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Terrible sound under braking... help?
Hey guys, so I've been doing work on my car and now under braking there is a THUMP thump thump thump as I slow down. Only under hard braking.
Here is what I've done. I installed a Perrin Sway bar and Perrin one piece endlinks. I drove from Eugene OR to Portland OR and back across 4 days. Call it 250 or 300 miles total. Nothing. No sounds, it was all good. On my way home, I hit a speedbump sideways and heard the slightest creak. I knew I needed to take the endlinks/sway off and regrease them. However, when I got home that Monday my Wilwood Brakes were here. I obviously immediately installed them. Everything went really well. I put the car down to 'bed' in the brakes and it started to do this thumping under braking, but the PEDAL FEEL and stability of the car is amazing. If it wasn't for the sound, you would NEVER know there was an issue. You cant feel it in the wheel or in the brake pedal. The car doesn't jerk. It doesn't stutter. I figured, maybe, that the sway bar was 'sticking' from the lack of grease problem I had earlier. (Wilwood install took a week.) I just finished redoing my whole sway/endlink system. It's greased to hell, and torqued perfectly with new bolts, even. Still getting the thump sounds under heavy breaking. If I was just light city driving, you'd never know. I'm lost. I took the wheel off, and checked the torque of everything related to the Calipers/rotors. Nothing was even a little bit loose. I'm lost. No hydraulic leaks either. any questions, ask me, I need this figured out. |
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So... since the problem happened just after you installed your brakes I'm going to go with the brakes. Seriously.... if you didn't mess with your tension rods then that just about has to be it. What forces does your swaybar see under breaking? A slight change in angle due to suspension compression from load shift? I bet there's a missing bushing or something. |
See, thats what I thought at first. Maybe the increased braking force was causing the sway bar to flex more than normal, and exaggerating any issues. Well, the sway bar is prefect right now, and I am willing to bet it isnt the issue. I might try to take the sway bar off and see if it still happens.
Other than that, I'm going to check pad wear and maybe just keep on bleeding the bleeders for a bit to see if something is happening there. There arent any bushings, except in the Endlinks, and visually, those look fine. The calipers are mounted on studs and use shims to adjust the x/y/z position of the caliper, but the disk doesnt rub or catch on the pads. The wear on the disks looks good too. I've never done brakes before, so I seriously took my time to make sure I didn't miss anything. Obviously I F'ed that up. |
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sub'd cause i like a good mystery
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Let me preface this by saying I have zero experience with this type of maintenance, so take my opinion as seriously (or not) as you like.
I agree that the problem probably originated when you installed the brakes. First question: Is the sound coming from a specific wheel or direction, or from all around/all four? If its all around, and if you aren't experiencing any loss of stopping power or vibration, my gut says its something in the braking system. Next question: Does the "thump" happen at a regular frequency, regardless of the speed you start braking at? If I had to guess based on the information so far, I wonder if you didn't quite bleed the brakes out completely and your brake system is making up for the air in the lines by pulsing to maintain an even pressure on the rotors. The lessening thump would be the result of the air in the system being compressed further and further. Again, I am fairly far from being knowledgeable, and I am guessing based on my basic knowledge and some logic. Good luck! |
the weirdest part is every time ive had an issue with brakes (air in lines, warped rotors, abs pulsating, etc) you will feel something in your pedal.
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Brakes aren't really that complicated, so it should be easy to find.
I'd also like to know if the thump frequency changes with pedal pressure, vehicle speed, etc, to see if anything causes a change. That will help narrow it down. Check the tire as well, there may be a nail or piece of debris stuck in the tread that only manifests itself under braking due to tread squirm/carcass flex, etc. If all else fails, you could bleed again (if it's something weird with the EBD system trying to compensate), or take the rotors to a brake place and have them check runout. If the rotors are defective or if there's a raised edge on a slot it would catch the pad every revolution. Also check caliper and knuckle clearances, there may be a spot of the rotor that's barely kissing the edge of something under braking. Look for witness marks. It's very unlikely it has anything to do with the swaybar, under braking there's no load on it at all, except to raise both ends simultaneously as the front end dives a bit. |
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Alright, Mystery is more or less solved.
I have the slotted rotors and after calling and talking to a Wilwood guy he said that its likely the pad is hitting the slot and causing movement as each slot comes around. Which totally makes sense. I'm just about to pull the pads and measure my disk to caliper clearances on both sides to see if I really did mess up the rotor alignment. I don't think I did, which means I simply messed up the bed in process. To fix that I have to sand down all my rotors and then re-try the bed in. The noise was only present under moderate to hard braking and always from the right front. It slowed down in frequency and got quieter as I slowed. I'll keep this updated with my clearances and such for more knowledge if someone else comes across this issue. Stay Tuned, I could always strip a bolt, lol. |
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Glad you found the (painfully obvious now) source of your problem. |
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Fixed. Just needed to be better at driving the car is all.
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