cthomasparr

Hello,

My son has a 2000 mustang convertible with over 200K miles. The car has always had a subtle knock/clunk under the floorpan that has gotten a little worse recently.

When going over slightly uneven roads, it doesn't make much noise, but I think it is still there. It is pretty consistent when he slows down quickly. I it might knock once or maybe twice on smooth pavement. Also when starting up it sometimes make the knock sound once.

He said it also happens on bumpy roads.

Has anyone had a similar problem and know a possible cause. I haven't had the car up on jack stands recently. If anyone on the forum knows of some good diagnostic information it would be greatly appreciated.

Thanks

Urambo Tauro

First thing I'd check is the exhaust components. See if any heat shields or hangers have rusted loose. Have a look at the engine & transmission mounts, too.

Daehawk

Sounds like as said a loose exhaust hanger.

cthomasparr

Thanks. the exhaust had some work done but I don't think the noise is from the exhaust. It sounds like more of a clunk than a rattle. I can't think of anything dense enough in the exhaust to make that noise

Urambo Tauro

I'm afraid there's not much that you're going to be able to diagnose over the internet. Somebody needs to get under there and start shaking things. There are only so many things under the floorpan.

Daehawk

Could be a bad U joint too.

cthomasparr

I agree that it is difficult to diagnose over the internet. I was hoping that someone might be able to point out a wear item that typically goes at that mileage that might cause the symptoms.

I replaced the transmission with my son when he got the car several years ago. I can take a look at the Ujoint again. Would that typically make a noise going over bumps?

Do you think if it is a bushing that is worn causing one of the larger suspension components to knock that this can be diagnosed with the car on ramps or on jack stands? I have not had the best luck looking at suspensions. hard to work against the springs to get anything to move.

Urambo Tauro

U-joint would be more of a constant vibration that changes with speed. But at this mileage, you should check them anyway.

If the transmission has been out, you might want to double-check those crossmember bolts. Last time I did my clutch, I torqued those bolts to spec, but they had so much crud on the threads that my torque wrench clicked too soon, and the crossmember was not held in tightly. Some new bolts took care of that.

lincolnshibuya

did you check your sway bar end links and bushing?

cthomasparr

Stupid me. Was going to take the car to a coworker who was a mechanic and I remembered the post about the trans mount bolts. Turns out the two large bolts that go into the trans had both loosened to the point I could spin them up by hand. amazing. I thing one problem solved. Thanks everyone