JustRob

Hi all-

Lately been noticing a light thunking noise on rough roads, attributed it to tire noise (had six year old tires on 18" wheels but recently went to 19") but a day or so ago I [gently] went over a speed hump and heard it on the way down. For lack of a better description it sounds kind of like a backfire--quick, sharp and short, but with an ever so slight metallic sound. It's coming from the right rear. Exhaust tip on that side is 1/4 inch lower than the left side so it's looking like time for new motor mounts. I know that drooping tips and unexplained vibrations are symptoms of failing mounts, could this thunk be caused by the same? Thanks!

rob

Linnm

How are your shocks?

leknus

JustRob

Shocks seem good, but I'll have them checked too. Thanks.

Uwon

Bruce In Philly

Control arms will go bad, actually the bushings, and will clunk. However the clunking is not apparent on really rough roads.... the way to tell is when they clunk on undulations and slow speed such as turning into a parking spot over a tarmac repair. The car is heavy and the shifting load will drive a clunk. It is clunking at higher speeds on rough roads but it is pretty tough to hear or distinguish.

For engine mounts... just step back from the rear of your car and look at the exhaust tips... if one side hangs lower, they need to be replaced (not necessarily the source of clunking, but a sign to be replaced anyway)..... one side goes before the other because of the engine always twists one way. There is a third mount, forward of the transmission.... for that you will need a lift.

These cars eat control arms... so my first bet is on a bad control arm when someone hears clunking.

Peace
Bruce in Philly

JustRob

Quick interim follow up here, the source of the noise at the right rear is not motor mounts. My indy believes I have a bad strut so he's digging into that right now.

Two questions, replace both if one is bad, and will I need an alignment after they're replaced?

Thanks!

rob

Climarepair.com

replace both if one is bad - YES (if your car is over - lets say - 30k milles.

will I need an alignment after they're replaced - some (good) mechanics say is not necessary

Bruce In Philly

Unless you tech is really sure it is the struts, I recommend you go for a ride with chassis ears attached. That is the only way to know for sure... other than being able to grab onto something and duplicate the clunk. Years ago when I had the 2nd highest mileage 986/996 the dealer had seen, they didn;t know where the common wear points were.... so the foreman took me for a ride with chassis ears.... isolated it right to a particular control arm. Done.

Peace
Bruce in Philly

lmaternick

check your swaybar bushings. They will produce a sudden thump or squeak depending on how worn. Usually a DIY if you can jack.

JustRob

Final report on this, it turned out to be the top mount of the right rear strut. He said everything else looked fine, and since the left side wasn't acting up I could go ahead and leave it for now but to plan on being proactive and replacing the left side top mount at my convenience (he would have gone ahead and done both if there had been some shared labor). I just picked it up and it's quiet as a church mouse going over the same roads that made the noise noticeable.

Just curious, about how many hours labor do you all think this should have taken?

Thanks to all who replied!

rob