rear brake problem

Hi There

on a MK3 with original rear brake system ,the brake stay blocked after use, I have changed everything inside the caliper and I changed the master cylinder for a stainless steel, pressure on the disc remains constant
A little help would be welcome ...

Vincent

Hello Vincent,
Given the work you've done the only thing I can think of is that your master's pistion is adjusted to close to the port. With the piston at rest you should be able to pass compressed air freely from the reservoir to the nipple that connects with the brake line.
You can test this by locking up your brake, while the machine is on its center stand, then open the bleeder valve on the caliper. If the wheel frees up then the master is not returning far enough, if this exercise makes no difference then something is binding in the caliper.

RS

kebra said:

on a MK3 with original rear brake system ,the brake stay blocked after use, I have changed everything inside the caliper and I changed the master cylinder for a stainless steel, pressure on the disc remains constant

Click to expand...

The two Main reasons for rear brake drag on a MkIII are:

1. The master cylinder "barrel assembly" is screwed too far into the alloy housing, so the return breather port is not uncovered by the master cylinder piston cup when the brake is released, and as a result, the residual pressure within the system isn't venting to the master cylinder reservoir. This has to be set accurately (see the instructions below).







2. The original rubber brake hoses are known to collapse internally, and can often act like a "one-way" valve,-trapping fluid on the caliper side which causes drag. Any original hoses should have been replaced years ago.


Other possibilities could be:

3. Master cylinder breather port blocked, (or may not be fully drilled?)?

4. The tiny hole in the rubber part of the master cylinder "check valve" has not been punched out?

Found the problem!! the 34 years old rubber brake hose collapsed.....

Thank you L.A.B








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