Clunking noise while accelerating

Date:9 July 2013 Tags:,

Kind of a clunker

Q: When I’m at a stop and then floor the accelerator pedal, a big ka-THUNK sound comes from the engine bay.  It doesn’t really happen when I accelerate softly. I’ve looked all through the engine bay to see if something is loose, but I don’t see anything. Is something wrong with my transmission?

A: The good news is there’s probably nothing wrong with your transmission. The better news is that you likely have a failed engine mount. An engine mount is usually a rubber bushing inside a metal mounting bracket used to hold the engine and transmission to the frame and isolate some of the vibration of the engine. Sometimes these mounts are fluid-filled to provide even better smoothness, but the idea is pretty much the same. When the rubber in these parts wears out, the engine can move more than it was designed to, and this usually results in a thunking noise under hard acceleration. Much like a failed shock, when one goes bad the others aren’t far behind, so replace them all. It probably makes sense to let a garage do this repair if you aren’t experienced with under-bonnet repairs – engines are heavy, and dropping one while it’s partially disconnected from the car is not great. If you have an engine hoist and some skills, exchanging motor mounts should be no sweat; plus, mounts aren’t that expensive.

By Ben Wodjdyla