Compressor Bad?
 

I picked up an '81 300 SD three weeks ago. Over the past two weeks I have had a problem with the belts squeeling. It seems to happen only once the car has warmed up a little, and happens sitting at idle as well as while driving. I [I]think[I] it's happening just when the air conditioning is running, but here in Florida that is almost always.

I checked the belt tension, and that seemed fine to me. I applied belt dressing, with little improvement made to the intermittant squeel.

Yesterday, the squeel stopped. :) I think that was due to the compressor belt breaking. :(

Do I have a compressor that has the bearings seizing up? Is there a way to check it?

On prior inspection of the belt, it did not appear overly worn, but it certainly wasn't near new either.

I'm very mechanically challenged / ignorant. I would hate to go through the hassle of changing out the belts only to have the squeel re-appear and break another belt. Any suggestions are greatly appreciated.

I would also like to know if anyone can recommend a reasonable MB repair shop in the Vero Beach, FL area.

Thank you

Try to turn the compressor by hand. If you can't then that is probably your problem. I have seen the clutch lock up on them doing the same thing you are describing.

A belt doesn't just break for no reason. Examine the belt. Was it on the vehicle since it left Germany? Is it an aftermarket POS? Is it a US equivalent that is narrower than the specified metric belt? Are there signs that the belt should have been replaced long ago?

If so, then install a proper new Continental belt that fits the pulley properly. Tension it to the required level and try it again.

If the clutch is seized, you'll see smoke pouring out from the new belt and the noise will be horrendous.

I know that sound, happened to mine a week ago. :o

When you turn it by hand, make sure you are turning the center part of the pulley, not just the outer portion. The outer portion should turn easily (without a belt). The center will be harder to turn, but it still should turn by hand.

Thanx
 

Thank you for the tips. I outer part of the pulley moves freely when I turn it by hand, but I didn't know if that really told me anything or not, as I thought it may only be seizing up when a clutch inside the compressor was engaging. Tomorrow, when I have daylight, I will try turning the center portion of the pulley. As you can tell, I am pretty ignorant about this.

As I said in the original post, the belt was not new, but at an earlier inspection I did not see any signs of gross degredation or undue wear. Not enough left of the belt now to really tell anything.

I never did see any smoke pouring out while in motion or at idle.

Craig,
You said you had the same thing happen to you a week ago. Did it turn out to be a compressor problem?

If you're lucky, the belt was just old and it broke. If you're not so lucky the compressor seized and broke the belt. Let us know what you find.

My compressor seized in a big way, the entire front of the clutch was missing when I stopped. The clutch bearing also seized and stopped turning, resulting in the belt pretty much melting off. I cut off the belt and drove home, I now have a new compressor installed.

Inner part of pulley moves
 

Craig,
I tried your suggestion first thing this morning. The outter part of the pulley turned freely. The inner part was much stiffer, but still turned. I applied pressure by hand against the edge of the triangular shaped plate on the front of the pulley. I turned it a couple of revolutions both clockwise and counter clockwise.

I hope this is a good sign that maybe I won't be wasting my time putting on a new belt.

Thank you

That is a positive sign that the clutch and compressor will turn. Install a new belt and hook your gauges hooked up to the system to insure that your pressures are where they are supposed to be when the compressor is in operation.

I don't have the guages, or the knowledge to use them, but I will put on a new belt. Hopefully, I will get to this tomorrow when I get off shift in the morning. I'll report back the results.

Thank you

After market compressor?
 

I started calling the local auto parts stores to find the belts I need. According to Auto Zone, there are 2 possible compresors that may be on my '81 300 SD. They need to know which one I have to give me the correct belt.

I got underneath the car to look at the label on it and it says "Harrison General Motors" Does that sound right? What do you make of it?

Auto Zone was the only place that mentioned the need to know which compressor I have. The other places I called never questioned me.

There you go again.

Heading down the same path and obtaining a POS belt from AutoZone that probably will be too narrow for the sheave.

You own a Mercedes-Benz, not a POS Chevy. Obtain the proper belt from a proper supplier (FastLane or the dealer)........or suffer the same consequences.

I agree with BC on this. I don't know how many MB's I have seen with belts that came from Advance Auto or a place like that and the fit in the pulley was not what it should have been.

I, to, have been disappointed in the past with certain parts from Auto Zone, Advanced Auto Parts, NAPA, and some of the others, but part of the issue is conveinence and my impatience. The closest MB dealer is 45 minutes away from me, and the wait on something mail order is at least 5-7 days unless I pay a huge price for expedited shipping.

Check out the forum entitled "Fastlane feedback". It's accessed from the first page. Most folks who order parts from Fastlane get them in two days or less because they use the closest WorldPac warehouse. And, if you get the order up to $100., you don't pay a dime for shipping. Otherwise, you pay actual UPS shipping costs.

So, your excuse to use inferior parts is eliminated.

Thaks for the tip, Brian. I continue to learn more and more all the time.

The outcome...for now
 

I said I would report back, and here it is. I received the belts and changed them out. Thanks to the great tips on this site, with a little patience, it did not prove to be too difficult of a task for me. That's the good news. I do continue to second guess myself as to how much tension to put on them. Any good rule of thumb for this novice?

Within moments after starting the engine, the power steering belt began to abrade slightly on its edges. I can see that the pulley on the power steering pump is not spinning 100% true and attribute that to the cause.

The bigger issue continues to be the A.C, compressor. I no longer have the squeel that started this ordeal, but with the A.C. on there is a noticable, rough sound. Some what irregular, like a few pieces of gravel being slowly shaken in a box. Almost like the sound of a playing card in a childs bicycle spokes, but irregular, as mentioned above. Once the A.C is turned off, the sound becomes much less noticable and the faint growling that is heard has a regular rhythm. Sorry that I am not better at describing the sounds, On the bright side, at no time while letting the car run for the 10 minutes or so did I hear the awful squeel.

I guess I'll wait and see what the compressor or belt throw at me next and try to decide on a course of action based upon that.

Thank you all for your help and suggestions and as a novice I welcome any further insights you may have.

That Harrison compressor is a POS General Motors spec R-4, with MB spec of a 9 o'clock clutch placement so the wire hook up is at 3 o'clock when looking at it from the front. The gravel sound you hear is the compressor getting ready to sieze up. Sometimes they will sieze up for a moment and let the belt snap then release. Other times the lock up hard. You need to turn it again by hand in the direction the pulley spins. Some time you can turn them 3 or four time, then you feel it lock.

I cut my teeth on the POS R-4 working for a Cadillac dealer. I replaced more of those than I care to remember during my summer of high school employment.

Why MB used a POS GM part makes no sense.

Does synthetic oil help?
 

I too am working on my ACC. I determined that the low pressure switch on the dryer is either bad or there is not enough pressure in the system. If I bridge the wires that go to the pressure switch, the compressor clutch engages and the compressor turns freely. AFAIK it still has R12. I recieved a set of guages in the mail today and will check my pressures when I get home.

Now the question: I read the writeup Diesel Giant did on replacing the compressor and using synthetic oil. Does anyone know if this really makes a difference in the long term. Will it really make these POS compressors last longer? Does anyone have real world experience with this?

The sound I had was a horse walking on cobblestones, or perhaps a marble in a clothes dryer.

Belt tension was the problem. I bought a kriket tension gauge at NAPA for $10, found the belts loose, and the noise went away when the belts were tightened properly.

This was on a newly installed reman R-4, with all new Conti drive belts (from Fastlane :D )!

On borrowed time
 

Just got back from picking my son up. boy, was he embarrassed for his friends to hear the sound the car is making.

I have a better description of what the sound has developed to,the sound is back to what I originally heard when this ordeal started: Fingernails down a chalk board. Not constant, but with some regularity. When it's not making that sound, it's the rough gravel sound.

I guess the POS belt from Auto Zone, that I wouldn't have had to wait for and could have had for half the price of the one I bought, would have worked just fine for this application:behead: I guess I'll run it until it seizes up all together and then go from there:mad:

Check the tension. Using the Kriket gauge was a real eye opener. Properly tensioned belts were WAY tighter than I would have guessed by feel.

All noises stopped for me when the tension was correct.

Thank you for the suggestion. I'll pick up the Kricket tool tomorrow, but I don't expect that to be the answer to my problem.:mad:

I'll bet you the "rock tumbler" sound you're hearing is being caused by the compressor belt not having the right amount of tension. They have to be really tight to funcion properly and not make that noise. I went through a major a/c overhaul last month because the clutch on my compressor had seized, a new compressor with the stepped ports, not a remanufactured unit. My belts were old anyway and I was getting that sound. I tightened it up, the noise went away, and the belt promptly snapped a week later. I've got a new belt and a new remanufactured compressor on there and the belt is slipping a little at highway speeds(higher constant rpm) but its fine around town as long as I don't go over 35 mph. I checked the belt tension with my thumb and its stretched into place over the last three or four weeks so it needs tightening. I bet if you tighten yours the noise will go away.

As I said, I will pick up the Kricket guage that has been recommended, but from what I'm reading here, I guess it's best to have the belt too tight and err in that direction as oppossed to not tight enough.

When the time comes, probably sooner than later, for me to get a new compressor, what is the best source and manufacturer you recommend?

Watch out for the offshore stuff
 

Go with a GM or Harrison compressor. I don't know if rebuilt is as good as new or not. In my experience with other rebuilt parts it is a crapshoot. I know putting a compressor in is a major deal for a DIY, so I would tend to go with a new one, and I would stay away from any off brand.

You may also want to search other threads for R4 compressors imploding. I think there is the possibility of sending chards of metal into the system if the compressor self destructs. There has also been much discussion about the amount of oil in the system. If some of the oil has leaked out you don't know how much to put in to make the system right. Too little and it reduces the life of the compressor and I think too much also has detrimental affects. I think the only way to know for sure is to start from scratch by removing the compressor, dumping the oil, refilling with the correct amount, etc. Do a search for Diesel Giants AC compressor replace and flush write up. It is very good with excellent photos. He also uses synthetic oil in his system.

When I did this job last month, I went with a rebuilt unit.

My theory is that most of the bad rap the R-4 gets is due to the higher head pressures encountered with R-134a conversions. Since I stayed with R-12, my head pressures should be within the original design range of the compressor, and lead to longer life.

The second reason (and the deal sealer for me) was that the new compressors come with "stepped ports". This means the suction and discharge ports are on slightly different "planes" at the manifold connection. In order to get a seal, you have to use seal rings, which are metal/rubber combos that raise the sealing surface on the lower port up to be coplanar with the higher port. There have been numerous reports of getting leaky seals at the manifold using these seal rings since our manifold hoses have "non stepped" or coplanar ports. I think all new R-4's come stepped, remans come both ways. I bought the compressor locally, so I opened the box to examine the ports before purchase. When I saw non-stepped, the deal was closed.

The last reason was price. $108 for reman, $220 for new.

No Kricket guage to be found
 

Techguy512,
Thanks for your input. When this compressor completly gives up the ghost, I'll have my mechanic put in the replacement, but I will discuss your thoughts with him.

I went to NAPA, Auto Zone and Advanced Auto looking for the Kricket belt tensioning guage you recommended, all to no avail. No one had even heard of such a thing.

I guess I'll pop the hood and just tignten the belt to the point of having it as taut as possible.

I got mine at Napa. It was a cheaper, plastic version of this one, sold under the part number KR-1:

http://www.midwayautosupply.com/detailedproductdescription.asp?13199

Better, for now
 

Techguy512,
thanks for the link as well as the NAPA part #. I'll be going back to NAPA with that information in hand. You wouldn't have believed the funny looks I got from everyone in there when I asked about it.

Thanks in part to your input as well as Sailor15015, I went and re-tensioned the belts. They had stretched some from when I first put them on. I have them now to the point that I am almost uncomfotable with the amount of tension on them, but I remind myself that I know next to nothing about this stuff, so my intuition on this topic is useless.

Since tightening the belts and letting the car run in the driveway with the A.C. on for the past 30 minutes, the squeel has not returned. I do not believe that I am fortunate enough to dodge the bullet this easily, so we'll see what the next day or so brings.

To further demonstrate my ignorance, can someone explain to me what problems may be occuring due to a thin oil very slowly dripping out of a canister that is located in the front left of the engine compartment and is clearly part of the A.C. system? The canister is about the size of the main fuel filter and has A.C, lines and fittings on it.

Are you sure it's A/C related? Where is it exactly? On the W123, the A/C suction line runs right under the power steering pump. The way it is positioned does make one think it is connected to it some how.

It is possible that you are seeing the dryer as well, but dryers are usually not mounted on the engine. If it's oozing oil, it could be a loose fitting or a bad o-ring.

It's not mounted to the engine. It is in front of the engine, next to what appears to maybe be a transmission cooler (looks like a small radiator hanging next to the radiator) The canister that I'm talking about has a couple of lines running to it and some fittings, that I guess guages could be hooked to. there is some grey RTV looking sealant over one of the fittings.

With the earlier post about oil in the A.C. , I thought that this may be some componant of the A.C system that contained oil.

Sorry that I don't know what I'm talking about.

Are you sure that "small radiator hanging next to the radiator" isn't the oil cooler? If that is leaking you need to repair it immediately. If it leaks under pressure your engine will run dry in no time. You can find pictures of the oil cooler on diesel giant's site: http://dieselgiant.com/oilcoolerlinereplacementl.htm.

My AC compressor seized a couple weeks ago and I won't get around to replacing it for a while, which really sucks as I live in Tampa. It chewed my belt after it made the "about to seize" bearing noices. I found a good German Mercedes/foreign mechanic 'Ludek' here in Tampa if you want his contact info let me know. BTW he says get a NEW compressor, not rebuilt. And to ensure warranty you must flush the system and replace the dryer/accumulator (I think he said both).

Can you take some pics of it? RTV around a fitting is usually some ones bad idea of a quick repair. What color is the oozing oil? Black is engine, red is tranny, clear or red can be power steering, depending on what is used. Engine coolant also has an oily feel to it when the water has evaporated. A/C compressor oil is lightweight like mineral or 3 in 1 oil.

We do not want it to be engine oil, because as posted by BLHFLA, you can run your engine dry of it's life blood.

It sounds like you are refering to the accumulator/drier, most likely in the high side of the AC system. Some systems have either the accumulator/drier in the high side or a reciever/drier on the low side. The low side will be the larger size pipe. If your compressor locks up you need to replace either drier you have as it will be full of crap from the bad compressor. Also you should flush the system out, change all the O-rings on all the fittings. I also suggest getting a NEW compressor, the remanufactured ones are big time crap! :mad:

Here is some more information from poster "Fletch944T" at Clark's Garage Message Board -

"I believe that NAPA, Autozone, and Carquest all sell the Krikit tool. It's actually made by Gates (the belt company) and the Gates part number is 09001 (for the Krikit I). The odd thing is that Porsche sells the Krikit tool under part number 000 721 957 40 for the 911 which they call Special Tool 9574. Porsche charges about $40 for the tool. However, there are three versions of the Krikit tool for different tension ranges (Krikit I, II, and III). I'm not sure if the one sold by Porsche for the 911 is the correct range for the 944. The one you need is the Krikit I. You can get it at NAPA for about $10."

Per Mr. Fletch, the one you want (and the one referenced by Napa P/N KR-1) is the Krikit 1.

Thanks for all of the replys. The "small radiator" that I thought may be a tranny cooler is the oil cooler. It's not leaking.

I think the part I'm asking about may be the drier/accumulator. I doubt I'll get a pic up for confirmation before Sunday at the earliest. If I'm right, could it be leaking oil?

If I do need a new compressor, I guess the shop will take care of this item at the same time.

Tomorrow I'll try to track down the Kricket guage for future use.

Again, thanks to all of you for your replys and help.

forgot to add that the oil is a very light oil. Could pass for 3 in 1 oil

Does it look like this?

Based on the specified location, I'd go for the power steering reservoir. This also has some heavy duty lines going to it.

Here's the pic
 

I believe that the image techguy512 has posted is the part that is leaking the oil. With the help of a co-worker, I am trying to post a couple of pics of this item that is located pretty much just behind and below the left headlight.

I hope these pics come through.

Does your AC blow cold?
 

Have you determined that when you turn on the AC that the compressor clutch is engaging when you turn on the AC. Look at the compressor and you will see the front face of the compressor turning when the AC is on and not turning when the AC is off. If it is engaging, is the AC cold?

If you are leaking oil from the dryer (the part that techguy512 posted the photo of) you should not be running your AC because you are losing the oil that lubricates the compressor.

E-mail address
 

I tried to send the pics and probably did not go through. I would like to know if you could send me your private e-mail so I could send them that way and then post them on the forums.


Thanx.

You now have a problem. Since you don't know how much oil you've lost, you don't know how much to replace. Your options (in conjunction with sealing the leak) --

1) Open the system, flush everything, replace dryer and maybe the expansion valve, fill with the FSM recommended quantity of oil compatible with your refrigerant, and charge.

2) Guess at the quantity of oil you've lost, and use an oil injector to introduce a measured quantity of oil into one of your service ports. I would try this only if you know what kind of oil is already in the system, and you can get an additional quantity of the same oil. I would never suggest mixing oils, even if they claim compatibility.

Obviously, option 1 is preferred.

The front of the compressor is turning, so I guess the clutch is engaging. It is also blowing cold. What you say about it losing lubricating oil and causing damage makes sense. Can any A.C. shop replace the oil? Is it a simple enough DIY that someone like me without any A.C. experience can handle?

Question answered
 

Techguy512's post came at the same time as mine, and answers my question.
Thank you.

If you want to fix it to last take everything apart, flush it all out and replace the bad parts. Put correct amount of oil in it, vacuum for as long as you have time, charge it and go.

I know the re-build is beyond the scope of my knowledge and ability.

How much should I expect to pay to have this done?

Is there anything in particular I should mention to the mechanic to avoid being taken for a ride and having him do more than is needed?

I guess this is something I should schedule ASAP.

My guess is $600 to $700
 

If you go with a new compressor and have the shop put it in, and vacuum it down and install refirgerant. Go with R12 if you can. It is what was originally specified for your AC system. You will also have to replace the dryer. But if you can not seal the system again because of the current leak then all the work is for nothing. It doesn't make sense to me that it would be leaking oil from the dryer and still blow cold because it would also be leaking refrigerant.