New engine vibration
07-19-2009, 10:19 PM
#1
Racer
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New engine vibration
Just got the car back after having all of the "front of the motor" stuff (belts, rollers, water pump, etc.) this past Friday. Autocrossed today - no temp related issues, so all appears to be well. But, the engine now has a hard edged buzz starting at 3500-4000 rpm. I can feel it through the shifter and the pedals. Balance shaft off by a tooth? Thoughts....
07-20-2009, 01:22 AM
#2
Three Wheelin'
i'd say that would be the first place to look...did you have the work done by a shop? The balance shaft could've been put 180 degrees out of phase, or it could be just a little off...other than that there shouldn't really be much else that could be done wrong...just make sure you check the tensioners and make sure one of them isn't ready to fall off!
07-20-2009, 09:16 AM
#3
Racer
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Yes, it was done by an independent shop. The shop owner is a former 944/951 owner, but I think one of his minions actualy did the work (he was out on vacation when I picked up the car). Sounds like a trip back...argh!
07-20-2009, 10:06 AM
#4
Race Car
07-21-2009, 12:09 AM
#5
Rennlist Member
Sounds like the situation warned about in Clark's; the BS pulleys are stamped "O" but only the upper gets mounted that way.
http://clarks-garage.com/pdf-manual/eng-08.pdf
http://clarks-garage.com/pdf-manual/eng-08.pdf
07-21-2009, 03:38 PM
#6
Race Director
Yep balance shaft 180 deg out of phase. Very easy mistake to make even if you know what you are doing. Usally you only do it once since you remember that you need to double check each time after rather than just putting it on. Don't go too long with it wrong as can cause all kind of parts to break.
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08-03-2009, 09:51 PM
#8
Racer
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Update. Got the car back today and all is well. Sure 'nuff, one of the balance shafts was 180 degrees out. Original mechanic faught with the shop owner about it - "...can't be..." - and is no longer employed there.
08-04-2009, 12:01 AM
#9
Rennlist Member
That's dumb to quit or get fired over something like that; no one knows everything, everyone makes mistakes.
08-04-2009, 09:06 AM
#10
Race Car
08-04-2009, 11:42 AM
#11
Nordschleife Master
It is an easy mistake to make, but you would know something was wrong on the test drive unless you had zero experience on 944's and thought they all sounded like that. In which case they shouldn't be doing the belts in the first place.
I hate paying mechanics to learn about my car!
I hate paying mechanics to learn about my car!
