cautionary timing belt tale

recently, i decided to check ignition timing on my 89 civic & noticed
the pulley wheel marks skipping about all over the place. this is
common on old cars with chain driven cams at high mileage, but on
toothed belts, this is very rare. so, finally decided to do preventive
work, including timing belt & investigate. made a highly un-nerving
discovery. the old belt had never been tensioned correctly! in fact,
it was so loose, turning the crank in reverse made the belt skip teeth!
i'd put about 14k on this car since i got it, including regular red
lines, & it had never been a problem. incredible. this is all the more
amazing because if you know what to do, properly tensioning the belt
takes less than 5 minutes. but evidently, this is was not done here.

bottom line: be careful out there folks. this could have been one
expensive way to remember to always have a used car checked when you
first get it. i knew better, but was moving house about the time i got
the car, so had other things on my mind.

how to tension the timing belt:

1. there's a 14mm bolt with it's head inside the timing belt cover about
half way down. covered by a little grommet. remove the grommet & place
ratchet in hole. unscrew bolt until it's just loose.

2. turn crank with the pulley bolt _anti-clockwise_. turn until you
reach one of the resistance points in the cycle, one where you're
resisting the cam springs.

3. tighten the tensioner bolt. the tensioner pulley is spring loaded so
tension should be correct.

if you've changed your own belt, you can be confident this works because
you've seen it in action with the covers off. of not, have faith, it
works beautifully. if you have air conditioning, you need to access
from underneath because the compressor is in the way for top access.

the problem arose because the tensioner spring is not very strong and
unless you follow book procedure & rotate the crank a few times to let
it settle & maintain tension on the "pulling" side, you get belt tension
on the "return" side & this works against the tension spring & allows
the pulling side to be slack. this then gets locked in when the
tensioner bolt is tightened.

so, job now done, but i mention it because i've seen a number of
"skipped teeth" postings here. hopefully this helps people get it right.

 

You can also tap the timing belt cover (or the bolt itself if you can reach
it) lightly once or twice with the bolt loose. This will help shock the
tensioner into climbing a bit higher on its spring, increasing tension on
the belt.

Now you just have to make sure there's a bit of slack still left in the
belt, and that there's no whining or whirring noise from the belt with the
engine running.

If the belt is now too tight, loosen that bolt again, then carefully turn
the crank _clockwise_ one or two teeth (the cams will not turn). This will
pull the tensioner back down again, and you can start over.