Master cylinder?!

Cheeks

Registered User
I've replaced my master cylinder with one from a breaker yard because the pedal was slowly falling when applying brakes.

On to the replacement...

Fitted okay, bench bled, seemed okay.

Bleeding

Calipers
front left and back right had pressure on each press.

Front right and back left seemed to dribble when pressing and suck back just as much.

Master cylinder

Rear bleed screw (nearest to booster) pressure on every push

Front bleed screw (furthest away from booster)
Same as calipers small amount out sucking air back in

Also the fluid level goes up with the pedal down and goes down with the pedal up, don't know if it's meant to do that or not.

Need to fix ASAP anyone got any ideas?
 

fanta

Registered User
Rule I've learn from people wiser than me. ''if you think you've bled it enough. Bleed more, F you think you've bled too much, bleed more' :)

Sent from my XT1572 using Tapatalk
 

Cheeks

Registered User
Rule I've learn from people wiser than me. ''if you think you've bled it enough. Bleed more, F you think you've bled too much, bleed more' :)

Sent from my XT1572 using Tapatalk

Yeah spent a good hour or so bleeding it, one line was fine, the other one just wasn't holding pressure.
 

Stuart B

Registered User
how can it be sucking air back in? if you are doing the 2 person method you should tighten up before the pedal reaches the floor.

have you tried an eazeebleed kit <-- or whatever where you use the spare wheel to pressure bleed - some people also bleed the clutch as air gets into it affecting the brakes somehow, I think there is a VCDS tool to cycle the ABS in case that has bled dry somehow.

mine was terrible after servicing calipers but the problem was the master cylinder needed bleeding after the 4 wheels and then the 4 wheels again.
 

Cheeks

Registered User
Tried pumping gets nowhere and also 2 person closing off when down, builds up small pressure then loses it. Don't fancy spending daft money on one of those kits haha
 

ayfreetee

Registered User
These systems need to be pressure or vacuum bled, but with no more than 15 psi, as the seals can be damaged, don't forget to bleed the clutch as well as the master cylinder, fluid is supposed to be changed every two years anyway.
 

Cheeks

Registered User
That's actually a lot cheaper than I was looking at!
I ended up Replacing the seals, had to drill the circlip out, had no holes... (ATE master cylinder)

Works a lot better now, still spongy, obviously needs bleeding.

Clutch bleed, is that just from the slave? And where does it get its fluid from I noticed there's a pipe going from the side of the reservoir.
 

Stuart B

Registered User
I think bleeding the clutch is a little more than that! with a pressure bleeder I think you jam something under the pedal to stop it dropping to the floor. I don't think you should push it down - it is not on a return spring.
 

Cheeks

Registered User
Fair one, I think I'll grab one of those vacuum bleeders, no idea how it works or what to do with it, but I'm sure it will come with instructions!
 

ayfreetee

Registered User
Vacuum bleeders usually need an airline supply, gunsons eezybleed uses a spare tyre for the pressure, but do not have more than 15 psi In the tyre, you fill the bottle with brake fluid, attach the correct cap to the reservoir and pipe to the tyre, then you go around opening each nipple, until the whole system is filled with fresh fluid, but you must keep the bottle filled up, simple one man job.
 

Cheeks

Registered User
Oh that makes a lot more sense now, so it pulls on the cylinder and you fill it from the nipples?
 

ayfreetee

Registered User
No it blows on the cylinder, by pressurising the fluid in the bottle, which is pushed through a pipe into the reservoir, google it to see how it works, I've had mine for 30 years, one of the most useful tools I've owned.
 

ayfreetee

Registered User
No, those type are pressure bleeders, vacuum bleeders need an airline feed and sucks the fluid out of the nipples , whilst you top up the reservoir.
 
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