Do bad shuttle valves affect braking?
 

I've read a lot about replacing the shuttle valves with the kit. Quick question: would bad shuttle valves result in a spongy pedal that would be similar to a bad master cylinder? I have had the three amigos for over a year. Had pads/rotors replaced last year and brakes bled by mechanic. Still have soft pedal and don't know if I should be focusing on the Master Cylinder or Modulator.

Thanks!

When most people say bad shuttle valves, they are talking about the shuttle valve SWITCH. The switch won't cause soft pedal.

The actually valves themselves (about $800) could cause a soft pedal. Also there are o-rings you can replace on them that can leak. Any leak anywhere in the system could cause soft pedal. This is why I was recommending bleeding before and after the modulator. If that firms the pedal back up, then I'd start looking for possible leaks.

Went to the mechanic today. Had the system bled, took 1.5 hours to bleed and flush with new fluid.

They are pretty confident it is not the master cylinder. They only had 2 codes and they said both were "shuttle valve" codes.

But - I have driven this truck only a handful of times and I am wondering if that is how the pedal is supposed to be. My wife says it is as it always has been since new. I drive a 2012 Hyundai Elantra and my car is light and when I tap the brake, it is firm and responsive. Maybe the Disco just has a softer pedal.

When I brake, the pedal has a little travel, but it brakes and holds. After the bleed it felt more responsive and does the job fine.

So, the shuttle valve codes may be the valve kit or could they be the modulator itself? Mechanic says he can get a used modulator for $200.

Maybe I was just used to a sporty car brake and got the wrong impression about a "soft pedal"?

It definitely does not stop like my Mini Cooper, but it stops fine. Maybe a little mushy compared to a small car, but should not be REALLY mushy.

i don't think the pedal is too mushy now. The bleed seemed to help. i think I was used to my car where when I applied the brake, maybe it traveled an inch at most and was solid. The Disco seems to travel a bit more.