Bleeding Twin Leading Shoe Front Brakes (SIII 109″ and 1980+ 88″)

Bleeding is always a problem on these twin leading shoe systems.  I tried bleeding conventionally with the units in place, but predictably it didn’t work, so I had to go through my usual and long winded bleeding method using an Ezibleed (a bottle pressurised by tyre pressure) and a draining jar with clear hose to the bleed nipple with as follows:

1)  chock the rear wheels and apply the hand brake;

2)   jack a front wheel up (start with the near side) and remove it, followed by the hub centre cone and the drive flange;

3)  undo the wheel bearing nuts and remove them, carefully laying them out in sequence and with correct orientation to which way each side of the inner nut was facing (inwards or outwards – mark if necessary) ;

4)  back off the shoe adjusters and remove the hub and drum as a complete unit (be careful not to drop the outer wheel bearing race as it comes off the stub axle);

5)  undo the top two bolts securing the swivel seal retaining ring and the flexi-hose bracket and remove them;

6)  undo the six bolts securing the brake backplate and stub axle to the swivel housing, using a tray or bowl to catch the oil that runs out of the two lower bolt holes.  Note that later axles have an oil catcher ring too, secured by these bolts, as seen on my modified axle (I fitted late stub axles and hubs to use the more commonly available RRC/Defender wheel bearings, which also allowed the use of these oil catchers);

7)  pull the backplate, complete with cylinders, shoes and pipework, clear of the stub axle and lay on top of the swivel housing.  Don’t deliberately separate the stub axle from the swivel, but don’t worry if the gasket was greased and opens up – it’ll seal again when bolted back later.

8)  bleed the brakes with the wheel unit held horizontally above the swivel, pipework upper-most, tilting it one way then another around an axis through both cylinders to ensure any air gap gets pressed against the aft end of each cylinder in turn, preventing air being trapped at the back of the pistonThis tipping must be done slowly,pausing at each tipped position for a few seconds, several times to ensure that air expelled from the first cylinder is into the second cylinder is removed.

9)  in true, traditional manual parlance, refitting is the reverse of removal, but remember to top up the swivel housings with EP90!

10)  repeat on the other side, and once the work is complete, test the brakes at low speed in a safe location before driving normally.  Keep a close eye on the master cylinder reservoir and Ezibleed levels throughout as you will need to start again if it drops too low.  Wash any spillages off paint or plastic immediately as brake fluid will wreck either if left more than a couple of minutes.

The rear brakes are much easier to bleed as their ports are at the very top of the bores of their cylinders (likewise pre-1980 88″ and SII 109 front brakes), needing only the vehicle to be stood level to ensure successful bleeding.

Be Sociable, Share!

Comments

  1. Hi Nick , I have redone both axles/swivel balls/bearings seals/brakes/brake lines /shocks /springs, now i have no brake f in the system . Putting all bake together , should I do each wheel as you say in this article or ?

    Thanks Michael..

  2. It always worked very well for me, Michael, where as I never gid very good results with the trick of using G-clamps or other methods to hold he pistons fully retracted (drums and shoes removed), or even with a piece of fine dishing line at the top of the pistons seals to create a small bleeding point in the top of each cylinder. It’s a more time consuming method, but it’s reliable and is the only way to get every bit of air out.

  3. Masaki Shoji says:

    I was in trouble, that can not remove air in the Front Brake cylinder of Series2A 109. It was very helpful. This way can be remove air in the cylinder.
    Thank you for providing information.

  4. Glad it worked.

    Another big source of air in the brakes is the PDWA valve on the chassis. It detects leaks, but is better replaced by the level sensing reservoir cap from a RR, Discovery or Defender, providing more reliable leak indications and allowing the removal of the valve to allow direct connection from master cylinder to the front and rear lines.

  5. Simon Swallow says:

    HI Nick, Just finished bleeding my front brakes using your method – worked very well. Next question is: I have a 2a with single line non boosted system. In the summer (dry enough to work outside!) I plan to replace with a boosted system. I have series 3 tower, but now looking for best set up. Planning a series servo to avoid cutting bodywork – and replacing the lines with new. Q1 what to use as a Master cylinder – defender or series (or other?) and Q2 – is the standard series shuttle valve/PDWA the best option ? as per your post reply above. Thanks

  6. Hi Simon,

    Sorry for the delay answering – I was away working and the system wouldn’t let me log in to reply.

    I think upgrading to a boosted system is very worthwhile. Swapping to bigger brakes or discs is an option I would advise to delay until after the servo to see whether the extra work and costs are really necessary.

    There are two SIII master cylinders for use with a servo (and you’ll need the SIII dual line pedal box assembly to mount the servo, not the single line non-assisted box). Both cylinders look very similar and attach to the same shared servo type, but one has a chunky white reservoir with round ends (for 11″ front and 10″ rear drums, single leading shoe both axles – 88″) and the other has a rectangular reservoir with sloping top for 11″ brakes front and rear with twin leading shoes at the front (109). Try to match the master to the slaves that you’re fitting as otherwise you may get pressure and braking imbalance. You will not be able to fit a Defender (or other coiler) master cylinder to the SIII servo without fettling, and it wouldn’t give the right pedal movement or response anyway. You may well still need to modify the wing top and will need the later, kinked SIII mud shield underneath the wing top to make way for the longer master cylinder assembly, but it will all fit under the standard bonnet.

    I used a brand new PWDA valve on my rebuild, but I wish I had eliminated it. It is a primitive leak detector, sensing a difference in pressure between front and rear brake systems when the pedal is pressed and a leak prevents pressurisation of a circuit. Many people believe they isolate the leaking system, but they don’t – the leak will continue until the associated side of the reservoir is empty (and a little from the other side of the reservoir from the sloshing). I still have the valve, but I also have the fluid level sensing cap from a Defender/RRC/Discovery, which fits the SIII reservoir and just needs wiring into the brake warning light circuit. The level sensing cap provides a more reliable warning as it isn’t prone to seizing, and it also doesn’t trap air and make bleeding a pig like the PDWA does. It is also a huge amount cheaper, especially from a breakers (finding a servicable, cheap, second hand PDWA is not easy as most have rusted solid).

    I hope that helps.

Speak Your Mind

*

By continuing to use the site, you agree to the use of cookies. more information

The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this.

Close