Knock in the rear end.

[Polygon]

I bought this car over a month ago and I haven't been able to drive it because of a coolant issue that I couldn't fix because of an injury at work. This weekend I took care of the coolant issue. So I drove it to work today for the first time and it's making a knocking sound in the rear of car. It is rotational, if I speed up the speed of the knock increases as well. However, it doesn't always make it. On the way to work there were times it was very pronounced and then there were times you couldn't here it at all. There aren't any vibrations either. Also, when I puch the brakes the knock stops.

Yesterday I did find out that some of the wheels were missing a lug nut. So I am going to go get some lug nuts on the way home and re-torque all the lugs to spec when I get home. I just wanted some ideas of what other things I should check.

Thanks,
Clint

[2old]

Sound like your exhaust is loose...

If the exhaust is aftermarket the exhaust might be bumping up against the body due to lack of clearance. A couple things to check for:

Is it more prominant when the car is warm?
Does it happen when you first give the car gas?

I would suggest you go under and take a look... The engine will torque the exhaust upwards when you give it gas... Also check to see that your engine mounts are still good.

[Polygon]

The exhaust is stock and it does it regardless of whether the car is warm or not. It doesn't seem more prominent under acceleration. Someone else suggested I check the exhaust. I hope that is all it is. I'll get under there tonight and check it.

[3kvr4]

if you can make a vid and record the sound, then we can give you a better diagnostic.

[Polygon]

I don't have access to a video camera.

[2old]

Sorry... I missed the rotational...

If you are TT I would check the joints on the driveshaft...

[Edit: actually I would say it's too hard to say at this point... There are too many things it could be... I would first look at the exhaust because that is easy, but it could be anything from suspention to drivetrain)

[Polygon]

Someone has suggested warped rotors, which is a possiblity considering that the wheel is missing a lug nut. I guess I'll have to pull the rotor tonight and check it as well.

[3kvr4]

Originally Posted by Polygon

Someone has suggested warped rotors, which is a possiblity considering that the wheel is missing a lug nut. I guess I'll have to pull the rotor tonight and check it as well.

well you said it happend when you accelerated the engine.....Right?

[Polygon]

Originally Posted by 3kvr4

well you said it happend when you accelerated the engine.....Right?

That depends on what you mean. It only makes the sound when the car is in motion. As I speed up the knock speeds up, as I slow down the knock slows down, and if I push the brakes the knock stops.

[3kvr4]

can it be that your brake pads have no hardware on them? they might just be loose. have you used y0ur ebrake and has the rattel gone away?

[youngvr4]

it really could be anything, i had that happen to me once, come to find out, i had a fat pice of metal stuck on the side of my tire on the inside. whenever i moved it just clunked on the ground.
just gotta lift her up and check it out

[Igovert500]

Yeah, tough to say, at first I thought driveshaft u-joints or carrier bearings, but the fact that it stopped when you apply the brakes would lead me to check the brakes first. A missing lugnut could technically have caused a warped rotor, something could be interfering with the caliper. Also might not hurt to check the wheel bearings, and make sure your wheels are balanced. But check the brakes first.

[Polygon]

Yeah, sadly Checker can't get the rotors, AutoZone is trying to sell me their cheap brand, and PepBoys wants $107 per rotor.

I think I am just going to find some good blanks from a 3S vendor.

[3kvr4]

Originally Posted by Polygon

Yeah, sadly Checker can't get the rotors, AutoZone is trying to sell me their cheap brand, and PepBoys wants $107 per rotor.

I think I am just going to find some good blanks from a 3S vendor.

HOw did you come to the conclusion that it was indeed your rotors?and if it is your rotors, ive seen some for 60 each online from brembo.

[Igovert500]

if you can't find anything cheaper, this might still be going on