Hard to explain this feeling, but here goes:

I bought a D2a V8 with stock suspension and (probably) the factory shocks with about 75k miles on them.

Sometimes when I drive on very bumpy roads and apply brakes, it feels like the brakes give out. It feels like I slightly slide forward more than expected, and need to apply brakes even harder. Happens especially when there's a series of bumps in a row.

Is that normal? And because the wheel is temporarily in the air for a bit?

Or something coming loose or not working as it should when vibrating or whatever?

Booster issue? Vacuum hose connector coming loose (I've got a small vacuum leak coming from the plastic bit connecting to air intake, see video here from other post)? Or just old shocks? Old coils?

Already done:
- New shoes (Falken)
- Front rotors and pads replaced (Bosch)
- Brake master cylinder replaced (aftermarket; factory was leaking)
- DOT 4 fluid replaced, bled
- Upper and lower ball joints replaced

Can be ABS or EBD activity if you feel a judder in the pedal too ... what dimension tyres you have?

BTW after the brake fluid replacement did you bleed it as in the book + power bleed?

Yep mine does this; makes a buzzing noise, brake pedal vibrates & feels like it's running-on further than the brake-pedal force normally allows....

In my case it's the ABS cutting in & the ABS light on the dash comes on to verify.

I'd prefer non-ABS because of this (my BMW did the same thing in the same scenario) and braking on jolty/uneven surfaces can cause lots of false alarms - and in a real emergency the run-away sensation is alarming - rather do my own cadence braking if I want it, thanks.

Hope yours is same or something simple...

R-Two-D2 said:

In my case it's the ABS cutting in & the ABS light on the dash comes on to verify.

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If you dont confuse the TC with ABS light then you have a problem cos the ABS light is not supposed to "verify" when it kicks in , only the TC

sierrafery said:

If you dont confuse the TC with ABS light then you have a problem cos the ABS light is not supposed to "verify" when it kicks in , only the TC

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Good Point, I've not done it for a while so misremembered; I think of it as the ABS confirmation light, but now you've said so, yes it was the TC light.

sierrafery said:

Can be ABS or EBD activity if you feel a judder in the pedal too ... what dimension tyres you have?

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Tyres: 30.5" (265/60/R18)

Doesn't feel like response in the pedal, but more that my braking isn't having as much effect as expected in that moment.

sierrafery said:

BTW after the brake fluid replacement did you bleed it as in the book + power bleed?

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Mechanic did it. I hope so? I saw him do it with his colleague hitting the brake pedal while he did each wheel.

R-Two-D2 said:

Yep mine does this; makes a buzzing noise, brake pedal vibrates & feels like it's running-on further than the brake-pedal force normally allows....

In my case it's the ABS cutting in & the ABS light on the dash comes on to verify.

Click to expand...

Interesting! I don't get the buzzing noise or the pedal vibration. And I haven't seen the traction control light come either in those moments. Is there a chime too?

I will try to look at the dash next time (trying to keep eyes on the road heh), but I'm pretty sure it doesn't come on.

R-Two-D2 said:

Hope yours is same or something simple...

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Same dude, have enough problems with this car as it is.

MAF Diver said:

Mechanic did it. I hope so? I saw him do it with his colleague hitting the brake pedal while he did each wheel.

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There is a particular order to bleed them ... i asked about "power bleed" which can be carried out only with a proper diagnostic tool which has that function and if the fluid was drained then the system refilled that's compulsory so if all you saw was a man hitting the pedal and the other working at the nipples without knowing if it was done in the correct order nor power bled with diag tool it's possible that there is air in the system hence the erratic behaviour