Vibration - Motor mount and/or Timing belt question
08-21-2017, 03:00 PM
#1
5th Gear
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Vibration - Motor mount and/or Timing belt question
I picked up an 86 944 NA a few weeks back. It had a little bit of a rough idle, but not that bad. I had the belt and pump done about three weeks ago for safety. Since then (150 miles) the vibration at idle has gotten much, much worse. Will the motor mounts degrade that rapidly or could it be something related to the timing belt job. I'm not new to cars by any stretch but I am new to Porsches. Any help would be greatly appreciated.
Mike
Mike
08-21-2017, 03:30 PM
#2
Track Day
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If the balance shaft keys where put back on wrong during the timing belt change, that could explain why vibration got worse. I know mine were installed wrong by a PO and it was a very shaky idle.
Excerpt from clarks garage http://www.clarks-garage.com/shop-manual/eng-06.htm:
5.Align the upper balance shaft so that the notch on the edge of the sprocket aligns with the notch in the rear timing cover. It is located at approximately the 1 o'clock position.
6.Align the lower balance shaft so that the notch on the edge of the sprocket aligns with the raised tab which is molded into the rear timing cover. It is located at approximately the 7 o'clock position.
Excerpt from clarks garage http://www.clarks-garage.com/shop-manual/eng-06.htm:
5.Align the upper balance shaft so that the notch on the edge of the sprocket aligns with the notch in the rear timing cover. It is located at approximately the 1 o'clock position.
6.Align the lower balance shaft so that the notch on the edge of the sprocket aligns with the raised tab which is molded into the rear timing cover. It is located at approximately the 7 o'clock position.
08-21-2017, 03:31 PM
#3
Rainman
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balance belts tend to show around 3000rpm and higher if they are misaligned, though i suppose it'd be possible to really misalign them to move the vibration rpm around significantly.
general rule of 944 vibrations:
idle - engine not running right, or motor mounts
2000rpm range - exhaust rubber donut mounts
3000rpm+ buzzing = balance shafts
general rule of 944 vibrations:
idle - engine not running right, or motor mounts
2000rpm range - exhaust rubber donut mounts
3000rpm+ buzzing = balance shafts
08-21-2017, 06:55 PM
#4
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Did the vibration at idle start immediately after the timing belt work or did it gradually get worse. Regardless, I'd guess that if it is only at idle it is the engine mounts. Do you hit any vibration or resonance above 3000rpm or so... if so, then they probably did not align the balance shaft belts.
After I got my 944, I had a bad 4000rpm vibe and idle vibe. Balance shaft alignment took care of the 4000, engine mounts took care of the idle. Huge difference in the enjoyment of the car.
Good luck.
After I got my 944, I had a bad 4000rpm vibe and idle vibe. Balance shaft alignment took care of the 4000, engine mounts took care of the idle. Huge difference in the enjoyment of the car.
Good luck.
08-21-2017, 10:31 PM
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The vibration has got progressively worse after the belt. That said, I may have 20 miles on it before the belt job. It seems that over the last 50-60 miles it has got much worse. Almost not drivable. I don't notice much of any vibration of idle. It
08-22-2017, 09:27 PM
#6
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Vibration due to out-of-sync balance shafts shouldn't really change over time, to me that would suggest a failed motor mount or two. It's entirely possible for them to go from fine to complete failure over a relatively short time. Once the damping fluid escapes, the mount collapses and does little to control vibration.