Plonk sound whilst engaging brake from 20-60

S

Stonemaker

Member
 Bedale , North Yorkshire
Greetings I hope someone can help
I have a 2007 e86 3.0 si auto. 80k miles

About three weeks ago it started making a plonk noise when you activate the brake, brakes are working fine , no loss of pressure or fluid , brakes all work ok
My local garage has checked it all over and can’t find an issue, they can hear it but can’t suss out where
One minute it sounds like the top of the brake pedal but with the window down it’s under the drivers seat, my garage suggest steering column but structurally it’s all good
It’s sound mechanical like a brake pistons activating late but there are no brake stability issues or warm callipers etc

Any ideas please
 
Something daft, like a spanner left in the door storage? Yes, that had me going for about a week once. :roll:
 
Odd one - but has been known - cheap pads that aren't quite the right size that can move in the caliper carrier.
 
Just to be clear if in neutral and I press on the brakes and am I looking for a knock or not a knock then
There is no issues in selecting drive or reverse with and adverse knocks on taking up drive slowly or quickly currently
 
I have similar issue when applying brakes on slower speeds and clunck like noise is coming from right side front wheel.
 
Could it be play in a droplink, an anti roll bar bush or something like that which moves forward a bit when you brake.
 
Since OP said to suggest possibilities, I'll list things I would check, in no particular order. FCAB (front control arm bushings), Ball joints, Swaybar bushes & clamps, front struts, exhaust hangers (rubber & metal bits), motor & transmission mounts (less likely, since you say only on braking).

Most of these should have other symptoms too, so I would look at the swaybar bushes and exhaust hangers first, because these are things that took me some time to figure out. Worn or loose swaybar bushes can allow the bar to shift and make noise without affecting function much, and the same for an exhaust that shifts forward just enough to make contact but isolates fine otherwise.

Best of luck ! Please report back.
 
An interesting you tube on an older 520 had the clunk or plonk and it was down to copper greasing the pins springs and back of the pads to ensure the pad was able to release back consistently and quietly. That’s not to difficult to do to see if that’s it. YouTube The Bimmer Fixer. BMW Clunking /Clicking Noise. The actual noise is very similar and the running gear is very similar. So maybe
 
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