Timing belt rode off

All,

I installed a new timing belt yesterday on my '90 240DL. Not too
complicated. I was glad I bought that special tool to hold the
crankshaft pulley. Slight problem on re-assembly.

The Haynes manual is a bit out of sequence on re-assembly. They
instruct to torque up the belt tensioner before installing/torquing the
crankshaft pulley. Problem with that is you have to have the tensioner
nut off to install that crank-holding tool to tighten the crank pulley bolt.

The next problem was my fault, I failed to re-tighten the tensioner
bolt. So, after startup, with the tensioner pulley misaligned (not
tightened down), the timing belt rode half off the camshaft pulley,
burning a neat slice through the timing belt cover in just a few
seconds. I shut it down before it rode completely off the camshaft and
intermediate (BTW, what the hell does this intermediate shaft do? Just
hold a pulley?)shaft pulleys.

So, I'll need a new timing belt cover. Duct tape won't last forever.

How about that belt, though? Does anyone think I damaged it when it
ran half-off the pulleys?

By the way, I didn't bother with the oil seals. THey weren't leaking
and looked pristine. Also, I didn't want to spend the price for the two
seal drivers and the pulley holder to do that job. Also, I left the
water pump alone. It wasn't leaking either. I know some things are
better replaced before they fail. Any comments on my choice not to fool
with those components?

 

I always tighten the crank pulley, then turn the motor over a few times
by hand slacken the tensioner nut, press the idler wheel full tight with
a long screwdriver, then tighten the nut, turn the motor over two more
times, then slacken the nut, let the belt find its tension against the
spring. retighten and cover. For some reason, whenever you take the idler
assembly off the motor (for inspection, seal replacement, whatever) you
don't always see that the pin that engages the head is cocked. Then when
the nut is tightened the belt is overtight and creeps of the end of the
cam shaft. If this seems like too much trouble, consider the expense of
not doing it on a 16, 20 or 24 valve engine with a manual tensioner.

When the red motor was a pushrod design the shaft that holds the jack
shaft pulley did three things: it was the cam shaft, and it had a gear to
turn the distributor and oil pump. With the overhead cam design all it
has to do is turn the distributor and oil pump on the 240 application. On
the 740 application with cam driven distributor it just drives the oil
pump.

Look at it if it doesn't look damaged, use it and check it fairly
frequently or if that's going to be a bother, replace it with a new one.

The crank pulley always seeps, even if the pcv system is kept pristine.
Water pumps are easy to do on a 240 and only require removing the top
half of the outer cover. You don't lose any time by doing it later.
Bob

 

On a carbureted redblock it also drives the mechanical fuel pump.