Brakes: 850: this made me poo alittle urgent help needed

[marko_850_t5]

Originally Posted by RollingThunder

I may be way off track here, but bear with me

Whenever I buy a new car I give it a full workout to see how it behaves under duress - this includes hard acceleration, hard braking (full emergency stop from 50), chicane test, etc - all on deserted roads of course. My car came with 12m MoT - it was tested 5 days before I picked it up, and had no advisories. I checked it all out before doing the stress tests - no faults found. However, a few hundred miles after doing the stress test the brakes began to get spongy and I found a small weepage at the top of the brake pedal - the brake master cylinder is leaking slightly.

My theory is that normal use of the brakes only push the rod so far into the brake master cylinder. The remaining bore is not swept under normal use, and so can get corroded and maybe there is an accumilation of debris there. Doing the emergency stop pushed the rod further than normal, so the seals are dragged over this part of the bore, damaging the seals and thus causing the leak.

I'm wondering whether your emergency stop has done the same thing?

FYI a new master cylinder is around £150 from Rufe (if you have ABS and TRACS). This includes a £20 returnable exchange deposit. You may as well change the brake fluid as well - ATE Super Racing Blue (DoT4+) is about £14/litre from GSF and 1L should be enough.

i was thinking along the lines of master or slave clynder myself its booked in garage tomorrow morning see what they can make of it

the brake pedal instantly felt wrong wasnt like it braked then stopped braking half way down the travel wasnt braking from the out set

[stuartvolvo]

hi guys,
sounds to me like you have air in your breaking system, as each time you press the pedal, it will firm up. This is usually when there is air in your braking system. I would try and bleed the brakes first before you do anything else.
regards
stuart

[marko_850_t5]

Originally Posted by stuartvolvo

hi guys,
sounds to me like you have air in your breaking system, as each time you press the pedal, it will firm up. This is usually when there is air in your braking system. I would try and bleed the brakes first before you do anything else.
regards
stuart

where would you think the air came from is there a prone to weaping/leak point on the stopping system ?

[alv70d1999]

is the reservoir topped up or leaking??

[marko_850_t5]

Originally Posted by alv70d1999

is the reservoir topped up or leaking??

will go out and check

[Chris_Rogers]

I think you have two or maybe three problems:

If the master cylinder is leaking then this is clearly faulty and need replacing.

There is air in the system, possibly as a result of the leaking master cylinder.

The ABS lights being on, even if intermittently, will result in the electronic brake distribution (EBD) function (part of the ABS) being inoperative, there is no pressure reduction valve for the rear brakes it's electronic, this is why the rear brakes locked up.

[st5ve]

I was going to suggest bleeding all the brake fluid to rule out any debris or water in the system. I drained mine not that long ago, I was shocked at the amount of crud that was in the system.

Do you have stainless steel flexi brake hoses or standard? If standard check they are not perished or have bulged.

[marko_850_t5]

Originally Posted by Chris_Rogers

I think you have two or maybe three problems:

If the master cylinder is leaking then this is clearly faulty and need replacing.

There is air in the system, possibly as a result of the leaking master cylinder.

The ABS lights being on, even if intermittently, will result in the electronic brake distribution (EBD) function (part of the ABS) being inoperative, there is no pressure reduction valve for the rear brakes it's electronic, this is why the rear brakes locked up.

i have just been and checked full of fluid on the max line no leaks visable any where in the bay havent checked around the wheel arches though to see if i could see anything there

[marko_850_t5]

right picked the car up yesterday have 7 faults on the abs system pass wheel sensor rear drivers sensor one on the black circle part of the master cylnder a module in the abs cant remember the others

also system was full of air on pass front and drivers rear

blead the system now have proberbly the best brakes i have had on this car

have got it booked in at pheonix motors in haverfordwest on the 6th for a diagnosis session

so will know more then

:P

[pigpott]

i have one in the workshop at the moment with same problem we have done
servo, 1st
master, 2nd
front hoses,3rd
so all wot is left is abs pump so we bypassed it and brakes were ok
still waiting for owner to get new pump