Master cylinder replace?

i57dwun4yb1pt8

my brake pedal started to feel a bit softer
and a little spongy over the last two months

so, this week ive changed the pads / discs all round and replaced the fluid ,
but although it stops well, it is still soft feeling and needs about half the travel to bite .

id prefer a much harder pedal .

( it doesnt drop to the floor though )

its 13 years old , audi a3 .

am i looking at an MC replace , and if so what does this cost usually ?

thanks alot

Kenny Logins

Does it slowly go to the floor if you press your foot on it? Does it firm up if you pump it? How are the flexi lines?

spiggotpaddy

But sir they're all like that.

George Dalton

These have 2 bleed screws on the master cylinder that are often overlooked. It would be worth bleeding the system again, starting with the bleed screw nearest the pedal, then the outer one on the cylinder and finally all 4 wheels.

The cylinders themselves are not troublesome at all.

i57dwun4yb1pt8

ok, i actually did this when replacing the disks / pads
I bled each brake at the caliper , ( not pushing back to the MC i blocked the flexi with a pipe clamp and pushed pistons out the local nipple
the rears i used the VAG screwback tool which was a PAIN )

missus helped be bleed the car after this . and i bled the MC at the two nips.

the calipers / flexis are all fine , i checked / cleaned up and lubed each caliper sliders etc.

pedal wont depress unless the engine is on

when engine on the pedal goes down about 45 - 50 % before a good hard bite, it used to be about 30% down before bite.
then it got spongier and softer , so thats when i reckoned new pads / disks etc needed ( disks were pretty worn in fairess)

so after all this work its actually a slightly bit worse feeling than before the work occured.

with engine on i can feel it very yery very slowly dropping if i keep good pressure on it , but it is very slow to drop- and i never waited long enough to go all way down

George Dalton

There could be some air in the ABS unit also. I would be very surprised if it was a master cylinder issue.

How long since you replaced the discs and pads? Has it been long enough for them to be fully bedded in?

i57dwun4yb1pt8

fronts have done about 80 miles rears about 40 ( did the rears a few days after the fronts )
but bled the car the day after the rears went on

city traffic , speed bumps etc .

George Dalton

That should be enough for them to be bedded in.

If I were you I would get a full system bleed done with a pressure bleeder and ideally with diagnostics to activate the ABS pump to extract any air that might be in there.

i57dwun4yb1pt8

thanks George ,
could air have gotten in BEFORE i did the work -
as i only did this work due to the brakes / pedal going soft recently ( this is why i think it may not be air ? )

George Dalton

Stranger things have happened!

Roger Mellie Man on the Telly

George Dalton wrote: »

diagnostics to activate the ABS pump to extract any air that might be in there.

Is this recommended every time you bleed brakes nowadays or only if you suspect the abs pump is 'fouled' somehow?

Thread hijack sorry.

i57dwun4yb1pt8

funny this , due to idle and general power issues , i reset the cars ECU and thottle body after some research that indicated that
after the battery was replaced , the car would basically not know how to behave ( loses its learned settings )

** i never knew this could ever be a an issue - sure learn alot about cars every time something happens to it .

i did this and the idle and power issues are now gone , shes running way better
and also for some reason the brakes are also alot better , is this my imagination or what ?