'81 300SD What do I loosen? - PeachParts Mercedes-Benz Forum

tyl604 · #1 02-26-2017, 08:24 PM

Well, the bearing sound was not the water pump. So what bolts, etc. do I need to loosen to remove the belt to the AC? I think the sound is a bad bearing in the AC condenser or maybe the idler pulley.

Can anyone tell me what to loosen?

Thx.

ROLLGUY · #2 02-26-2017, 08:39 PM

Quote:

Originally Posted by tyl604

Well, the bearing sound was not the water pump. So what bolts, etc. do I need to loosen to remove the belt to the AC? I think the sound is a bad bearing in the AC condenser or maybe the idler pulley.

Can anyone tell me what to loosen?

Thx.

If it is an R4 (I assume it is), loosen three 19mm (tool) bolts. They are facing the rear of the car. Then loosen the adjustment nut on top (10mm tool). If the A/C is inop, you may just want to cut the belt. It can be replaced later if/when the compressor is replaced.

Alec300SD · #3 02-26-2017, 08:46 PM

Three bolts need loosening, see V-belt B, Step 1. on the FSM job 13-340

tyl604 · #4 02-26-2017, 09:06 PM

Thanks guys; just what I needed. Was pretty disgusted after installing the new water pump to find out that there was nothing wrong with the original one. Got to be the AC bearing. Wondering also if I could be lucky and it is a bearing on a yet not located idler pulley (if such exists). What a terrible noise.

ROLLGUY · #5 02-26-2017, 09:11 PM

Quote:

Originally Posted by tyl604

Thanks guys; just what I needed. Was pretty disgusted after installing the new water pump to find out that there was nothing wrong with the original one. Got to be the AC bearing. Wondering also if I could be lucky and it is a bearing on a yet not located idler pulley (if such exists). What a terrible noise.

No idler pulley. Could be the alternator making the noise also.

tyl604 · #6 02-26-2017, 09:33 PM

Roller - I have a new alternator so hoping that is not it.

I see an idler pulley and a stretch bolt under Pelican's parts. Should be for a 1981 300SD per Pelican??? Looks like the pulley has a bearing.

sixto · #7 02-26-2017, 10:36 PM

Otto's '81 SD doesn't have an idler pulley. My '83 doesn't either.

Did you get a good quality alternator? I got an Autozone alternator that didn't make it very far before seizing.

How's the power steering fluid?

Sixto
83 300SD
98 E320 wagon

tyl604 · #8 02-27-2017, 08:55 AM

It is for sure not a power steering groan; I would recognize that. Got a Pep Boys alternator - don't laugh - and hope it is OK. I may not have an idler pulley either; have to go out and look when weather gets better.

tyl604 · #9 02-28-2017, 07:05 PM

It was the AC compressor. When I got under the SD, I could rattle the pulley on the compressor even with the belt attached. So I removed the belt, started it, and presto the bad bearing sounds were gone. Back was the sweet sound of the diesel (well as sweet as possible).

I did loosen the bolts and the belt tightner and removed the belt from the pulley; however, you cannot remove the belt completely without also removing the belt on the power steering. So I used my handy tin shears and cut the AC belt.

So question about the compressor - is it possible that I could have the pulley and bearing replaced or do I need a whole new compressor? It is an R4 with freon and I replaced it myself maybe fifteen years ago. Have not had AC for a couple of years because all the freon has leaked out. Not sure whether I need a whole compressor.

Not sure you can hear the difference in these two videos. First one is with the belt attached and the clatter from the pulley on the compressor; the other is after I removed the belt. Have not uploaded a video to Peachparts before so not sure I know how to do it. OK - it worked. I can actually hear the difference - clatter vs no clatter.

http://vid303.photobucket.com/albums/nn151/adraintaylor/Vid%2030SD%20with%20belt_zpsvyfyedec.mp4

http://vid303.photobucket.com/albums/nn151/adraintaylor/Vid%20300SD%20belt%20removed_zps61ystnfr.mp4

Dan Stokes · #10 02-28-2017, 08:17 PM

I'm not sure who makes the Mercedes compressors but generally the front clutch assembly is a serviceable part on most. There's a fairly simple procedure to pull the clutch and put on the new one. If you're doing the job it's a good plan to also change the front seal, again depending on the design of the pump. Easy now, harder later. Then find the leaks and fix 'em - you would be surprised at how often it's just a $0.50 seal though of course it can be more pricey stuff, too.

Dan

tyl604 · #11 02-28-2017, 09:06 PM

Dan - confused when you say front clutch. The belt runs on a pulley at the back of the compressor and that pulley which is a part of the compressor is what is rattling. Are you saying this is the front clutch and might be repaired?

ROLLGUY · #12 03-01-2017, 12:53 AM

Quote:

Originally Posted by tyl604

I did loosen the bolts and the belt tightner and removed the belt from the pulley; however, you cannot remove the belt completely without also removing the belt on the power steering. So I used my handy tin shears and cut the AC belt.

Too late, but you could have worked the belt around the power steering pump pulley in such a way that it is stored up high around the PS pump, held with zip ties. When the compressor is replaced, the belt can be put back and reused without removing any other belts. Next time this trick will come in handy (R4's need replacing often, they usually don't last as long as the belt)......Rich

tyl604 · #13 03-01-2017, 08:43 AM

Thanks for the heads up. So can the compressor be rebuilt or am I barking up the wrong tree?

If I just remove it and fool around trying to fix it, will it be bad letting air get into the system? Or maybe I should cut a plate and bolt it over the hole using the compressor as a guide?

Next the drier is only $22 at Pelican but do I really need to replace it? I seem to remember in the 1970's that in my Oldsmobile Cutlass I just opened up the drier and replaced a canister or something and then put the top back on. MB engineers did not design ours for something easy like that?

ROLLGUY · #14 03-01-2017, 09:51 AM

Any time the system is open to the air, the drier needs to be changed. Also, you will need to flush the entire system if you replace the compressor. All of the old oil needs to come out so you can know how much oil is in the system (meaning you must start with a clean system). Rebuilt compressors are available, as are new ones. Personally, I would not waste my time on any R4. It is not the greatest design for a compressor. It does not have it's own oil sump, so it gets lubricated by the oil flowing with the refrigerant. When the refrigerant escapes (leak), the oil goes with it. If you have 25+ year old hoses, they may be leaking as well. If you want a long lasting system, you will need to replace all the components (drier, hoses, TXV, compressor, pressure switches etc). With the R4, even then it is a crap shoot (the crap I am referring to is the R4

). The other option (best in my opinion) is a Sanden retrofit.........Rich

tyl604 · #15 03-01-2017, 11:17 AM

Good info. Thx.