Diesel Engine Front Crank Bolt Failure and Loss of Pulleys

Pay attention! This is very common and can happen to you if you own a 1968 to 1985 diesel

This one is becoming more common than I would like to admit. It even happened to my daughter Kaias 300 TD wagon. The old 616 and 617 diesel engines produce a lot of shake and vibration and over time that can loosen the front crank bolt. Hard to believe since that big bolt it torqued to over 250 ft. pounds. If caught early enough you can save yourself a lot of grief. If it happens on the freeway (as it did with Kaia) the pulleys can fly off- you will immediately lose your power steering, the dash warning lights will come on and the engine will start to overheat! I would recommend you check the tightness of this bolt at your next service. Certainly check it at the first sign of any strange front engine clicking or clanking noise. Ignore this and I guarantee you will be sorry.

Problem & Solution

Common among these chassis:

One customer recently wrote this:

 On my 1985 300SD, I started to use your kits and directions to replace the
valve stem seals and adjust the vale clearances. Going by the steps, when I
brought the timing mark on the crank to 0, the #1 intake lobe was till on
the rocker a wee bit. When I bring it around another 180, the exhaust lobe
is pressing its rocker in also. In your booklets you say the exhaust lobe
should point to the driver side and the intake lobe should point to the
passenger side and up about 30 degrees. My intake lobe is pointing to the
passenger side but down on the rocker about 10 degrees and the exhaust lobe
points almost straight up. It seems my engine is out of time, but I don't
want to risk damaging anything. Is it possible that the crank pulley is out of
position? The engine was driving prior to disassembly, though it clearly
needed work. Please help me with my engine. I love this car and want to
drive it again! Thanks!

 This was my reply:

 Hi Ed, in that case it is highly likely the counter balancer on the end of the crank shaft has shifted.  This could either be caused by sheered off alignment pins or improper installation at some time in the past. It could be that the front crank bolt loosened up (quite common) and someone tightened it back down without checking alignment. There are two small round pins on the end of the crank that are designed to sheer off to prevent damage to the crank.

WARNING: The front pulleys and counter balance will need to be removed to inspect for this. Instructions on how to do this are contained in my front crank seal replacement kit (you would want to replace the front crank seal anyway while you are in there).

 For reference rotate the engine to bring the cam lobes into the proper position (as shown in timing chain instructions) with the marks on the cam washer and front cam tower also in alignment (this will indicate no. 1 piston is near TDC on compression stroke). You MUST do this BEFORE you remove the crank counter balancer. This gives you the engine position you will need to properly check and reinstall the counter balance pulley.