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Harmonic balancer delamination, how to verify on V12?

XJ40 ( XJ81 ) 1986 - 1994

Harmonic balancer delamination, how to verify on V12?

Old 06-20-2018, 08:50 PM
al_roethlisberger's Avatar
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Question Harmonic balancer delamination, how to verify on V12?

On the AJ16 engine one can simply paint a white stripe across the pulleys and onto the crankshaft position sensor toothed ring and if that line becomes misaligned then that startup squeal is the harmonic balancer delaminating and not a slipping belt.

For the V12 is there a similar easy test to verify if my startup squeal is the harmonic balancer (I suspect it is) or one of the four belts slipping?

You might think it would be easy to tell from just putting one's head near the front of the engine and revving the throttle, but the squealing sound bounces around such that it is hard to pinpoint.

If it is the harmonic balancer, do we recommend the same "starter bump" method to break the crankshaft bolt loose as on the X305 V12 and X300 AJ16? If so, what's the correct size socket for the crank bolt on the XJ40 V12?

Old 06-30-2018, 07:00 PM
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Hi Al,

Sorry for the late reply. I haven't tried this, but I assume you could paint a line across the damper and the pulley and watch for misalignment to develop between the inner rim of the damper and the rest of the damper and pulley. The damper is part 12 and the pulley is part 17, which bolts to the damper:



Last edited by Don B; 06-30-2018 at 07:03 PM.
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