Belt Tensioner and Combination Support
 

This weekend I replaced the hydraulic lifters in my '94 E320 (M104), a fairly involved process but not too bad as I followed closely the procedures outlined in the CD manual.

The biggest problem was the belt tensioner. Seems that the last fella who put in the NAPA serpentine belt broke the tensioning nut and over torqued the 10MM hex bolt that goes thru the center of the tensioner to compensate. When I removed the belt, I know I'd have trouble on the return trip. Well, I did. The over torque of the center bolt had caused the the Combination Support to split. The Combination Support is the aluminium thing that acts a crankcase breather and mounting support for the Pwr Steering Pump, A/C compressor and Tensioner. I was able to get it out, had to remove the Pwr Steering Pump and A/C compressor. The tough part was getting that poor mistreated tension centerbolt out.

Can't wait to call around for prices on this part (103 131 09 35). Could be $40, could be $400. What do you think?

Getting it welded may be less expensive.

Tim

Follow Up
 

I'd consider welding but my local dealership was able to get one, the only one in the country. The list price was $133. So, I'll go that route.

It's funny that the biggest problem with the hydraulic valve replacement happened to be one of the more routine maintenance procedures.

I think that these cars are very intelligently engineered. I like the challenge of working on them, very little margin of error. Each step must be performed very deliberately or small disasters can occur. I had such a tough time getting that tensioner tightening bolt out that I thought I may have to have the car towed to a repair shop. What an embarrasment and ego killer that would have been!

inetd,

The bolt thru the tensioner does not really lock though. I think it just compresses the rubber bushin inside to stop the tensioner from rotating on the mount from the pressure of the belt in its tightend state. It requires 75NM of torque to do this on a healthy tensioner, not the 140NM that stripped the threads of the Combination Mount.

If the indexing of the S-class CD is the same as the 124, try starting with "05-2110.pdf - Examining and replacing hydraulic valve clearance compensating elements (bucket tappets)." The meat of the procedure is the removal of the camshafts, "05-2200" and all things leading up to that like upper front cover removal, darining coolant, removing timing chain tensioner, etc., etc.. The lifters, or bucket tappets come out with any small suction cup.