603 serpentine belt tensioner - pulley at an angle
 

I was just killing time at work and noticed this

http://www.mbz.org/info/articles/engine/60xeye/

The text of which is ...

60x Engine - Things to keep an eye on
By Marshall Booth

Something to check is the idler pulley on the serpentine belt tensioner - make sure it's parallel to the belt. If it's NOT have it serviced - NOW. If the tensioner lets go and strips the threads in the timing cover it's big $$$$. Worst case if caught early will be ~$300 or less.
Not much else to worry about. If the oil level light comes on - check the oil level and if it's okay, don't worry - they are notoreous for lighting up on a random basis.

The alternator brushes WILL wear out at about 150kmi.


Well, mine fits that description. Since the existing belt has some cracks I had purchased a replacement and was getting ready to put it in. Now I am wondering what else I should look at buying prior to taking this apart. Tensioner? Pulley? Shock? I really don't want to have the car out of service for a couple of days while parts come.

Anyone have experience with the most likely candidate for failure, or what I should look for before disassembly/ordering?

thank (again)




The lifters will clatter from time to time. The engines "like" synthetic oil and it WILL reduce "lifter" clatter. I use either Mobil 1 or Mobil Delvac 1.

August M. Booth, Jr. Ph.D.

If the tensioner pulley is at an angle, replace it. It will go on for a time, but the belt will start to squeak -- well before breaking.

While you are doing it, replace the damper (not the spring) that attaches the tensioner to the head.

This is about all, the rest of the system is quite robust.

My 602 has the same problem. It's been 10k+ miles since I noticed it. I thought that I would fix it at the same time I replace the front crank seal. What part do I actually need to replace?

Fastlane shows part G6002-32871, called Acc. Belt Tension Adj. Is this the part I need to replace?

here's what I went with
 

For starters, I ordered

G6020-24744 the Acc belt idler pulley
G6003-35757 ... damper
plus I think I ordered a bolt


But as I was looking at it last night. It looked like the deflection in the system was at the base of piece that looked like the 6002-32871 Acc. Belt Tension Adj (the picture looks the same).

I will take it apart when the parts arrive. I may be doing an overnight order, we will see.

Let me know if you want a pic to compare the angle to yours.

alec

There are also 2 black plastic dust covers that you should get. They snap onto the front of the adjuster and the pulley over the bolt holes. Also replace the pulley while you have it out. Shouldnt take too long, 1-2 hours. Hardest part for me was removing the cooling fan bolt, its tight access.

I get the fan bolt off, I used the insert of an allen socket with a closed end wench and a cheater bar slipped over the wrench.

I got it done...
 

The dust caps were a good call, the old one on the tensioner shattered on removal.

I don't know if I needed to, but I removed the radiator to get more working room. It wasn't really that tough, plus I got to replace the coolant with MB orange. Some of the bolts were pretty frozen, but the PB buster came through.

The bearings on the tensioner were really pretty fried- lots of grinding and play. The pulley itself had only a minimum of play, but the running surface was scored.

All in all I felt like superman.

Which part was bad? Was it the pully...

Or the tension assembly?

bad parts
 

The tensioner assembly was much worse, and probably would have failed within 5000 miles.

The pulley was not too bad at all, but would have needed replacement within the next 5years....

Thanks, I'll order them as soon as I send this.

make sure and get some liquid wrench
 

make sure and get some liquid wrench or PB buster. There are a lot of bolts on mine that were frozen or close to it. Without the thread loosener, I think it would have taken me twice as long.

Belt Tensioner bad
 

Thought I'd post a pic; although I imagine it's pretty obvious if you see it - one of those "what the heck!!" moments.

http://www.peachparts.com/shopforum/...1&d=1501358701

I started hearing a noise and thought - "that sounds like a loose belt". So I checked and the tension was fine. I kept driving it, and decided it it was more of a squeak than a squeal. Finally took the belt off to inspect it - I did notice that it wasn't riding in the center of the tensioner pulley. Once I got it off it was obvious. After unbolting the shock there was tons of play in the tensioner bearing and with a mirror I could see the balls in the bearing - that can't be right. In the picture you can see that the tensioner bolt is offset in the tensioner.

The tensioner bolt is bigger than a 10mm allen, I read in another another thread that it is 12mm - can anyone confirm that for a 603.971?
And does anyone recall if it is a right or left hand thread??

I got the tensioner pulley off (6mm allen) and it's fine. Turned everything else by hand and they seemed smooth, no noticeable noise, and no play. Shock and all the other bits and pieces alook fine.

EPC says I have either the second or third version in this diagram
http://www.peachparts.com/shopforum/...1&d=1501359461

Looks like it will be easier to replace the tensioner if the fan clutch comes off (my repair manual says to take it off) and I've been thinking about replacing the fan clutch and the water pump so i think those will be on the list too.
.
And of course, after seeing the state of the tensioner - I probably shouldn't have been driving it. Hope it is just the tensioner.

Replace the pulley as well as the tensioner. If you're ordering frim a Mercedes dealer, get the plastic 'hubcaps' for the pulley and the tensioner bearing. Odds are good that you will break one or both taking them off. Finally, replace the shock while you're in there.

Oh, forgot. All the threads involved are regular right hand. 10mm sounds right for the tensioner, but it's been a while.