This is the fifth and final article in a series, over the course of several months, that focus upon the repair, maintenance and troubleshooting of the braking system of Series I, II and III Land Rovers. August's focus was upon squealing brakes and binding brakes. September's focus was upon brake pedal travel being excessive or spongy. October's topic was concerned with excessive brake pedal pressure and the Land Rover pulling to one side. November was about the transmission brake. This month we look at bleeding the braking system.
General advice on brake bleeding procedure for a Series Land Rover has already been given on a previous (now archived) homepage - USA homepage June 2008 - that link will open in new browser window, so you can close it and return to this page.
This month will focus upon additional problems related to the bleeding procedure and not previously dealt with.
1. Before you begin to investigate the possibility of air in the braking system, make sure the snail cam brake shoe adjusters on each wheel back plate are fully adjusted to allow minimum clearance between brakeshoe linings and the brake drum; failure to do this will cause the brake pedal to depress more than necessary and may give the impression of a soft brake pedal.
There can also be a problem with worn serrated
edges on the snail cam adjusters; this can cause the brakeshoe adjustment pin to slip on the cam adjuster. Off-road driving vibration can lead to this situation.
2. If the brake pedal feels a little spongy on first depression but solid on the second and then returns to spongy after a short interval of time, then a leaking wheel cylinder is quite likely the cause. This is best confirmed by removing the brake drum. In severe cases there may be brake fluid visible on the back plate to give you a clue. The solution is to replace the rubber seals in the wheel cylinder or fit a new brake wheel cylinder.
3. If you have recently replaced the brake shoes with new ones and the problem has just appeared, then suspect low quality brakeshoes. Non-original brakeshoe linings can be distorted or uneven - too many cheap quality and sub-standard parts are available these days for Series Land Rovers. Only buy OEM parts for the braking system - your life may depend upon it.
4. If the wheel where the air bubble is located has a single brake wheel cylinder that has two pistons in it and attempts to remove the air have failed, then it could be that there is insufficient movement in the brake pedal travel to expel the air. To overcome this the following procedure can be tried:
Remove the appropriate wheel brake drum (Land Rover supported on axle stands)
Connect a rubber tube to the bleed nipple on the back plate and lead it into a jar containing a small amount of brake fluid
Ask an assistant to slowly depress the brake pedal until both the wheel cylinders are
ALMOST fully extended
Loosen the bleed nipple and allow the brakeshoe return springs to return the pistons into their cylinders
Tighten the bleed nipple whilst the assistant continues to hold the brake pedal steady
You may need to repeat this if full satisfaction is not achieved first time.
5. Repeated or incorrectly clamping a flexible brake pipe can lead to weakening of the walls of the tube; the wall can then balloon out slightly under pressure and give the false impression of air in the system. This is most likely to occur with cheaper substitute flexible brake hoses.
6. A false impression that there is air in the system can also be created if the brakeshoe return springs are incorrectly fitted. e.g. between the brakeshoes themselves instead of between the brakeshoe and its anchor post.
A further incorrect way of fitting the return springs is to fit them infront of the brake shoes and not, as they should be, between the brake shoes and brake back plate - this mistake can cause the brake shoes to be pulled away from the backplate resulting in the adjustment
pin slipping over the adjustment cam.
If you have a 109in Series Land Rover then check that the rear brake shoes are fitted correctly; they are not identical. The distance between the hole and the adjuster pin below it(the one that the snail cam works pushes on) is about 1cm more on the leading brake shoe. It is perfectly possible to fit the leading shoe at the back, causing incorrect operation of the brake adjuster cams.
Homemade brake bleeding kit for a Series Land Rover
(To see previous homepages visit the Homepage Archives link)