Two days ago I changed the acc. dr. belt on a friends '92 300E. The two piece fan shroud came off without problem and we had the fan hub holding tool, so no problem removing the fan. Loosening the 19 mm lock bolt and slackening the 13 mm tensioning belt allowed the belt to be removed but the pointer appeared to not move "down the ramp" but the other way. After installing and putting what seemed to be similar to sllightly more tension than the old belt had, the pointer was not at the top of the ramp, but I was able to move it with my finger. It "ratchets" in small increments, which made me wonder what purpose it serves if it can be set in any arbitrary position.

So I tried to do the same on my car (The pointer was at the top of the ramp) and sure enough, I could "rachet" it in both directions - click - click - click.

The pulley bearing on the 300E spun smoothly and had no play, but the photo of the tensioner in the Fastlane catalog shows what appears to be a rubber sleeve bushing between inner and outer hubs centered on the pivot/lock bolt, and previous threads indicate that if the rubber deteriorates, belt tension cannot be properly set and the belt may squeal.

When we fired up the engine with the new belt it ran straight and smooth and seemed to be quieter than the old belt, but the owner reported that the belt squealed for a couple of seconds on the next morning's cold start.

Question: Is there any way to inspect the rubber sleeve without removing the tensioner? I sure couldn't see it, but 20/20 hindsight says I should have tried to wiggle the tensioner pulley fore/aft and if it was sloppy with little resistance to movement, the sleeve is probably deteriorated.

Even with the Fastlane catalog picture, the M103 engine manual procedure for changing the belt and the tensioner, and the IPB, it's tough to figure out the design architecture - particularly the pointer. Like the throttle linkage, it appears to be more complex than necessary, and boy that tensioner ain't cheap!

With the shroud off it was no problem getting the 8 mm hex socket onto the fan hub bolt on the 300E, but when I looked at my 190E 2.6 there appears to be less clearance between the front of the fan and radiator - maybe not enough to get the 3/8" drive 8 mm hex on a breaker bar onto the bolt??? Anyone tried this on a 190E 2.6?

Duke

The car is 13 years old! You don't say how many miles. I have had this problem on three 300E's. The heat gets to the rubber. They are OK until you try to adjust it, then they fail. So they cost what $150 divided by 13 years equals about 12 bucks a year. At least that's how I look at it.

Buy a replacement and replace the adjustment rod and nut. Also replace the belt tensioner shock. Should be good or another 150K.

Steve

As far as room I use a 3/8 ratchet and allen socket, break it loose a couple of turns then barly get it out and use a allen wrench or just the socket to get the bolt out, pretty tight

Are you referring to a 190E 2.6 or a 300E?

This 300E only has about 35K miles.

For anyone who has replaced the tensioner, what was the problem with the old one. Was the rubber bushing deteriorated or was the pulley bearing bad?

Duke

I've got all the 103 engine manual pdfs that are part of the 201 documentation from http//mb.braingears.com. Group 13 drive belt shows the tensioner type with graduations, and step 8 calls for setting the pointer at the first graduation mark prior to fitting the new belt, so this implies that the pointer can be moved as required, and you have to have it at the correct beginning mark to achieve proper tension depending on the accessory configuration - which is specified as the 7th with A/C compressor (fifth without).

However there is no reference to the ramp type tensioner and where to position the pointer prior to tensioning.

I tried to look up a procedure in the 124 disk set and there is no group 13 that is part of the engine manual. Did I miss somethilng? There is a group 13 on the 126 disk set for a 300SE, but the sheets are the same as the 103 manual that's part of the 201 documents.

Has anyone seen a procedure that describes tensioning the belt with the "ramp type" tension scale?

Duke