Weird Serpentine Belt Issue 1987 300D - PeachParts Mercedes-Benz Forum

iamtheosprey · #1 10-17-2014, 08:51 PM

So, I noticed that my water pump was weeping and there was some bearing noise coming from that general area so I ordered the parts...(yes, from PeachParts and the experience was flawless and so were the parts). I got a belt locally, bought the water pump and a new tensioner pulley from PeachParts.

I took everything apart today and noticed that the old tensioner was grooved from wear so that was a good idea to buy in advance.

So, I reinstalled everything and I noticed that the belt was touching itself between the water pump pulley and crankshaft pulley.

I figured it would sort itself out when I reattached the tensioner spring and damper.

However, once I got the car back together and fired it up there was noticeable belt screech and I noticed the the lettering on the smooth side of the belt was wearing.

From a low rpm takeoff and when I accelerate the belt screams like the dickens and I'm pretty sure it's because it is touching itself where I described earlier.

I checked the diameter of the tensioner pulley and it was the same as the old one but the old one had a belt wide groove in its center lowering the working diameter.

Occasionally I would hear a belt screech before I replaced this one but never like this.

The old belt was fine but it came on the car and I've driven it forty thousand miles since I bought the car so I will carry it as my backup.

I'm positive I got the belt routing right but I noticed right away the belt would be rubbing itself.

Is this normal?

I guess eventually it will wear down but I don't want to weaken the belt from a loss of material and heat.

On a lighter note, I did notice that my temps were lower after fresh antifreeze and a new water pump.

By the looks of the old antifreeze I think it could have been pure, undiluted antifreeze.

97 SL320 · #2 10-17-2014, 09:17 PM

Positive you have it routed correctly because the tensioner works or positive because it matches a diagram in a shop manual?

There is a chance that the water pump or crank pulley has been changed sometime in the past. You wold have top get someone with this year / engine to have a look / post a pic.

TMAllison · #3 10-17-2014, 09:24 PM

I believe you have the same tensioner setup as the 606? A spring (with damper) that puts tension on the roller pulley/tensioner arm?

Is it possible the spring is for the wrong model and isn't creating sufficient upward pull or that the tensioner arm is wrong? Also possible that the damper (shock) is worn.

vstech · #4 10-17-2014, 10:20 PM

If the belt is touching between wp and cp you have too thick a belt
http://www.peachparts.com/shopforum/attachments/diesel-discussion/32003d1141705372-om603-serpentine-belt-routing-603pulley-layout.jpg

vstech · #5 10-17-2014, 10:30 PM

Also, if you have the belt inside out it will rub, as the belt will be riding on the ribs...

iamtheosprey · #6 10-19-2014, 09:10 PM

Well....I stand corrected...

I said to myself that I should have taken a picture just as I pulled the old belt off.

Then I looked to see if there was a sticker on the chassis and there wasn't one.

It was also pretty damn hard to get the belt on the way I had it routed.

I drive it this way for about 200 miles yesterday getting up to 100mph at one point.

How likely is it that I screwed something up?

Basically the way I had it routed it was wrapped around the water pump pulley, around the tensioner, back to the alternator to the crank and to the AC compressor and PS pump.

I just put it on correctly and it was way easier.

I'm going to test drive it now to see if I notice anything wrong.

Quote:

Originally Posted by vstech

If the belt is touching between wp and cp you have too thick a belt
http://www.peachparts.com/shopforum/attachments/diesel-discussion/32003d1141705372-om603-serpentine-belt-routing-603pulley-layout.jpg

vstech · #7 10-19-2014, 09:32 PM

Likely the belt is damaged. I would put on a new one.
I recommend true MB belts, but continental brand is just as good.

vstech · #8 10-19-2014, 09:34 PM

1987 Mercedes-Benz 300D Base Sedan - Filters & Belts - Page 2

iamtheosprey · #9 10-19-2014, 09:41 PM

Quote:

Originally Posted by vstech

Likely the belt is damaged. I would put on a new one.
I recommend true MB belts, but continental brand is just as good.

I had the water pump and tensioner pulley under so much tension I suspect I did about 10K miles worth of wear on the bearings.

I could hear the water pump bearings with the wrong routing.

I checked the belt but didn't see any obvious problems.