P3 brake bleeding problems

P3 brake bleeding problems

Postby p2roverman » 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.
p2roverman
 
Posts: 52
Joined: Fri Aug 28, 2009 12:52 am

Re: P3 brake bleeding problems

Postby djm16 » Mon Nov 07, 2016 1:53 am

Two common reasons for the MC to not recuperate:
1) actuating rod too long (to get higher pedal) fix: increase the free travel
2) missing or damaged wavy washer behind the MC seal fix: replace.
djm16
 
Posts: 20
Joined: Sat May 07, 2016 1:28 am

Re: P3 brake bleeding problems

Postby jp928 » Fri Jun 23, 2017 8:43 am

Its fairly common these days to refurbish wheel and master cylinders by over boring and fitting a stainless sleeve, so either saving a 1.125" cylinder (providing there is enough thickness to overbore) shouldnt be too hard, or even sleeving a 1.25" cylinder back to 1.125", which might be easier.
jp 26 Rover 9
jp928
 
Posts: 39
Joined: Fri Aug 02, 2013 6:44 am

Re: P3 brake bleeding problems

Postby jp928 » Wed Jul 12, 2017 8:55 am

In my experience of bleeding brakes, I have found 2 different methods may be used, depending on the type of system - but dont remember which is which. Basically there is the plain 'depress pedal with bleeder open, lock bleeder before raising pedal', AND 'with bleeder open, stomp HARD and fast on the pedal, hold it down while closing bleeder, then raise' - the theory being the speed of the fluid leading will drag along air bubbles that may otherwise be left inside. If difficult to get a good pedal with traditional method, try the other.
jp 26 Rover 9
jp928
 
Posts: 39
Joined: Fri Aug 02, 2013 6:44 am


Return to Early post WWII, P3 the original Rover 75 and 60

Who is online

Users browsing this forum: No registered users and 0 guests

cron