What causes engine vibrations?
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From: Overland Park Kansas
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What causes engine vibrations?
I've had two vehicle in a row with this problem. The first I bought, then sold because I was worried the engine wasn't properly balanced from the factory. Now, I REALLy want another vehicle (3.5L V6 Vehicross) that also has this problem.
My 383 builder assured me engines only vibrate from balance issues -- not impending failure. Short block failures are seen as rod-knocks (or worse) according to him.
Both the Vehicross and Jeep GC (before that) had this SAME problem. Both had a vibration peaking near 2500 rpms that made hwy driving quite annoying. Vibration in the interior caused resonance that --felt-- like wheel/diff bearing problems. Neither had that problem though. Both vehicles exhibited the same vibration at a stop -- in park. It was coming from their motor(s).
This is clearly an engine vibration issue. Do you think its most likely a motor mount problem in both vehicles? Or balance issues? Or something else? If so, what?
P.S. How much vibration do you think a good motor really has? If it weren't for the damping of a motor mount, would it be horrible inside? Can a motor mount be "bad", transmit significant vibration, but still appear to be functioning otherwise?
My 383 builder assured me engines only vibrate from balance issues -- not impending failure. Short block failures are seen as rod-knocks (or worse) according to him.
Both the Vehicross and Jeep GC (before that) had this SAME problem. Both had a vibration peaking near 2500 rpms that made hwy driving quite annoying. Vibration in the interior caused resonance that --felt-- like wheel/diff bearing problems. Neither had that problem though. Both vehicles exhibited the same vibration at a stop -- in park. It was coming from their motor(s).
This is clearly an engine vibration issue. Do you think its most likely a motor mount problem in both vehicles? Or balance issues? Or something else? If so, what?
P.S. How much vibration do you think a good motor really has? If it weren't for the damping of a motor mount, would it be horrible inside? Can a motor mount be "bad", transmit significant vibration, but still appear to be functioning otherwise?
Last edited by GREGGPENN; May 26, 2010 at 10:29 PM.
Thread Starter
Race Director
Joined: Nov 2003
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From: Overland Park Kansas
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How common is an out-of-balance FACTORY motor? (Since the vehicle were in the 98-2001 era, take that into consideration for your answer.)
How harmful is an out-of-balance motor? If one creates a harmonic vibration at certain frequency(s), can it still live a normal life?
Should I suspect the harmonic balancer? Can it appear O.K. but be internally shifted?
(I'm don't know about the 2001 3.5L V6 Isuzu, but the Jeep was an internally balanced motor.)
How harmful is an out-of-balance motor? If one creates a harmonic vibration at certain frequency(s), can it still live a normal life?
Should I suspect the harmonic balancer? Can it appear O.K. but be internally shifted?
(I'm don't know about the 2001 3.5L V6 Isuzu, but the Jeep was an internally balanced motor.)
Melting Slicks
Joined: Apr 2003
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From: Red Sox Nation! RI
Given that the simplest answer is often the right one, I'd be guessing at a motor mount. I would think an out of balance, stock motor would be pretty rare. But 2?? Both automatics? That's just my guess.
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How much/little vibration can a harmonic balancer make on an internal balanaced motor? Are there really any concentrated weights that change if the weight balancer actually "debonds" or rotates? Does any delamination cause the balancer to wobble -- even on a small scale?
Now that I think about it, I'm thinking my builder said failed balancers cause significant vibration. What I'm asking about is like the difference between holding a lawn mower with a bare metal handle vs one with dense foam padding. (Where the car in question feels like a lawn mower vibrating vs a Cadillac.)
I'm not talking about clutch-chatter-like vibration.
Now that I think about it, I'm thinking my builder said failed balancers cause significant vibration. What I'm asking about is like the difference between holding a lawn mower with a bare metal handle vs one with dense foam padding. (Where the car in question feels like a lawn mower vibrating vs a Cadillac.)
I'm not talking about clutch-chatter-like vibration.
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From: Sandhills of North Carolina
How much/little vibration can a harmonic balancer make on an internal balanaced motor? Are there really any concentrated weights that change if the weight balancer actually "debonds" or rotates? Does any delamination cause the balancer to wobble -- even on a small scale?.
Thread Starter
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From: Overland Park Kansas
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They were (are) both automatics. Both were $30k SUVs when made. I'm pretty sure eBay wasn't involved. I'm also thinking flexplates for an internally balanced motor would be neutral balanced themselves.
Melting Slicks
Joined: Mar 2002
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From: S.L.C. UT
Anything on the engine touching the body can cause a vibration, with no rubber between them. Exhaust, motor mounts, ect. The motor mounts would have to be bad enough that it was metal to metal. Or a trans mount, but that doesn't really apply to our cars.
Unless it's a internal engine problem.
One other thing you can go do to diagnoise vibration problems is pull the serp belt and start it up and see if the vibration is still there, If it's gone, it's caused by something on the front of the engine. If it's still there it's something else. engine accessories can cause vibrations if they are bad enough.
Unless it's a internal engine problem.
One other thing you can go do to diagnoise vibration problems is pull the serp belt and start it up and see if the vibration is still there, If it's gone, it's caused by something on the front of the engine. If it's still there it's something else. engine accessories can cause vibrations if they are bad enough.
Last edited by tpi 421 vette; May 27, 2010 at 02:12 AM.
