Incorrect brake bleed or master cylinder failure?

T33_BKD

Cruiser
I just had the 312mm upgrade and the rear disks changed. Now the brake pedal goes straight to the floor, but becomes stiff when pumped a few times. however it slowly goes back down towards the floor when held. Mechanic who changed it is saying its 'definately the master cylinder' - but i recall this working perfect before going to him. Also it uses the same calipers as the standard brakes so MS shouldnt be an issue.
I have read that this could also be down to an incorrect bleeding procedure with the caliper/MS nipple.

has anyone had this issue? & which is more likely?

thanks
 

T33_BKD

Cruiser
A creeping pedal does sound like MS. Is there a bleed nipple on MS?
Dave
From what i have been reading yes.....
would this mean the garage may have buggered my MS when bleeding - and are now charging me for a new one....hmmm
 

Marshy

Settled in
If there's a bleed nipple on the master cylinder I'd make sure it's been bled there.
On cars I've done I've struggled to get a pedal after bleeding. On these cars they've had air trapped in the master cylinder.
A quick bleed at the master cured every car.
 

T33_BKD

Cruiser
If there's a bleed nipple on the master cylinder I'd make sure it's been bled there.
On cars I've done I've struggled to get a pedal after bleeding. On these cars they've had air trapped in the master cylinder.
A quick bleed at the master cured every car.
Just spoke to them, told me it had been bled from there too, but they will 'double check' tomorrow.
 

Marshy

Settled in
Usually you run the bleed procedure through vcds first then bleed the rest.
Some of the ones I've done I've had over a litre of fluid through at the calipers but still no pedal!
Then a quick bleed at the master cylinder and the pedals solid.
On older cars you used to press the pedal half way down during bleeding to stop flipping the seals over in the master cylinder, you never hear of this happening nowadays.
Good luck mate
 

T33_BKD

Cruiser
Right, so the MS was bled, but the problem is still there. They are refusing to accept liability for the "Broken" MS, claiming it was "already weak" and flushing the system has caused it to fail. Is this even possible? - especially since it was working perfect before.
I will now be out of pocket towing it to someone else to get a second opinion. Why is it so difficult to find a decent garage?!
 

T33_BKD

Cruiser
update for anyone following this: Turns out the calipers were put on upside down (bleed nipple pointing down) and rear caliper wasn't air-tight :keule:.
Master Cylinder was perfectly fine - proves its always worth getting a second opinion.
 

pluves1

Registered User
Did the first garage spot the problem or did you take it elsewhere. You should name and shame the first garage if the problem was identified elsewhere.
 

Marshy

Settled in
Glad you got this sorted mate.
I've only ever seen this once before.
Shows the original garage up a bit though.
 

T33_BKD

Cruiser
Did the first garage spot the problem or did you take it elsewhere. You should name and shame the first garage if the problem was identified elsewhere.

First garage told me to change the master cylinder for £100+ ! but they were just some backstreet cowboys - doubt anyone on here will go to them. i only went as i needed it done on the day, and thought it wasnt so hard to change - big mistake

Glad you got this sorted mate.
I've only ever seen this once before.
Shows the original garage up a bit though.

yeah, definately. complete monkeys! + thanks for your help mate
 
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