Our 2001 Forester (175K-kms, AT) has an odd noise I can't seem to track down. When driving straight down the road at a constant speed and add a slight amount of throttle, it makes a noise that kinda sounds like something is stuck in a tire. It's a "thunk thunk thunk" noise that is quite subtle, but there.

 

There are no unusal sounds at low speed or sharp turning and the car feels normal driving. It kinda sounds like a con rod knock, but duller. It is not that, as I changed gear and the sound stayed the same, so it is not RPM dependant. It is not RPM or gear related and happens really above 60km/h and seems to go away at 100km/h, but that could just be because of wind/road noise.

 

Before I spend a whck of dough on diagnostic time at the dealer, anyone have an idea of where I could look to solve this myself?

 

Thanks!

just a thought, but how old are the tires? would start by checking them - you could possibly have a bad belt on a tire (you did mention it sounding like "something stuck in a tire")

 

also would check the strut mounts/nuts - after replacing struts on the other half's car he had one making an odd thunking noise - turned out the big nut (on the strut shaft) holding the top strut mounting plate was not quite tight enough - tightened that up and noise went away. (kind of a pain to do while on the car, but can be done!)

 

might also give a good checking to ball joints and tierod ends...

Might be a good idea to see if you can get this thing on a lift and run it on the lift. Sometimes poking around that way can keep you from pulling your hair out trying to track it down.

Yes at the very least Jack up one tire and a tire and pull each wheel. Inspect the wheel bearings, break calipers and pads. It can be a stuck caliper. Its too soon for a issue with universal joints. Also check the exhaust donuts.

 

nipper

In my search, I found a bad ball joint on the right front, and replaced it. Got rid of the noise at slow speeds (was clunking going over speed bumps, etc) but the odd moving in a straight line noise is still there. All the rest of the suspension/steering bits look good.

 

After replacing the ball joint I had it aligned, and they found everything in good order.

 

I think I'll try rotating the tires and see if that does anything, or maybe mounting the snows for a day and see if that changes it.