I see many repair kits for the shuttle valve on EBAY. Which one?? How are they improved?? New O rings?? Has anyone been successful in their replacement? And lastly, what are the O rings that leak? Do they come with the kit??

 

Your question is not clear. What is it you are trying to buy? Have you gotten the ABS fault code(s) read? Do that first before buying anything. And please post a link or links to what you are seeing on eBay.

The most common problem with the Discovery II ABS module is a failed solder joint on a printed circuit inside the modulator that is not readily accessible. The famous "Option B" fix bypasses the failed printed circuit and restores full ABS, traction control and hill descent control function. If the existing shuttle valve switches pass the ohm meter resistance tests described in the Option B instructions there is no need to replace them.

The shuttle valve seals inside the modulator can also fail, leaking brake fluid onto the switches. If there is no evidence of brake fluid contamination when the shuttle valve switches are removed to complete the Option B fix there is no reason to replace the seals. One seller, Falconworks in Tucson, sells a set of shuttle valve seals and retaining clips, if you find that brake fluid is leaking.

In the case of my truck, I completed the Option B fix nearly 10 years ago. The switches passed the resistance tests and there was no evidence of brake fluid contamination, so I completed the fix without buying replacement switches or the shuttle valve seals. All has been well since then with the modulator.

 

Its the shuttle valve switch. So I had my ABS codes read "shuttle valve" fault. At least that's what the repair shop told me. So I presume, then, that the switch is what becomes faulty, due to either fluid or corrosion. Isn't the fix to replace switch or perform a bypass? Or am I not seeing something?

 

Just order a wabco shuttle valve and install it. You’ll know when you pull the old one of its bad, the wiring in mine had totally disintegrated. I didn’t do the option b, only a new shuttle valve. I’ve been ABS code free since.

https://www.roverparts.com/brakes/ca...iABEgLnSPD_BwE

 

It sounds like your understanding is correct. Your switch is malfunctioning, so you can either replace it or bypass the wiring. The bypass is known as Option B.
As mln01 says, you don't need to replace the seals unless yours are leaking. The wires on the original switch unit can corrode on their own, without there being any brake fluid leaking, so it's very possible that your current seals are fine.

 

I'm afraid I can't agree with Frank4's recommendation to replace the switches without also doing Option B. More often than not it's the failed solder connection that causes the "Shuttle Valve Switch Electrical Failure" fault, and replacing the switches does not correct the failed solder connection.

While there's nothing wrong with replacing the switches, I chose to save my money since the switches in my truck tested okay. But in the last couple years there have been more instances reported of the wiring insulation in the switch module having deteriorated badly.

If your truck is not a daily driver you could remove the switch module to test and inspect it, and then order a replacement if needed. You could also go ahead and buy the switch module from a seller that accepts returns (via Amazon Marketplace, for example) and return it if not needed. Or just spend the $50-$60 and call it a day.

But again, I don't recommend replacing the switches without doing Option B. Good luck, and let us know how it works out for you.

 

Option B corrects a deficiency in the overall design which is brought on through age, namely in the degradation of the wiring to the shuttle valve switches. Option B will prevent the occurrence (or reoccurrence) of the problem by providing a more robust path to ground for the switches to pass on to the SLABS ECU whenever the switches are actuated. It will not "resurrect" bad switches, nor will it eliminate the possibility of the switches themselves failing somewhere down the line. It will prevent new and old switches alike from losing their path to ground, which inhibits their ability pass the signal to the SLABS ECU.

 

I've repaired shuttle valve switches with absolutely ZERO insulation left on them. I used 3/32 heatshrink, performed Option B and no more issues. The biggest fix Option B does as mentioned before = fixes the internal connection on the PCB which fails.

 

So lets say that I go with Wabco repair kit. What are the O rings that prevent brake fluid from leaking in?? Are those O rings included in the kit? Or purchased separately?

 

You are tossing $$$ into the wind if you remove the shuttle valve switches and don't see a drop of brake fluid. Option B can be done for under $10.00 depending on how you do it. I prefer a 2 wire trailer harness which is 3.00 at Oreilly's Auto Parts. Then Adios Amigo's!