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Old 12-05-2009, 01:54 PM   #1
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Default strange knock when transitioning from slight accel to brake

This is really starting to **** me off cuz I can't find where it's coming from. It's definitely on the passenger side and sounds like the rear. What happens is, I slightly accelerate while in traffic, clutch in, then lightly press the brake and it makes a knock sound like metal hitting metal. I cannot for the life of me figure out where it's coming from, I replaced a wheel bearing on the driver's side rear, replaced a tie rod end on the passenger front, checked to make sure the brake brackets weren't loose somehow, checked the other wheel bearings by shaking the wheel...one of the front passenger side bushings is kinda worn, but it doesn't look like it'd be enough to make a sound like that. Anyone have any ideas? Can the actual caliper be loose in the bracket?
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Old 12-05-2009, 02:08 PM   #2
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It's probably your brake caliper sliding and clamping on the rotor.
Have you tried cleaning and regreasing all the slides? Do you have the anti-rattle shims and clips?
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Old 12-05-2009, 02:24 PM   #3
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Re-torque your wheels. I had the same noise like this until I figured out that my lugs were finger tight lol.
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Old 12-05-2009, 02:43 PM   #4
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Oh yea, lugs are tight. I did the same thing once too, so that was the first thing I checked.

The slides can make a knock sound? Is it possible that the slides have widened the holes? The sound is a single knock or clunk. It sounds almost as if there was a golf ball in the trunk and when I hit the brakes it rolls and hits the trunk wall (there's not, trust me, I checked). The brakes are complete as far as I can tell. The pad squeal plates and clips are there. I should also say I haven't touched the brakes in about 20k miles. All I did back then was install new NAPA rotors.

I'll try a couple more things later today to see if I can replicate the knock sound. I haven't tried wiggling the wheel back and forth with the brake applied to see if it moves and I should probably do a high rpm accel/engine brake to make sure it's not drive train related. I'm pretty sure it's not since I should have noticed it by now if it was, but double checking is always good. To me, the speed and light brake pressure rules out suspension or bushings. They shouldn't be loaded hardly at all. Something would have to be REALLY loose.
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Old 12-05-2009, 07:28 PM   #5
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Check the rear U-joint . I had the same sound thought it was the rear breaks also, turned out to be a sized up U-joint.
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Old 12-05-2009, 07:30 PM   #6
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Quote:
Originally Posted by elderc View Post
Check the rear U-joint .
+1

I had the same problem. I replaced the driveshaft and was good to go.
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Old 12-05-2009, 09:47 PM   #7
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Are you talking about the driveshaft u-joint? If so, I just did an accel/engine brake a few times and it didn't knock. It only happens when I hit the brakes, so I can't imagine the noise could be from the driveshaft. I'll check it anyway.
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Old 12-05-2009, 09:49 PM   #8
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I'd check the brakes for anything loose, and also look over the rear suspension for slack or something obviously loose.
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Old 12-06-2009, 11:58 AM   #9
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check all bolts for wear in shanks, tighten hubs, check u-joints and CVs, pray.
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Old 12-10-2009, 11:20 PM   #10
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shake the exhaust, see if its rattling against something.
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Old 12-11-2009, 01:08 AM   #11
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i would check front ball joints by jacking the lower control arms up and shaking the wheel up and down and check for ball joint play and or, check to make sure the anti-rattle clips are on the pads i had this problem after i did a brake job left one out and it made that exact sound!
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Old 12-11-2009, 10:31 AM   #12
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I haven't changed anything on the car, so it can't be the clips unless they somehow broke off, but I'll check the ball joints. I just need time to do all this. Lack of daylight and a garage sucks.
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