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Dear Fellow Brickboarders,
May this find you well. My nephew and I recently replaced the timing belt &
tensioner / seals / water pump / harmonic balancer on his '90 760 turbo
(with B230F).
We came upon only one issue, that seems not to be addressed in the FAQs.
That issue: how to ensure that the keyway in the harmonic balancer
engages the key on the crank sprocket. Because the harmonic balancer's
keyway is "blind" - i.e., it does not run from the rear face all the way through to the front face - there is no obvious way to ensure perfect alignment of the keyway with the key, before tapping the balancer into place.
I presume the keyway is "blind" (i.e., not machined all the way from back face to front face), to keep water away from the crank sprocket.
Still, it is critically important properly to seat the balancer on the crank sprocket. This leads me to ask whether it would be feasible to drill a "sight hole" through the front face of the balancer (into the key way), through which one could check the balancer keyway-crank sprocket key alignment, before seating the balancer?
Once the balancer had been seated, the "sight hole" could be plugged with grease or even a small piece of rubber. Because this plug is close to the shaft, I do not think it would "unbalance" the balancer.
It seems clear that if the balancer is not seated into the crank sprocket key, the balancer will rotate on the crankshaft, likely scoring the crankshaft and producing many of the symptoms of a failed balancer. Moreover, if the balancer is not aligned properly, and then "seated" it could damage the crank sprocket, which I gather costs about $100 to replace.
I recognize that drilling through the balancer's face - to create a seating "sight hole" - raises the risk of water penetration and corrosion, and also the possibly (likely slight) of creating stress cracks in the balancer.
What suggestions do you have?
Yours faithfully,
spook
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