QUESTION
I read on the internet that bench bleeding the brake master cylinder should have been done.
I didn't, could that be part of my problem or after many brake bleeds would all the air be dispersed?
If so how would I do a post install bleed?
K.M. - Engadine, NSW
ANSWER
From experience, its not absolutely necessary to bench bleed the master cylinder on a Lotus Elan +2.
The reservoir and the master cylinder are at the highest point in the hydraulic system.
I would suggest that bench bleeding the brake master cylinder in a Lotus Europa twin cam would be beneficial.
In a Europa, the brake master cylinder is located at floor level and fluid reservoir above it.
There is a remote servo unit located in the engine bay which is at the highest point in the hydraulic system.
In this scenario the brake fluid (and any trapped air) has to move up and down gradients during the bleeding process.
With the servo at the highest point, there a potential for air to collect and sit in the servo unit.
From experience, it is straight forward to bleed the brake system in an Elan +2 when following the Lotus workshop manual here
Obtaining a firm pedal after bleeding the system is conditional on air-tight terminations plus all other system components being in serviceable condition.
As you are experiencing difficulties bleeding the brake system after recently rebuilding the master cylinder, it would be useful to commence diagnostics by checking the master cylinder operation.
The master cylinder can be checked by carefully removing the outlet pipe and then installing a 3/8" UNF bleed nipple.
Make sure to mask the pedal box and surrounding paintwork with newspaper in case of brake fluid spillage.
The master cylinder should then be bled in the usual way and finally the nipple should be closed off.
The brake pedal can then be depressed to evaluate the master cylinder operation and internal condition
When the pedal is operated, the internal rubber foot valve should immediately close off the fluid reservoir to provide a solid pedal.
If pedal pressure is maintained and the pedal continues move slowly, then either the foot valve is not sealing or cylinder bore is scored allowing fluid to escape past the main seal.
If the master cylinder pressure tests OK the bleed nipple maybe removed, the hard line reconnected and then the system should be bled per the Lotus workshop manual.
Copyright © 2015 Lotus Marques
I read on the internet that bench bleeding the brake master cylinder should have been done.
I didn't, could that be part of my problem or after many brake bleeds would all the air be dispersed?
If so how would I do a post install bleed?
K.M. - Engadine, NSW
ANSWER
From experience, its not absolutely necessary to bench bleed the master cylinder on a Lotus Elan +2.
The reservoir and the master cylinder are at the highest point in the hydraulic system.
I would suggest that bench bleeding the brake master cylinder in a Lotus Europa twin cam would be beneficial.
In a Europa, the brake master cylinder is located at floor level and fluid reservoir above it.
There is a remote servo unit located in the engine bay which is at the highest point in the hydraulic system.
In this scenario the brake fluid (and any trapped air) has to move up and down gradients during the bleeding process.
With the servo at the highest point, there a potential for air to collect and sit in the servo unit.
From experience, it is straight forward to bleed the brake system in an Elan +2 when following the Lotus workshop manual here
Obtaining a firm pedal after bleeding the system is conditional on air-tight terminations plus all other system components being in serviceable condition.
As you are experiencing difficulties bleeding the brake system after recently rebuilding the master cylinder, it would be useful to commence diagnostics by checking the master cylinder operation.
The master cylinder can be checked by carefully removing the outlet pipe and then installing a 3/8" UNF bleed nipple.
Make sure to mask the pedal box and surrounding paintwork with newspaper in case of brake fluid spillage.
The master cylinder should then be bled in the usual way and finally the nipple should be closed off.
The brake pedal can then be depressed to evaluate the master cylinder operation and internal condition
When the pedal is operated, the internal rubber foot valve should immediately close off the fluid reservoir to provide a solid pedal.
If pedal pressure is maintained and the pedal continues move slowly, then either the foot valve is not sealing or cylinder bore is scored allowing fluid to escape past the main seal.
If the master cylinder pressure tests OK the bleed nipple maybe removed, the hard line reconnected and then the system should be bled per the Lotus workshop manual.
Copyright © 2015 Lotus Marques