Sudden Loss of Brakes

[thedukes]

Hi all

i have had a hair raising moment on way home tonight, whilst braking firmly approaching a roundabout my brakes failed, i mean totally to the floor nothing, almost like a ripped pipe in fact i only just stopped using engine and hand brake.

limped home wheels off, found a pad has lost its pad (front)... i mean to say that the meat of the pad was gone but the metal back still fixed in, there is no rubbing marks on the metal tho so it must have happened at the time.

with engine off i pumped up pedal pressure to check piston and sliders, but once started i now have no brakes, it goes to the floor, now with engine on or off, no leaks found no loss of fluid..... am at a loss help.... i have an a4 b5 quattro yr 2000 estate with abs standard (only just picked it up)

suppose quick questions are:

how can i check master cylinder is working or seals pushed past?
is there a way to check abs unit?
what do i swap out first/??

only owned it for 2 weeks and already fixing summin>>>>>>> lol cars

any suggestions please


many thanks
luke

 

[aragorn]

Have you replaced the knackered pad?

 

[thedukes]

hi sorry bit of an obvious one to miss out, i put a bit of wood in to test the system for fluid leaks, i have the new pads now installed and pushed piston back whilst bleeding through nipple on caliper.

the pedal went to the floor when they failed and then never been right since

 

[aragorn]

You may have overextended the piston and unseated or damaged the seal.

Why did you open the bleed nipple? Did you properly bleed the system now you've had the nipple open? You may have introduced a lot of air by opening the nipple.

When you install new pads, the first few pumps of the pedal will be on the floor until the caliper pushes the pistons out against the pads/disk again. Give the pedal four or 5 long slow pumps and see if it comes back. Can you look at the caliper and see if the system has obviously closed up the slack?

 

[aragorn]

PS i'm breaking this out into its own thread.