The car was purchased for a reduced rate as it was unable to be driven due to a problem with the crankshaft pulley. The engine would start and run, but none of the accessory belts were turning. Luckily for me, Josh had Triple-A and we got it towed to my house for free.

First, major research was done. It seems that crankshaft pulley problems are somewhat common for this type of vehicle. The following links were very helpful. Mad props to the mercedesshop.com forums.

http://www.mercedesshop.com/shopforum/showthread.php?p=115016
http://www.mercedesshop.com/shopforum/showthread.php?threadid=22647
http://www.mercedesshop.com/shopforum/showthread.php?t=141829
http://www.mercedesshop.com/shopforum/showthread.php?t=52125&


One of the forum posts mentioned something along the lines of, "The most common cause of crank pulley failure is taking your car in to have the front crank seal replaced" - meaning that the shop re-installed the crank pulley improperly which causes the pins holding it on to shear under load.

Repair:

First, the front parts of the engine were disassembled. After loosening all the accessories, removing the belts, and removing the fan and radiator hoses the crankshaft pulled was found to be loose enough to be turned by hand. The large bolt however, was very tight.

The crankshaft bolt was able to be loosened by inserting a rather large screwdriver in between the transmission vent cover and the flywheel teeth and turning the bolt with a 27MM socket.

The bolt as it came out. Missing two of the spacer washers and covered in locktite. Yikes!

The crankshaft pulley backing plate. This is what attaches to the crankshaft via the two cylindrical pins and crankshaft bolt. Notice the sheared off pin visible in the left picture. Due to the sheared off pins and obvious wear a new backing plate was obtained from Pick N Pull San Antonio.

One of the notches on the crankshaft is a bit damaged from the pins shearing off. Maybe I won't hook up the A/C.. :-(

Photo of the new backing plate being installed. The correct procedure according to the Mercedesshop Forums is to use a bass hammer to gently tap the pins into place AFTER the plate is pressed onto the crankshaft. The pin notches in th crankshaft look like they are 180 degrees apart, but they are not. The plate needs to be installed and then looked at through a mirror, it will be obvious if the notches in the crank do not line up with the holes in the plate.




Once the plate is oriented correctly on the crankshaft, it should be "pressed in" by tightening the crankshaft bolt. A good method of lining up the holes is to install the plate slightly counter-clockwise on the crank, and let the tightening of the bolt turn it slightly. Mine was still a bit off, but I was able to tap on the plate gently with a hammer to rotate it a slight amount on the crankshaft.

In Lieu of a brass hammer, the plastic handle of a screwdriver was used to prevent "mushrooming" the heads of the pins while they were pounded into place. This took a long time of very gentle tapping, have patience!

Finally, the pins are in place!

Installation is the reverse of removal..

Conclusion:

The Mercedes was put back together and has been driven approximately 250 miles with no problems. Time will tell if this problem is licked or more drastic measures need to be taken to ensure crankshaft to pulley responsibility.