This is not a Barth question but hope you folks can help us. We have a 1981 Volvo that has a high frequency engine vibration that we can't seem to track down. You feel the vibration in the steering wheel and the gear shift knob. We installed new engine and transmission mounts, new exhaust system, disconnected the drive shaft, and it's still there. It's about like the kind of vibration you feel from one of those hand held vibrators to do a neck massage. Not quite that strong. It goes away mostly at certain rpms, about 2500 rpm. The vibration feels just as strong at idle as it does at any other engine speed This is a 4 cylinder fuel injected engine. My thought is the flywheel but when I first bought the car, it wasn't there. Maybe the the engine/tranny mounts made it noticeable. Thanks for your help.

quote:

The vibration feels just as strong at idle as it does at any other engine speed

Interesting that it goes away at certain RPMs, but isn't RPM dependent otherwise??? I would purchase an inexpensive mechanic's stethoscope and try to listen my way to the problem.

I'm wondering about an external spinning accessory, like alternator/power steering pump/fan blade too.

I am wondering if it might be something internal.

Harmonic Balancer? Clutch Issue? Internal Engine Issues?

Disconnect your belts and see if it goes away.

IMHO: it doesn't go away @ any rpm.
Tere

Where is the harmonic balancer?

quote:

Originally posted by Jim and Tere:
Where is the harmonic balancer?

On the crank - typically attached in such a fashion that allows it to double as a lower pulley/belt attachment point.

Here is a wiki on the harmonic balancer

Not a Volvo - but most of this stuff applies across many engines. Cummins Diesel

Our engine does not have a harmonic balancer.
Tere

Yes you do. All the 245 series engines have them- it is part of the crankshaft pulley at the bottom of the engine. Your water pump belt is driven by it.

After looking at your engine it appears it may have a turbo? If so, a high frequency vibration could be turbo bearings in addition to the other items Bill listed. An idler bearing could also do that. You might take all the belts off and run for a short time to see if it goes away. Then add belts one at a time until you find the problem. If it is the turbo the vibration will not go away with the belts removed. After that you are dealing with internal issues to the engine.

new timing belt, new idler bearings
not a turbo '81 b23 engines no harmonic balancer

next step-remove accessory belts, start engine see what happens.

Bad spark plug wires or a bad coil can do that too. Don't skimp if you replace them.

The intriguing point of this post is that the vibration is as strong at idle as it is at higher rpm's. I've had to troubleshoot several vibrations over the years that could be described exactly like yours. However, I put those more in the class of a buzz than a vibration.

An in flight vibration/buzz on a Piper PA12 airplane. A high frequency vibration/buzz in 225 psi power oil system on a ABB gas turbine. But
the one that matches your description almost to a Tee is a buzzing sensation I had in a late 70's early 80's VW Dasher. I could feel the same buzzing in the steering wheel and the gear shift at almost any rpm.

I was much younger then and my troubleshooting skills were still developing but I remember changing the electric fuel pump, an engine temperature sensor and doing a basic tuneup. The buzzing was gone and my fuel mileage went from 17 mpg to 24 mpg.

A vibration that feels the same in amplitude and frequency all the time isn't usually associated with an accelerating or decelerating engine.

Good Luck

If the timing belt skips just one tooth, it can set up a bad vibration.

My Volvo knowledge stops at the B18, but (trying to cover all the bases, here) I would check for proper timing or (particularly) spark scatter with a timing light.

What does a vacuum gauge show? consider finding a really old mechanic who uses one and have him use it.

Does it have vacuum or centrifugal advance? Perhaps those mechanisms could be checked or fiddled with. If anything yields a change, go deeper.

bill what do you mean a really old mechanic. I had one thru it out. lenny