Ok, 1981 300SD...Here in PHX it's a necessity to have the a/c working, and I've had a new compressor installed, new receiver-drier, the system vacuumed, cleaned, vacuumed again, and charged twice! (including two new compressors!!). After about 2 days the compressor starts clattering and clanging like I threw 2 rods through the engine! It still cools well, but at an idle it sounds so bad people look at me scared when I park next to them! Belts tight, bolts tight. Who knows what's happening? Like I said, this happened twice in a row. I might add that I'm set up on 134a, and a Nippondenso (I guess) compressor. Is there anything more modern/quiet/reliable to put on? These are what the Mercedes guys sold me, so I figured they would work best, but it's getting expensive to keep doing this. The compressors are warranteed, but the labor and a/c service adds up!...On a brighter note, this forum has been outstanding in helping me diagnose and solve the rest of my problems, thanks people!

I have a GM compressor on my SD. There are others who are using GM compressors with no problems. They're certainly cheaper, and they do the job correctly.
-Joe

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

Will the GM compressor bolt up? Do I have to make up new hoses? Will it go more than 2 days without falling apart? lol

Go see Jack at Arizona Auto Air (ackits.com) in PHX. Sounds like something isn't right with that system. They shouldn't make that much more noise. Was a ND compressor stock on that model year? I thought all the 617t's were using R4s. Maybe someone cobbled together a compressor and used the wrong brackets.

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84 300DT Puke Yellow. Totalled after 438,000
84 300DT Orient Red. 169,000 (actual mileage may vary)
2002 Explorer EB (wife's)

The 1981 300SD can use a Delco GM or R-4 compressor. I think ND compressors were for W126 models and other benzes after 85.
-Joe

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

The delco piston type compressor drains more power out of my 380SEL than I like to think about (its a new one too). If I were changing it again, I'd definately go for a Jap vane type compressor (quieter. less power drain).

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Andrew
300e 294,000mi
380sel 185,998mi
380se 309,980mi

I'd be real surprised if you had something other than the GM R4 compressor on that SD. In my opinion they are good compressors as long as you don't try to rebuild them. You should be able to make it work in your application.

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Jim

Well, upon further review. It is an R4, and a remanufactured one at that! Is this my problem? Is there a vane type available? I'll go see the guys at Arizona auto and get this straightened out.

I had a somewhat similar problem. I got my A/C system converted to R134a and I replaced the compressor, receiver-drier, had the system vacuum and then charged. Two months later, I was driving around town and the belt snapped ( I heard it). The mechanic told me the compressor had locked up. So I got a warranty replacement but I still had to pay for labor to get the entire system setup again. Then after all that was done, a week later (actually just yesterday) the compressor started making all the same noises yours was making, and yes, while idling at a traffic light people in other cars looked funny at me. So I took the car back to the mechanic and all he needed to do was tighten the belts and the noise disappeared.

Just take the car back to the people that did the compressor replacement and tell them about the noise. It could just be a loose belt like on mine. Good luck.

If the system is not THOROUGHLY and TOTALLY flushed CLEAN, the new compressor is destined to fail, period, end of story.

If it is noisy, it might run a long time making noise, or it may quit before you can make it to the office this morning. Either way, replacement and flushing will cost the same. It would be a good idea to seek out and find a suction side filter and install in the low side line leading to the compressor. Even if you do that, flush it anyway.

BTW, to answer your original question, yes there are beaucoup compressors better than the R4. This was a terrible choice by MB IMHO. That said, it's not worth the trouble to retrofit with a different compressor. Either way you MUST flush. It will be MUCH cheaper to seek out a NEW, not rebuilt R4. If the system is properly flushed, you can make it live for a long time, even longer if you will spend an extra 50 bucks or so for R12 when you do the job. You will have to flush and replace r/d anyway, it would be a great time to put it back together properly.

Good luck,

The R-4 can rattle on for a very long time, if you can live with it. I put an $89 reman R-4 on my 123 diesel in about 1994. (Hey, it was pre-Mercedesshop and I didn't know any better...) It was starting to rattle when I sold the car in 1999, but didn't die until 2001. I would have replaced it because the noise was so bad, but I sold it to a cheapskate friend who never repairs something until it's *really* broken.

The general concensus around here is to only purchase a brand new R-4. They're relatively cheap as compressors go. I seem to recall some discussion of cheap, Asian manufactured knockoff copies of the R-4 that don't last too well even from new. Be sure to get the real thing.

- JimY

Ok, now I'm mad. My local indy mechanic "converted" my system to 134a simply by adding the new fittings. The R4 compressor will not take the higher pressures of 134a, due in part to the insufficient condensor and receiver. I'm probably lucky not to have blown any of my old hoses! To make a long story short, at an idle the pressures rise rapidly and my compressor starts knocking and pinging and gagging. At higher speeds, it does just fine. Now I have to clean the whole thing out again and go back to R12. When I bought the first compressor they just ASSumed that I was putting R12 through it, (despite the fact I specifically mentioned 134a), and that brings us to where we are today....*sigh*

Astroman,

What are your pressures? It could be that it is overcharged. 134 has a nasty habit of getting into sort of a "pressure runaway" condition. In a converted system you have to add just a little and give the system time to stabilize then monitor your pressures, then add a little more, stabilize and so on.

If it is overcharged it could certainly be the reason for your noise.

I'm certainly not a proponent of conversion, but if it is already converted and you can get the pressures right you might be okay. The R4 is not a real bad candidate for conversion. If you do have trouble from high pressure it is more likely to be the compressor than a hose or other components. At least that has been my experience.

Reverse converting would be a good step, by I wouldn't do it unless you just can't get things right with the conversion. Reverse converting is a pretty major project if you're going to do it properly.

Good luck,

Thanks Larry. Why is reverse conversion such a big job? Like I said, all my mechanic did was add the 134 fittings, seriously...I'm just going to disassemble the system a little bit, flush everything out, blow it all dry, replace the receiver/drier, add oil, reassemble, vacuum it down and add r12. Nothing else was touched. Do you know something I don't?

You also should remove the compressor and pour/pump out as much oil as you can, put in a little mineral oil and pour/pump that out to rinse out the compressor.

I consider breaking all connections and thoroughly flushing etc., to be a pretty good size job. It's not all that bad, but I guess I said that because I thought that you might not know that you need to do all that to properly reverse convert.

Good luck,