balance shaft failure

[philth]

Anyone ever heard of the bolts that secure the balance shaft shearing off and causing a catastophic engine failure?

[Wayne 962]

No, has this happened to you? The balance shafts in an engine counter the motion of the pistons and reduce vibration. If they are 'out of balance' then they will do the opposite and create harmonic motions and resonate at certain RPM. This can result in catastrophic failure, but it's very rare...

-Wayne

[philth]

Wayne,

Thanks for your response. I broght my girls 01 10k mi Boxter to the dealer for an oil service and to repair a leaky rear main and I got a bad phone call..."has anyone else serviced this car?"
"no, why?"
"We got in there and found that 2 of the 4 bolts that hold the balance shaft in place were nearly completely sheared off. You were about 15 miles away from a complete engine failure"
"What the f....??"
"We've never seen this before. We're gonna keep the car and tear the motor down to 1) try and find out why this may have happened and 2) ensure that there are no metal bits floating around in there. If there are, we'll get you a new motor. We don't mess around with this sort of thing"

So, I'm now thinking to myself....this sounds bad. I'm not sure that I feel good about having a car like this that is nearly new with an engine that has had this sort of failure and has been completely torn down, cases split etc. Highly trained technicians aside, it seems they ought to put a new motor in...which would be likely less expensive anyhow. We're talking about hundred of hours of shop labor....not on my dime of course.

What are your thoughts.

thanks.

[Paul T]

There's a balance shaft in the boxster motor?? I thought flat sixes were pretty much an inherently balanced design with no need for counter-rotating balance shafts. When I think balance shafts I think big bore straight 4's, ala 944.