P3 brake bleeding problems
Posted: Tue Nov 01, 2016 8:30 pm
Many people are reporting problems getting a good front brake on the P3, the situation being worse in recent years. Since the non-availability of the original 1.125" wheel cylinder it has been usual practice to use the larger 1.25" cylinder which of course requires more fluid. Problems seem to occur with the master cylinder recouperating, i.e taking in more fluid from the resevoir if required during operation or when bleeding. The issue seems to be partly alleviated by the use of a 1" cylinder, or replacement of the 5/8" master cylinder with a 3/4" one (from certain P4/5 models).
However, the problem may be in the master cylinder itself. An excellent cross section drawing found on the website www.head2head.free-online.co.uk/Rover/mastercyl.htm which shows the path the fluid must take. Blockage of holes, distortion or absence of the wavy washer, or even the design of the currently available main seal could affect the recouperating flow so this area should be given special attention when re-assembling a refurbished cylinder.
Note that there are at least three designs of (right hand drive) P3 master cylinders and not all of the above applies to certain of them.
However, the problem may be in the master cylinder itself. An excellent cross section drawing found on the website www.head2head.free-online.co.uk/Rover/mastercyl.htm which shows the path the fluid must take. Blockage of holes, distortion or absence of the wavy washer, or even the design of the currently available main seal could affect the recouperating flow so this area should be given special attention when re-assembling a refurbished cylinder.
Note that there are at least three designs of (right hand drive) P3 master cylinders and not all of the above applies to certain of them.