camshaft jump - PeachParts Mercedes-Benz Forum

longshot · #1 09-28-2006, 09:40 PM

I have an '83 300D
while driving along; I heard a lot of noise. I stopped, opened hood and saw the valve cover (over timing chain) had a split in case.
the engine ran until I shut it off (quickly).
After removing valve cover; I discovered the chain looks fine; but forward 2 cam towers have splits in them. Chain is very tight and tensioner looks to be fine.
Anybody have an idea what made cam towers break? There is 191K miles on vehicle?!!
Thanks!

TheDon · #2 09-28-2006, 09:41 PM

the timing chain jumped and screwed up the timing, making the cylinder hit the valves and force the cam up and break the towers... thats my guess

dkveuro · #3 09-28-2006, 10:01 PM

Fatigue and overtighened fasteners.
Just fixed a 240D that did just that.

Timing was okay but it broke nearly every rocker tower.
This engine had lost it's vacuum pump roller that caused the towers to break.

Dropped the oil pan...replaced the vac' pump and cam/towers assembly...been back in service for 3 weeks now.

Although jumped timing will do this, it usually bends the valves too.

.

longshot · #4 09-28-2006, 11:02 PM

I am no expert; but I do not think that the timing jumped, or bent the valves because the engine was still running when I shut it off--wouldn't the engine have quit if the timing jumped and the valves bent??

Lostyankee · #5 09-28-2006, 11:08 PM

Do a manual compression check with all injectors removed. If you feel any resistance as in piston hitting a valve, stop! This doesn't have to be a fancy test just a finger over the hole should tell you enough to procede further.

#6 09-28-2006, 11:16 PM

You already have the valve cover off, turn it by hand until the cam marks line up. You will be able to find out right away if it did indeed skip a link.

longshot · #7 09-30-2006, 02:04 PM

Quote:

Originally Posted by Lostyankee

Do a manual compression check with all injectors removed. If you feel any resistance as in piston hitting a valve, stop! This doesn't have to be a fancy test just a finger over the hole should tell you enough to procede further.

Lostyankee,
I removed the injectors and rotated crank till cam marks are aligned; looks like it is about 35 degrees off from crank! Is it possible the valves are OK, or are they bent for sure? Thanks!