03 rear brake issue - as in no brakes


5 replies to this topic
  • Ga426owner

Posted June 26, 2007 - 05:54 AM

#1

Symptoms - rear brake pedal has been loseing pressure and stated to go through entire stroke - last few months as bike has sat for a while
last night I checked it and it bottoms out completely - no braking at all to rear wheel - tried pumping the pedal...did not increase pressue at all. Pads are fine - fluid is full

I assume the caliper seals are bad as the system is air tight and no leaks. If this is this is the case - do I need to replace anything else ie...piston assembly etc...

Anyone else had this issue? What else could it be?

  • grayracer513

Posted June 26, 2007 - 01:49 PM

#2

See if one of these scenarios fits:

>The pedal travel to brake contact feels normal, but there is less than normal resistance to pedal pressure. No air can be found in the system, and there are no external fluid leaks.

Likely cause: a softened brake line.

>The pedal travel to brake contact feels normal, but holding pressure on the lever causes the pedal to drop farther the longer you hold it, eventually coming to a stop. There are no external fluid leaks.

Likely cause: leaking master cylinder piston.

  • Ga426owner

Posted June 26, 2007 - 03:44 PM

#3

yep that is what I thought to but no brake fliud leaks at all.....
I am stumped.....
it is more the first scenario - it feels like air is in system but no air is. Brake petal pumping will not get any pressure to build up...period. sounds like metal to metal clanking.....maybe I should buy a new brakeline and a master cylinder rebuild kit?

What would a bad caliper seal symptom be? air in system right? no fluid leak either right?

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  • grayracer513

Posted June 26, 2007 - 04:15 PM

#4

Caliper seals are not normally a source of air getting in, because the caliper piston moves very little. It's probably the master.

The way the rear brake is routed, there's a great big place for a bubble to live right where the line attaches to the M/C. Be sure the master is full, crack the fitting loose, and push the caliper piston back a little. Then, push the pedal down and hold it, tighten the fitting, and release the pedal.

Remember that you'll have to pump the caliper back out.

  • 642MX

Posted June 26, 2007 - 04:21 PM

#5

I've never had any luck manually bleeding brakes on a MX bike. A vacuum bleeder makes bleeding brakes easy.

  • Ga426owner

Posted June 26, 2007 - 04:43 PM

#6

Caliper seals are not normally a source of air getting in, because the caliper piston moves very little. It's probably the master.

The way the rear brake is routed, there's a great big place for a bubble to live right where the line attaches to the M/C. Be sure the master is full, crack the fitting loose, and push the caliper piston back a little. Then, push the pedal down and hold it, tighten the fitting, and release the pedal.

Remember that you'll have to pump the caliper back out.


crack the fitting loose at the brakeline & M/C, by pushing the piston, this should force air if trapped there out......hmm thanks Grey I will try this....

bleeding the brakes is the easy part for me....:thumbsup:





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