81 300SD replacing drive belts - PeachParts Mercedes-Benz Forum

El Ted · #1 05-08-2015, 06:59 PM

Hello All!

Looking to replace the drive belts on my W126 300SD.
The water pump/alternator belts are the ones needing to be replaced, esp. 1 of them.
It seems apparent, I have to remove the A/C & P/S belts before I can get to the 2 belts mentioned above.
I can't seem to locate the tensioners for the A/C compressor.
Also, any advice on how to loosen the tension on P/S and alternator would be appreciated. I rather be turning the right nuts, then finding out later, what I did wrong.

Thank you, fellas!

Skid Row Joe · #2 05-08-2015, 07:11 PM

When you get under there and look around, all the adjustment screw/bolts are readily visible. The W126 300SD is a pretty easy MB sedan to wrench on. I did A LOT on mine back when I owned and drove an 83 300SD. Great cars!!!

yuke · #3 05-09-2015, 11:02 AM

Pretty sure the a.c. p.s. + alt. each have 3 mounting bolts that have to be loosened and then the adjuster to adjust them. The a.c. adjusting bolt is right against the fender well and is very hard to get at either from top or bottom a 10mm wrench it takes I'm pretty sure. Thats on my 85 300 S.D. Hope this helps.

vstech · #4 05-09-2015, 11:33 AM

Yup. 3 bolts each accessory plus an adjuster bolt.
The power steering is all 13mm bolts with nuts on the back that need to be held. Universal joints are needed. Careful around the fuel lines. They get brittle. The adjuster is on the mount top.

Then it's the ac bolts. 3 17mm bolts that are on the back of the compressor. On various length spacers... then the adjuster is on the bracket near the oil cooler line mount... 10 mm DEEEEP SOCKET or a gearwrench...
Then on to the alt/water pump pair... GET CONTINENTAL BELTS! They need to be true 10mm width belts. Length should be 1035 on the 82. 83 and up use 1000 length.
The BRACKET of the alternator has 3 19mm bolts I think... maybe 17mm, holding the bracket all from the rear of the alt. When all 3 are loose, loosen the 13mm adjuster. Soak it in aerokroil first for a day. It's fragile and needs to move freely

ROLLGUY · #5 05-09-2015, 01:57 PM

Quote:

Originally Posted by vstech

Yup. 3 bolts each accessory plus an adjuster bolt.
The power steering is all 13mm bolts with nuts on the back that need to be held. Universal joints are needed. Careful around the fuel lines. They get brittle. The adjuster is on the mount top.

Then it's the ac bolts. 3 17mm bolts that are on the back of the compressor. On various length spacers... then the adjuster is on the bracket near the oil cooler line mount... 10 mm DEEEEP SOCKET or a gearwrench...
Then on to the alt/water pump pair... GET CONTINENTAL BELTS! They need to be true 10mm width belts. Length should be 1035 on the 82. 83 and up use 1000 length.
The BRACKET of the alternator has 3 19mm bolts I think... maybe 17mm, holding the bracket all from the rear of the alt. When all 3 are loose, loosen the 13mm adjuster. Soak it in aerokroil first for a day. It's fragile and needs to move freely

The 3 A/C bolts take a 19mm tool, the alternator takes 17mm and 13 for the adjuster.

tyl604 · #6 05-10-2015, 05:17 PM

You will appreciate the tensioners. On my '57 Chevy I used to lever with a 2x4 with one hand and tighten with a wrench in the other. Tensioners are great.

vstech · #7 05-10-2015, 09:34 PM

Quote:

Originally Posted by tyl604

You will appreciate the tensioners. On my '57 Chevy I used to lever with a 2x4 with one hand and tighten with a wrench in the other. Tensioners are great.

I LOVE all the tensioners in these cars! I've worked on thousands of cars and hate needing a crowbar for some of them

Skid Row Joe · #8 05-10-2015, 10:20 PM

Quote:

Originally Posted by vstech

I LOVE all the tensioners in these cars! I've worked on thousands of cars and hate needing a crowbar for some of them

You betcha, big guy!

These are an absolute dream of a car to work on. I am still open to buying another one. Wish I'd of kept mine 16-years ago! Easiest car I ever worked on that got me to 300K miles with ease.

sleepstar · #9 05-11-2015, 02:32 AM

you can hit the 10mm on the A/C with a crowfoot too, but its annoying.

toomany MBZ · #10 05-12-2015, 07:34 AM

The attachments are from the FSM.

El Ted · #11 05-12-2015, 09:31 PM

Thank you guys, you're absolutely awesome!
I've done it in the past. But it's several years ago, so I don't remember.
I didn't want to waste too much time on it. My mech can flip them in 30 min. or less, without much wrenching.
With this valuable info, I should be able to do it in an hour or less and save a little money.

Ps, I think I'll leave the a/c belt off anyways. I never use a/c.

toomany MBZ · #12 05-13-2015, 07:28 AM

You're welcome.