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#1
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Strange sensation/sound on hard braking
If I have to hit the brakes suddenly and very firmly - as if someone just cut me off, I have "thunk" that can be felt and heard. After hitting the pedal quickly and hard it sounds/feels like there is a brief delay and then they suddenly grabs very hard. Almost as if something is loose maybe even. Just doesn't feel like I am used to with ABS. Thinking its from the front for sure. Everything works as expected under light and normal braking = no clunks, sudden grabs, pulling to any side, pedal pulsing or squeaks/squeals (after I bedded in the brakes a week or so ago using Dave Zeckhausen's guide at https://www.zeckhausen.com/catalog/i...Path=6446_6443) Not sure that makes any sense...it's hard to describe. Anyone experienced this or have a clue what my issue might be?
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Current garage: 2006 X5 4.8is 2007 Lexus GS350 2011 Cadillac CTS-V Coupe |
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#2
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Does the "thunk" sound like a brake pad hitting the caliper bracket? (would be more like a sharp metallic "CLANCK")
Maybe the steel clips holding the pads in place are not placed correctly. Or maybe they have been softened or warped beyond recocnition during your Zeckhausen procedure so the pads can move a little in the brackets I had that happen to my Miata after driving around with glowing brake discs for a while, due to a Zeckhausen bedding. The steel clips had simply lost their hardening so the were not 'springy' anymore. The Zeckhausen bedding can be a little tough on the hardware. Especially when you do it in a 2.5 ton vehicle.
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__________________ 2007 E70 4.8i Sport 2004 E53 4.4i Sport - R.I.P. Last edited by Freestyler; 06-02-2018 at 10:12 AM. |
#3
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Hmm...I would say it’s not a sharp metallic sound. More of a quick, deeper knock or bang. The first few times I slammed on it and it did it, I thought I had loose cargo or something it the truck that just shifted and bumped around. Think slamming your fist down in the floor in the trunk sort of lower tone, nondescript sound.
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Current garage: 2006 X5 4.8is 2007 Lexus GS350 2011 Cadillac CTS-V Coupe Last edited by fishhouse4; 06-02-2018 at 11:19 AM. |
#4
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I would also check the caliper mounting bolts, it is possible that they are loose and or that the bushings have worn and are letting the caliper move forward under hard braking. This would cause a small lag in breaking as the caliper and pads would "drift" forward a small amount before grabbing.
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#5
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It could also be sticky pistons in your calipers. That would explain the brief delay before the brakes bite.
Did you also have this issue before you bedded your brakes?
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__________________ 2007 E70 4.8i Sport 2004 E53 4.4i Sport - R.I.P. |
#6
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Quote:
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Honestly not 100% sure on the time unfortunately. I only had it for a week or two before bedding in the brakes and I don't recall if it did it before - or if I ever had to slam on it beforehand. The squeaking all around was driving me crazy and that was my cheap fix attempt before I ordered new pads (previous owner said he had just replaced them with Bosch pads...must be crappy ones because they are dusty as hell). Luckily bedding in seams to of cured the squealing.
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Current garage: 2006 X5 4.8is 2007 Lexus GS350 2011 Cadillac CTS-V Coupe |
#7
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#8
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I pressed new bushes into the existing arms - Meyle HD - and checked the ball joint. All good.
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Wayne 2005 BMW X5 3.0d (b 02/05) 2001 BMW F650GS Dakar (b 06/01) |
#9
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Front bushing. Very easy to confirm: have someone drive the car forward on a level surface just idle engine up to about 5 mph and firmly apply the brakes.
The wheels will push back toward the back of the wheel well suddenly.
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2011 E70 • N55 (me) 2012 E70 • N63 (wife) |
#10
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If its a thunk in the trunk maybe check your rear subframe bushings?
EDIT sorry, if it seems to be from the front it's usually the thrust arm bushes as mentioned. Common wear part on E53's. You can see them from the wheelwell.
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04 X5 3.0i auto 03 X5 4.6is |
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