Engine counter-rotation breaks camshaft

Louis A. Mulieri mulieri at physiology.med.uvm.edu
Fri Mar 29 13:36:53 EST 2002

Hi Guys,
	There can be another prohibition to reversing engine
rotation: Timing chain :-(. I had a 190 Mercedes and during installation
of new rod bearings I unknowingly did a no-no. Turned the flywheel
backwards by hand to rotate the crankshaft from underneath. Finished the
job beautifully and then heard some terrible noises on first crank. No
start...no compression....terrible. Took off valve cover to find overhead
camshaft broken in two. The the timing chain tensioner only takes up
slack between crankshaft and cam gears with CW rotation. Turn the other
way and the chain slackens on the opposite sides of the gears where there
is no tensioner. This allows the chain to jump some teeth. Maybe this is
no longer a problem with timing belts???


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