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Sierra master cylinder... Strange fenomenon
Zaphod - 19/7/07 at 11:26 AM

Hi All

I have a pretty strange problem with my master cylinder.

During bleeding of the front brakes I have a pedal travel/movement of about 4 cm, when I tighten the front nipples the pedal stops half way (2 cm travel) with a metallic sound and cant be pushed any further.
I removed the MC yesterday and "bench bleed" it with no problems. Put it back on the car and the same fenomenon occured again?!?!?

Any suggestions?

RazMan - 19/7/07 at 11:42 AM

Sounds like the back pressure is jamming the piston somehow, assuming the noise is coming from the m/c of course. Have you stripped it to inspect for wear?

adithorp - 19/7/07 at 11:43 AM

Air in the rear brakes.

Adrian

Zaphod - 19/7/07 at 12:25 PM

No, not stripped it. And yes the "Clonk" is coming from the MC.
If I loosen one of the nipples in front I can compress the MC without problems. As soon as there is preassure the half way "Clonk and dead stop" appears.

Would trapped air in the rear casuse this?

NS Dev - 19/7/07 at 12:28 PM

quote:
Originally posted by adithorp
Air in the rear brakes.

Adrian


yep, exactly right, bleed the rears and it will go away.

Zaphod - 19/7/07 at 12:56 PM

Hm, must be a airpocket in the rear...
maybe removing the rear calipers and shaking them around would do the trick?

Thx.

RazMan - 19/7/07 at 01:27 PM

Shaking them won't work - just make sure the bleed nipples are facing upwards while bleeding.

Avoneer - 19/7/07 at 04:19 PM

Yeah - don't shake.

Any air bubbles you have will break up into tiny air bubbles in the fluid.

Pat...