P 406: rear brake problem

[axaQ4]

Hi to everyone at first!

I have a serious rear brake issue. I just failed MOT becouse my rear brakes didnt work almost nothing! I tried myself with the car on stand, someone pushing the brake and i could rotate the wheel by hand easily.
The handbrake works fine.

With help from a friend we removed both calipers and found that the guide pins were completly blocked, so we fixed that and thought thats it...but we were wrong . Now one side grabs almost normaly, but the other still has really really low braking power. We bled the system of course before that. The pedal doesnt fall to the ground, the pads and discs are in good shape, also the piston moves with ease and the there is no visible evidence of any leaking AND the there are no warning lights on.

Please if anyone has any ideas...i would be glad to here them

P.S.
We suspect that maybe there are issues with the rear brake compensator, abs pump or just maybe with the pad pins which were quite corroded at sight...but forgot to clean them properly .

[jasper5]

Are the pads free in their calipers?

When you bled the brakes did the side with not much braking squirt the fluid out as fast as the other side?...If not you may have a collapsed brake hose.

Brake compensator would still give both sides braking.

Do the calipers slide freely?

Are the metal brake pipes good, ie, are they kinked at all?

[axaQ4]

Are the pads free in their calipers?

When you bled the brakes did the side with not much braking squirt the fluid out as fast as the other side?...If not you may have a collapsed brake hose.

Brake compensator would still give both sides braking.

Do the calipers slide freely?

Are the metal brake pipes good, ie, are they kinked at all?

HI!

I went to the MOT again to check the strength of th braking and it was again the same. So we actually didnt make any difference .

1)Yes when we bled the brakes it squirt more or less the same.
2)Is possible that the compensator allows such low breaking power? Doesn't it have some sort of minimum "setting"?
3)The calipers after unblocking the guide pins travel normally...i only would probably need to clean the pad pins also.
4) The pipes on first site look all in very good condition

[D9406]

I'm with Jasper on this one. My car failed MOT on rear brakes out of balance. The guide pins were severely corroded so bought new pins, I also replaced pads and discs. When I replaced the pads I noticed they were a little tight so I filed off a bit of the pad backing to allow them to slide sideways easily. Result good strong brakes, If the pads can't move you need extra braking effort to make them work and the pads can't move away from the discs on release.

[teamster1975]

That's one thing I noticed with the rear calipers; the replacement pads have "horns" on them which you need to file off to get the pad moving cleanly in the caliper without fouling.

[axaQ4]

I'm with Jasper on this one. My car failed MOT on rear brakes out of balance. The guide pins were severely corroded so bought new pins, I also replaced pads and discs. When I replaced the pads I noticed they were a little tight so I filed off a bit of the pad backing to allow them to slide sideways easily. Result good strong brakes, If the pads can't move you need extra braking effort to make them work and the pads can't move away from the discs on release.

Hi!

I will surely try to clean those pins i hope it will help or else is brake master cylinder or brake compensator changing time hehe