Head and tighten the front head mounting screws to 27 N'm (20 lb. ft.) torque."
There is also a picture that shows the oil hole. The front bearing is a needle bearing, and the front head is held on with 4 screws. Seems to me that it would be a simple thing to rotate the front head to the desired position before installing the compressor, it might be a good idea to use a new o-ring. The only problem is that one would have to pull the clutch and clutch coil off the front head to get to the screws.
So here's the dilemma- the oil hole really doesn't have any oil collection surface, so does it really matter if it's up or down? If it's down, the oil will enter the bearing area along the shaft surface and leave from the hole, if it's up the oil will enter through the hole and exit from the shaft surface. There's not really that much difference in my opinion. But, it appears the information given is correct.
Regards,
Richard Wooldridge

You get the idea, even with quicky photos.

well cadelac put the compressor on top of the eng. in the 70"s in front of the carb. even the log fregadair unit,was on top.also oldsmobile.

Well today my comperssor siezed so I will be removing it and installing the old one I had. The new (not rebuilt) one was from ACKITS.com It has lasted 1.5 years. The old one was installed by Mercedes at ******** in the DFW area. I will compare the 2 and let you know.

Dave

Dave

What did you find?

I just had a new R4 fail during charging and somebody reminded me of this thread.

Failure during charging is usually:

1) Just a bad compressor sneaked thru QC.

2) slugged by charging refrigerant as a liquid and the reed valves popped.

3) debris from previous compressor failure hit the new one.

What about substituting the R-4 with a Sanden, Sankyo or Denso etc compressor . Any suitable models of these for my 300SD (compressor locked up ) ? - Thanks

I wonder if you or someone else can talk about the compressor on my 1984 300 SD. The name plate identifies it as a " Harrison -Mod# 320". Is this 'lightweight' or 'regular', or what? I makes a lot of noise, so I disconnected the belt - I think it needs only a new or remanufactured clutch. But where to get one - that is the question! :confused:

Padraig

I wonder which GM and NAPA part#s are the $100 R-4 compressors Diesel Giant gets from NAPA ?

This is a quality rebuild R4, but, personally I'd look for new. The R4 is not known as a really "robust" design in the MVAC community.

http://www.ackits.com/merchant2/merchant.mvc?Screen=PROD&Store_Code=AMA&Product_Code=000113CP


Here's new: http://www.ackits.com/merchant2/merchant.mvc?Screen=PROD&Store_Code=AMA&Product_Code=15-20206

changeover kits for older MBs
 

Apologies if this topic has been addressed already...down here in MD it is getting hot. I have three vintage MBs that I would like to update the AC in...a 6.3, a 280SL, and a 3.5 cabriolet. Does anyone know a source for rotary compressors and mounting brackets for these cars? I have a friend with an auto AC shop that can help with the changeover, new driers, etc, but I would like to find a source for the parts.

Also, does anyone have an opinion as to whether the systems should be changed to R134 or left with R12 in them?

Thanks in advance.

Jim, I don't understand why you want to change from bullet proof compresors to the higher failure rate newer style compressors. The A6 on your 3.5 is about the most durable compressor you can get. The only reason car mfgs quit using them is, because they weigh as much as a small Japanese engine. The York compressor on your 280SL is also an excellent compressor. I would buy a new one and not rebuilt. If you get a rebuilt from say Sedona or Phoenix, the metal in the rods and pistons is pretty well fatigued. I can't remember what's in the 6.3, but I think it's a York. I'd also stick with R-12.

compressor issues
I have been purchasing compressors from the local a/c supply house. They do have the x and it is in the wrong place for the MB application. One of the compressors lasted about 1.5 years.
My question is is it just a matter of removing the four front bolts and rotating the front to the correct position?

Essentially yes. I've always had the clutch off, to clear the hex head screws.

Also with the "X" down, the oil to the shaft seal (a NOTORIOUS source of R4 refrigeranr leaks) is obviously less; so overall, it's worth putting the "X" up..

I went to the a/c shop where I purchase the compressors today and looked at every compressor they had listed for the '81 300D. There were three different p/n compressors that they had that would work. All were brand new Delphi compressors and none of them had the x where it would be in the "up" position in the w123 once it is installed. I have ordered one that is supposedly only for the MB and will report back on what I see. The guy that runs the shop adjacent to the supply house (a very big and very busy a/c repair shop) said it did not matter where the x is when these things are mounted.

one less thing to worry about
 

I called Delphi customer service today and talked with a 30+ year verteran. He pulled their documentation on the r4 unit and they "recommend" installing it with the x in the up position but on the same hand he said it does not matter. The oil is splashing around in there so much that the front bearing is going to get some lube on it no matter where the x is. He stated that in working there for 30 years that this was the first time anyone has ever asked this question and that they have a MB trained tech on staff and he reiterated the same thing - that it should not make any difference in the life of the compressor. I will be replacing a one year old new "locked up" compressor this coming weekend and hopefully will be able to take the old compressor apart to determine it's failure mode.

Has anyone substituted for an R4
 

Look at the compressor on a euro W123. They are a different type. Unfortunately, the last euro 123 that I saw I was unable to tell what compressor it was. The brackets were pretty straight forward and the car had been converted to 134. I don't know how well the system worked.

i've been replacing r4's for thirty years and only now
'am i being made aware of this oil passage issue.
r4's are not a bad compressor. originals lasted
years and years. some over ten years.
its the shoddy repair and use of rebuilts that
messes things up. plus not adding oil when servicing them.
if one comes apart then you got something i refer to as
black death. almost everything needs
to be replaced. the evaporator can stay as its single
row and can be flushed. condenser is double row and needs
to be replaced. after everything is done you MUST
install a filter on the suction line just before the comp inlet.
or do the job again.
the r4 comp was designed to be lubed by the oil in
the freon so i'm just not sure that the x is a real issue.
won't hurt though. i'm gonna see if i have a genuine
mb one around and check.

george

george has more experience with MB than Daimler, himself; so I listen.

I'm not so sure, though, a genuine MB R4 (even though made by someone else) would need an "X" to identify which is up since they would be identified for one specific use already by MB. It's the AC Delco, Harrison, Delphi models (aftermarket OEM) that would need it since they are used in many different applications, both high and low mount, for different auto makers' marques. On the MB unit the channel/"hole" may well be there, just no identifying mark, since they already know which way it's going to be used because of the manifold port position and the specs on the box.

The lubricant is in the gas so the compressor gets its share, maybe even the front bearing gets enough, but...... the A6, R4 H6 incarnation series has undergone many shaft seal issues over the years. Steel/steel, ceramic/steel, caged/uncaged, single lipped, double lipped, heck, even triple lipped. The admonition to run the A/C once a month to "lube the shaft seal". All of this points to, at least an issue, with lube to the shaft seal which they apparantly tried to address with the extra "port" to the seal area. The oil mist would "stick" to the solid surface and tend to go downhill to the seal. I wouldn't tear a system apart to check it, but if given the choice (and mine had an "X" (my old ones didn't, I'm pretty sure, now)), I'd go "X" up, on a new install.

This is really interesting! I have a generic question for the AC experts. Is there anything that one can do to prevent premature compressor failure? And what about the "black death" failure, how do you prevent it?

Hi George, Yes the R4 - the 'workhorse' compressor of its time was designed for efficiency, but not for durability.

The R4 on my 84 300SD (Harrison #320) might even be the original one, but I don't know. Anyway, it recently started to make great noise 'though still cooling (not squealing type noise ) whether the AC was engaged or shut off. I suspect that the prob. is a the clutch. Question : Can one replace the clutch without benching the compressor?

I take note of your recomendation in replacing a compressor (highlighted above) to replace the Condenser and install a filter in the suction line. Why would one replace a condenser if it weren't leaking, and what type of filter would one install - are you referring to the Dryer, perhaps?

Finally, George, how does one indentify a 'genuine MB compressor"?

The one that came back after a year had a locked up clutch. The compressor would still turn fine. In addition, the compressor with the locked up clutch did not even have an "x" on it.

How difficult is it to reconfigure the GM style compressor for the Mercedes so that the X will be in the proper postion . I assume you at have to remove the clutch but do you have to remove the front seals to rotate the front cover 180 degrees ? It seem like a much less costly option if this job is easy to do since the GM style are plentiful and I have seen NOS prices are under $100 .

Also I tried to loosen clutch retaining nut on my dead R4 Harrison 327 compressor with a number of different brands of sockets . I could not get the sockets to fit because it seems their walls were too thick . What size is the nut What tool works here ? I will then use the Autozone loaner clutch puller to get the thing off so I further disassemble the compressor to see how it is put togther .

- Thanks

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