Brake Bleeding : RHD

E3_UK

Active Member
Messages
201
Reaction score
43
This is actually on my E3 and have posted in the E3 section but thought I'd raise it here to reach the wider audience :

Doing my annual brake service today, never had any issues before until today.

I take the outside pad out then restrain one piston with a clamp and pump the other one out with about four full pedal strokes bringing the piston about half way out. I then slowly push the piston fully back with a lever. I then repeat this for the other piston then replace the pad. I then repeat this process on the inside pad therefore ensuring all four pistons are free. Then usually I pump the pedal a couple of times to bring the pads into contact with the disc then repeat on the other side. The problem today is that I now have a very long travel in the pedal and can build it up to about half way with a few quick pumps. Having not disconnected any hydraulics I can't have introduced air into the system, so is this a master cylinder issue ?. It's a RHD car. With the pedal pumped up all four wheels are locked. Can a seal in the master have flipped because of the longer pedal stroke while pumping the pistons out ?. This is a procedure I perform every year but this is the first time I've had this problem. Pedal was perfect before I started doing anything.
I have read several posts on the bleeding process however having not actually introduced any air into the system I'm dubious as to why this has happened. I should also say that the reservoir level never dropped much below max whenn pumping the pistons out, I'm only pumping one piston at a time so not a huge fluid volume being displaced.
 

Cornishman

Active Member
Site Donor
Messages
486
Reaction score
88
Location
Essex, UK
I guess your system is the same as the E9 RHD, if so it has two remote servos fed by the master cylinder. The master cylinder is gravity fed from the reservoir which may also feed the clutch system. If the level in the reservoir did not drop but the pistons moved out then it sucked air Into the system. I am guessing this was via the caliper pistons or the pipe between the reservoir and master cylinder. There is a flex hose from reservoir to master cylinder, these deteriorate, usually fluid leaks down the firewall and gets the carpet wet. Look at this hose, has it closed up over age or perished? Also the master cylinder has rubber grommets that accept plastic couplers that the flex hose pushes onto, these could have perishes.
Either way I am sure that you have air in the system.
After fixing the fault then bleed the entire system, use it as a chance to change the fluid.
Use a pressure bleeder, bleed the rears first, then the front LHS followed by RHS, then the both the servo bleed points as well. Most likely then do it again. It is a such a PITA now is a good time to fit stainless hoses on each wheel, I never noticed any difference in the feel, but they look cool .
Regards
Charles
 

E3_UK

Active Member
Messages
201
Reaction score
43
I guess your system is the same as the E9 RHD, if so it has two remote servos fed by the master cylinder. The master cylinder is gravity fed from the reservoir which may also feed the clutch system. If the level in the reservoir did not drop but the pistons moved out then it sucked air Into the system. I am guessing this was via the caliper pistons or the pipe between the reservoir and master cylinder. There is a flex hose from reservoir to master cylinder, these deteriorate, usually fluid leaks down the firewall and gets the carpet wet. Look at this hose, has it closed up over age or perished? Also the master cylinder has rubber grommets that accept plastic couplers that the flex hose pushes onto, these could have perishes.
Either way I am sure that you have air in the system.
After fixing the fault then bleed the entire system, use it as a chance to change the fluid.
Use a pressure bleeder, bleed the rears first, then the front LHS followed by RHS, then the both the servo bleed points as well. Most likely then do it again. It is a such a PITA now is a good time to fit stainless hoses on each wheel, I never noticed any difference in the feel, but they look cool .
Regards
Charles
Thanks for the reply. As I pumped out each piston the reservoir level was dropping but with a single piston the displacement is very small so barely noticeable. I pumped the pedal up to compress the air then blocked it down overnight. Next day I cracked open the top bleeder on the first caliper I serviced and there was a splurge of air. I then bled the front end including master cylinders with the pressure bleeder and the pedal is fine. The air must have been in the system before I started but somehow after pumping the pistons it seems to have travelled to the master cylinder if that makes sense. Probably it was not as noticeable at the pedal when the air pocket was in the caliper but once in the master it was allowing the pedal to stroke almost to the floor before starting to move the fluid. I'm going to flush the whole system now with the pressure bleeder just to be on the safe side.
 
Top