My 92 400E has belt squeal, and I adjusted the tensioner (after loosening the center bolt!) and put the (new, was missing!) pointer between the center two lines, but it still squeals.

Pullling the tensioner, the adjuster plate flats have worn into the tensioner shaft flats, so I tried flipping the adjuster plate over and swapping its location onto an unworn position on the shaft flats. Still squeals.

This is a terrible design. The manual shows two later configuration tensioners, one of which the catalog shows applicable to later engines than mine, but it includes a note that if installed on earlier engines, you need two additional little pieces. This implies a retrofit is possible.

Has anyone retrofitted the later config tensioner? It looks totally different. How does it mount? Are other hardware needed to mount it? Do you just swap the pulley itself over?

Any comments/help would be greatly appreciated! (Please cc me directly with any responses, as I may not have access here from work!)

Gerry Visel
gcvisel@gmail.com

I pulled the old one, and, in addition to the wear on the shaft flats, it is shot inside. I did the inspection by putting it in a vise on the flats and trying to turn it 30 degrees to see that it would spring back. It turned freely past 30 degrees.

Being the engineer, I pulled the snap rings off the end and tapped on the shaft, and one of the end "bearings" popped out, and I could see that the internal rubber piece was sheared.

Why do the MB engineers rely so much on rubber for shock isolation? Isn't there a better way???

Gerry

I'm going to chime in here and declare a pox on everyone who had a hand in the design of the belt tensioner on my '90 300E. If the tensioner goes out on either of my 150K plus miles GM products, I purchase a new one at nearly any parts store for what I think is a reasonable price and spend about 15 min (with NO removal of any other part required) installing it. When it went out on the Benz last week I spent nearly $200 for the tensioner and dampener (my adjuster rod was in good shape) and then went through about a 2.5-3 hour ordeal that included removing the radiator, the water pump pulley, the power steering pump pulley, the fan pulley and the bracket that holds the tensioner in place. Of course after all the removal of parts, installing the tensioner itself is like putting panty hose on a bobcat and then the aforementioned parts have to be reinstalled and the cooling system refilled. I love my Benz and truly believe it is a driving experience like no other but no sane person can think that this is the best (or even a good) way to run an accessory belt system!

Hi,

at what mileage should I be concerned about this (92 400E at 170K miles)
Is it a preventive maintenance item, or just wait for the squealing?

Thanks.

I'm about to get the timing chain/tensioner and upper/mid chain rails replaced, is this a good time to do the belt tensioner as well, based on the deconstruction?