three amigos again

those seals are part of the valve plungers in that big expensive assy not part of the switch pack and they can't be replaced in situ but if there was no leak leave them alone, i pointed to them just to show that oil(more correctly brake fluid) is not supposed to reach the switches, IMO they exagerated a bit on theyr site stating that oil leak to switches is the problem cos that's quite rare... but happens

I can see why the "painful" comment was given, I will elaborate as much as my fingers will allow me to type ;)

Excluding sensors, wiring faults etc... the most common issue is the shuttle valve switches. They suffer from Brake Fluid ingress and fail.

The design of the modulator has theses switches at the bottom of the unit, below (surprisingly) the shuttle valves. Over time brake fluid makes its way down into the switches and causes them to eventually fail.

The switch assembly plugs internally onto 2 pins which have been known to suffer a dry joint and it can fail when disassembled.

Here is how to test the switches: Land Rover Troubleshooting - Test Procedure And Instructions for Shuttle Valve Switches

The solution(s):

you will need a new set of shuttle valve switches (~$80.00)

you can get a kit with 2 extra seals which reseal the bottom of the shuttle valves themselves (Here is the kit with extra seals ABS shuttle valve code solution; brake fluid leaks )

Using a multimeter to test connectivity is easy, and if the connectivity is sound its just a matter of replacing the SVS assembly, refit and bleed the system.

If the connectivity of the board is broken you can fix the set up with Option B wiring bypass or there is a repair to the pins (by stripping back the plastic, re-soldering and sealing back up) most go Option B as its easier for many (no soldering skills etc).

This repair will last as long as the original if done with care.


Easy to do, time and patience should have it done within 3 hours.


Cheers

Quote:

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Originally Posted by sierrafery

those seals are part of the valve plungers in that big expensive assy not part of the switch pack and they can't be replaced in situ but if there was no leak leave them alone, i pointed to them just to show that oil is not supposed to reach the switches, IMO they exagerated a bit on their site stating that oil leak to switches is the problem cos that's quite rare... but happens

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Its EXACTLY the common cause - Take several of the units apart and you will see brake fluid on the rubber bellows sealing the switches.

Quote:

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Originally Posted by ballbag

Jeez this is a painful read.

1. Buy or borrow a Nanocom or Hawkeye.

2. Buy new switches. They will have been swimming in brake fluid for years. For the sake of, what, $80 or something? If you are going to the trouble of removing the ABS unit from the vehicle, do it once and do it properly.

3. Do "Option B". This re-routes the switch signals - instead of passing through the ABS module circuit board, they will travel along a wire. Given the fault is intermittent and increasing in frequency, it's a good bet the the circuit board is the problem.

4. Buy a couple of litres of brake fluid, read up on the bleed process and bleed the system.

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Point 2 should have included new clips and seals, as Tombie said.


You would be foolish to go to the trouble of attempting a repair without replacing such cheap parts.


Sierra, punctuation exists for a reason.

i'm not gonna contradict you, what i know is that i've done the wiring mod only 7 times for some unskilled friends, always in situ without removing the modulator, some of them made more than 50K km since, two times i found the wiring of the switches damaged(with insulation melted), only once the switch pack was fubar'd as it worked partially but with greater resistance, this was affected by fluid but we knew that from the beginning as there was a leak at the bottom of modulator... so from my own experience 1 out of 7 seemed rare... which doesnt mean the general statistic is not different...and i agree that the more new parts are included the better it is

What i forgot to mention is that i've always measured resistances across pin 8 of modulator's plug and ground to not remove the SVSs if not necessary and got greater resistance readings(some times different between two pledal pushes) than directly on the switch packs that's why my conclusion was that the most common problem is with the circuit within the shuttle valve block than with the switches, though 7 out of the hundreds or maybe thousands of cases might not be very relevant