This is on my 1986 Exmod 110, power brakes, disk brakes in front with non-vented rotors, drums in rear.
Here is what's wrong:
1) Excessive pedal travel
2) Brake warning light comes on if I hit the brakes hard
3) Brake will "pump up" to normal level in about 3 strokes
4) Back brakes only lock up in panic braking, front brakes ineffective
5) Sharp jab on the pedal gives resistance up high briefly, then vanishes and seems like only the rear brakes are working.
Here's what I've done so far, in the order I did it:
1) Adjusted rear brakes, bled brakes
2) Replaced master cylinder, bled brakes
3) Replaced front pads, bled brakes
4) Bled brakes
None of this has made any difference. What else can I do? I was sure that the master cylinder was the culprit, since it feels like I'm just not getting sufficient line pressure to the front. But it wasn't. Could the pdwa valve cause this problem? Calipers? It doesn't pull to one side.
The pdwa valve in this truck per the military supplemental parts catalog is NRC6515.
I've found this thing plumbed into the line going to the rear brakes. It's bolted to the inside of the right frame member. Anyone know what this is? The rear brakes are working fine so I doubt this is contributing to my issue, but I don't see it showing up in the parts manual.