[MCL968]

My 92 has started vibrating, and I suspect one of the balance shafts is out of synch.

 

Does anyone have a step by step guide for checking them?

 

It may be the motor mounts as they are a few years old, but before I just start swapping parts, I want to check the shafts.

 

It's a very small vibration, not like an old panhead Harley going uphill on a tank of bad gas, more like a high-frequency buzz that I feel through the pedals.

 

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[Bulti]

You could start by removing the 2 plastic covers that encase the timing- and balance belt. Check if the markings of both BB sprockets lign up with the tabs on the rear half of the plastic cover. You can check the bottom one without removing the A/C belt and V-belt.


There is a thread about the motor mounts, started by KRAG50. Lots of info in there. You can measure the height of them and get an idea if they are collapsed or not.

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[netopyer]

beware,  i felt the same,  later i heard a clicking noise, and balance shaft belt was stripped off the teeth on  half of its length, and when  the first remaining tooth hit the sprocket on the balance shaft, , it made a click..  pull out airbox,  and  put down the covers,  and if you find anything  wrong with the BS belt, just cut it and pull it out, car can run without it, and you will not risk  damaging your engine by  timing belt vs balance belt interference. do it NOW

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[williamoss]

I replaced my motor mounts on my 1995 968 coupe (92,000 miles) a couple of years ago, because I felt a vibration. It was a cheaper faster fix
it than getting inside of the engine.

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[MCL968]

Thanks for the input, I will check the belts this weekend, but they were just replaced, along with the rollers, about 500 miles ago. If the shafts are set properly, I suspect I will be replacing the mounts. I have to figure out how to measure them to see if they are collapsed, but I understand there is a thread on here that tells how to do it.

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[Bulti]

It would also be wise to check if the BB still has the correct tension. A good way to do this is to try and twist the belt at the pulley of the waterpump between two fingers. You should be close to 135°. When the tension seems fine, check that the idle roller is set right in relation to the belt. The top of the idler should touch the belt, but not -or barely- deflect it. At the same time the bottom of it should stay clear 0.5 mm of the belt beneath it.


There is a picture in the manual that shows what I'm babbling about ;-). It is definitely there in one of the many threads discussing belt tension etc.

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