Been surfing the site and can't really find my answer.

I replaced my alternator last weekend, no problem there....but the belt tensioner threw me off a little. I have the adjuster nut behind the reservoir (more on this later) however I saw no nut on the tensioner pulley, mine had a plastic cover on it. I removed it and had to use a 8mm hex socket/wrench fit into the pulley to lever it back an inch or so so I could get the belt off/on. Had to hold tension on it while pulling belt on/off..lotsa fun! There was no bolt that I could see. Loosening the adjustor nut didn't seem to help any at all. I also didn't see any tension indicators on the pulley.

When I managed to get belt back on, tightened down the adjustor a tad too much, yep it popped. However, the belt is still pretty tight because of the pulley.

My question is could I have a new type of tensioner on my car (I bought it used)and if so am I hurting anything by driving it w/ out the adjustor bolt? Also what do I need to replace to get the adjustor bolt back into play, I assume I broke whatever it was attached to. Thanks!



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88 300E (plus used to have 72 350SL, 83 240D)
Dad's got a 99 ML320 & 93 300SE...we're a Mercedes family !

I read this three times before it finally dawned on me what the problem was. The nut you are trying to use to "lever" with is not the one you should be messing with. The big one (19mm) in the center of the tensioner assy is the one that has to be loosened for any adjusting to take place. If you don't loosen this fella first, you're gonna break the whole thing into junkland. Sounds like you ought to replace the whole tensioner assy and start over..BTW, the pointer for the tensioner adjustment is not on the pulley, it's on the front of the tensioner body behind that big bolt..
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Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE

[This message has been edited by jeffsr (edited 11-09-2000).]

Thanks. That helps. What I get for following the British Haynes manual!...Between the site and my performance products catalog I have figured out that I need to replace the tensioner adjuster screw assembly as I snapped the collar its attached to which in turn attaches to the tensioner....fun fun.

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88 300E (plus used to have 72 350SL, 83 240D)
Dad's got a 99 ML320 & 93 300SE...we're a Mercedes family !

I had a similar problem with my 88 300E as the tensioner adjustment was stripped and did not work. It is not easy to see the 19mm bolt that locks the tensioner down. It is located between the tensioner body and the power stearing pump pulley. It may be covered with grime if your car leaks like mine did. You
will have to remove the tensioner if the threaded rod is damaged but can sneak a new nut in there with a lot of work if you want to. It is easier to see what you are doing and access to the bolt is better with the
fan and shroud off. While fixing mine I found the crankshaft pulley bolt loose, removed it with my fingers. So you might want to check that out too. I have a Technibook manual and it is not too good in that area either.

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Dave
88 300E 130K

Don't loosen up the center bolt until you have all of the parts needed. You are safe for now. The rod and nut that snapped are for tensioning only, not for HOLDING the tension. That is the job of the big pinch bolt in the middle.

Your problem is going to be if you take out the tensioner to replace the rod and nut and the tensioner is marginal. You will have to replace it soon if so.

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Benzmac:
Donnie Drummonds
300E
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM
OWNER OF MB AUTOWERKS .COM

Our 300E (W124) needs the belt replaced. I would call this a serpentine belt and I already went through the 'break it' mode on my Chevy truck. But now I understand how that one works so it only takes a few minutes- with a socket & a torque wrench.

For the 1987 300E Now, I have the Technibooks Owners Workshop Manual for this 300E and the diagram does not match what I'm looking at. So I diagrammed it to minimize the duh with the belt going back on BUT - the pulley where I think they show the tensioner has a smooth cap- no nut.
It also looks like I need to pull the fan shroud and maybe other stuff also. Can someone tell me where I can look for a better description. It 'looks like' I could easily break something more expensive than last time.

Sure appreciate forums like this,
TallTrees
(on the Left Coast)

yep, look at your diagram, no; look at your tensioner pulley, attach to it is the tensioner,,,round rubber, etc. There should be a big #$# nut in the center of it. If you have a cap there, I'm sure there's a nut. Granted, your car is not the same as mine but it's around the same year.

You got to loosen that nut about 1/2 turn. 19MM big nut and hard to turn, i use a pipe extension and it's real easy then. I do this from under the car. Once that nut is loose, then loosen the adjusting screw 13mm enough to get belt off.
Caution; read manual and notice where your "pointer is" that's where you want to get to after belt replacement.

1. 19mm- first
2. 13mm -second

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JHaburay

1972 280se 4.5 "princess"
1986 2.3-16v first 100 (099) USA

I appreciate the comments. Thank You. btw- the 'pointer' in the diagram you mention is out at the end of the Spanner wrench showing that 'just' putting a spanner wrench for Outer Trox bolt E10 (socket into pulley) on it and pulling up will release the tension.

Because the Previous Owner say motor was rebuilt, I even wnder if it is the same as the year the car was built. I'll look around there tomorrow with a 19mm & a 13mm handy. Thanks,
tt

The pointer is the little plastic triangle on the front of the tensioner, by the 19mm bolt.

You'll have to pull the fan shroud and the fan using an 8mm allen and a retaining rod to hold the clutch.

Loosen the 19mm bolt.

Untension the tensioner at the 13mm adjusting nut.

Pull off the belt. Spin the pulleys and check the bearings for noise or roughness.

Install is the reverse. Make sure you reset the pointer at the low end of the triangle (right side), and tension til it hits the peak of the triangle (left side).