Help with braking problem

[Si_steve]

I'm not in the way of starting threads on here, But I have a problem that I have never seen/heard of before. It's probably something very simple. The car is an 08 corsa 1.4.

Right so basically when braking hard it feels as if the brakes are being let off and put back on. Now its definitly not ABS as the pedal doesnt move and there is no noise as there usualy is, and is also far too slow. It also feels more like the rears (Drum obviously). So my guess is either a spot on the drum thats become lower than the rest or a proportioning valve somewhere (doubtful). I'm going to take apart the brakes and have a look, But I would like a few opinions for PH's more experienced lot.


Thank you in advance

[deveng]

I'm gonna risk my neck and say its your ABS. I wouldn't say that the pedal moves in any car I've been in when the ABS kicks in, it just pulses. and the car is surely still in warranty, so don't take it apart yourself.

[Si_steve]

Too late not to take car apart, servicings done at home etc. Well maybe wasn't the best description in the brake pedal moving but yeah it doesnt pulse etc. But the ABS unit coud be a suspect, I'm currrently not ruling anything out.

[Lplatejohn]

Air in the system

sticking caliper

worn pads

[bigdods]

Damaged front disks can do this. Its been done to death but this is my laymans understandng (so dont shoot me). If your brakes have got hot and you then sit with the brakes on the hot pad will either transfer some pad material to the disk or the heat will change the structure of that piece of the disk.

The result is that when you brake the bit with the pad material/changed structure will be harder or more grippy than the rest of the disk. This will usually result in the brake being better/worse on that part of the disk so if you brake normally it will feel like the braking is changing , and the cr may gently rock back and forward on the brakes as it slows down.

[Si_steve]

Thank you for the suggestions guys, I'll have a look at the discs just now and i'll change the fluid at college.

[Major Fallout]

Is it an auto?

[GAjon]

Warped discs??

[Si_steve]

Manual, I'll also check that but there is no juddering when braking.

[HellDiver]

Is it the Emergency Brake Assist kicking in and out? My old Corsa C used to be very premature at activating the EBA, then deciding it wasn't needed and releasing the EBA.

[Si_steve]

HellDiver said:

Is it the Emergency Brake Assist kicking in and out? My old Corsa C used to be very premature at activating the EBA, then deciding it wasn't needed and releasing the EBA.

I never knew it had this (if it does) It's never done it before, Which is causing the concern.

[Petrolhead_Rich]

GAjon said:

Warped discs??

+1 only way you can get the pedal to move is with distortion or ABS pump.

[HellDiver]

Si_steve said:

I never knew it had this (if it does) It's never done it before, Which is causing the concern.

Was standard on my 2004 Corsa 1.2 SXI (first year ABS was standard on the Corsa). I'd be pretty confident to say it'll have it on an 08 model.