[bbranch]

Sometime during my 50 mile drive home tonight, my car started a slight vibration very similar to how it ran without the balance belt. I pulled the upper cover and inspected the belt, turned the engine over and looked for missing or broken teeth and found nothing amiss. The belt gets fairly tight when turning it 90 degrees over the long stretch from the lower to upper balance shafts. Belts, rollers and tensioners were all replaced about 12K miles ago and the belts were retentioned at 3K miles after installation. Is it possible for a fairly close to proper tension belt to skip a tooth? Any other ideas for what would introduce a vibration during a normal drive home? You can feel it through the clutch in particular, and it makes a louder exhaust note, I can't hear the belt whine nearly as well...



Any help appreciated. :-)



-Brett

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[NeedPorscheSpeed]

Although you almost certainly have already checked this, but...



are your balance shaft sprockets lined up with the marks on the rear belt cover?



Best of luck!

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[Greimann]

Maybe a collapsed motor mount. Once they go, the normal engine vibration is amplified through the chassis.

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[rustech]

[quote name='bbranch' date='May 14 2005, 12:41 AM']You can feel it through the clutch in particular, and it makes a louder exhaust note, I can't hear the belt whine nearly as well...



Any help appreciated. :-)



-Brett

[right][post="4730"]<{POST_SNAPBACK}>[/post][/right][/quote]



Although it seems as though your belt is tensioned properly, I think your belt did skip a bit. Since there is an obvious vibration with limited causes, the thing that gives it away to me is the changed exhaust note. When the balances shaft(s) are out, it can cause the exhaust to sound louder and more coarse. I would definately get in there and check the alignment of the shafts. You should have some belt whine at cold starts when properly tensioned.

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[bbranch]

After going back into it again, I retract my statement about it getting tight after turning 90 degrees. Maybe. <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" /> Is it supposed to be hard to twist it 90 degrees, or is that point that you just *start* to get any tension on it? I think I could pretty easily twist it 180 degrees if I wanted to exercise my fingers.

FYI - it did skip. I lined up the TDC mark on the cam shaft and the top balance shaft lines up, but looking through the little round hole, I can't find the notch in the lower balance shaft sprocket at all. Since I don't have a flywheel lock, I had had the belts done by a shop (9K miles ago), so hopefully they will cover resetting and retensioning on their dime. Should I push for a new belt (presuming that this one still has all its teeth and they don't automatically replace it)?



-Brett

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