Good afternoon everyone. I have been trying to get my brakes squared away for the past 6 months and am hoping someone can help get me ironed out. Right now, my main complaint is that when I first drive the truck (before it warms up a little, I have had it happen a couple times before I drove the truck a total of 400 yards, but never after that) the brake pedal feels fine at first, but when it gets close to the bottom of its stroke it starts to act like the ABS is actuating although the sound is a bit more groan in the pedal. 1 time when I have done this in my driveway I got the "service brake" message on the DIC.

When the truck is off, I have a pretty hard pedal that has less than 2 inches of travel when pumped up and it doesn't seem to drop like a bad master cylinder. When the truck is started, the pedal falls and seems like it is getting vacuum assist. The truck does seem to hover with relatively low vacuum until it warms up some, with the gauge showing virtually 0 and then goes up to the 6-8 range when warm idling. The problem did not start immediately following anything I did to the truck.

Since I started having the problem, here is what I have tried:
Checked for front pad binding and greased slides, I can now move the fronts with just grasping the pads in my hand
checked for rear shoe adjustment
bled brakes (pressure bleeder)
replaced rear drums and shoes and 1 wheel cylinder (I messed this up when putting a shoe on that was adjusted too tight)
re-bled the brakes (pressure bleeder again)
checked for material under the front wheel speed sensors (cleaned under and put sensors back)
re-adjusted rear brakes

None of the above truly seems to help, and, if I pull the ABS fuse (other than the light being on) I don't feel like there is any issue with the brakes. And likewise, after driving for a short time, even with the fuse in place, you wouldn't know there was an issue. Worst thing I can say is that the brakes aren't all that good (although they never were) and may have a tad bit of a warped front rotor that I can feel when I am really hard on the brakes.

Right now, I am at the point of replacing the front rotors and pads to something more aggressive anyway, so I was considering doing that and getting stainless front lines at the same time. Then I can take the truck to get the brakes bled at a shop, that way I can ensure the ABS unit is completely bled. So, does anyone have anything else I should check before I do that?

 

I would say replace the speed sensors. Even if they are clean they could still be sending a bad signal to the computer. If one is bad the computer would see two different wheel speeds and think one side is in a skid. That would also explain the service brake light that came on. If the condition is mild enough it might not throw a code every time

 

Low vacuum usually means a vacuum leak. Unless you have a lopey camshaft.

 

I'd get a tech 2 or something equivalent hooked up to it to see what is going on.

 

Absolutely! They are an essential tool if one wants to work on these trucks successfully. I bought one for mine.

 

The low idle vacuum was because of the cam dowel shearing on my old setup. I fixed that with my engine swap a long time ago.

I also have now replaced my front rotors and pads for 2014+ truck rotors and Wagner OEX pads. I still have a softer pedal than I'd like, but I think that is just because the brakes need to be bled using a tech 2.

 

What is different about the 2014 rotors?

 

I got police tahoe rotors specifically, but the main difference is the coating to prevent rust. The police rotor has a different vane structure for severe duty. I am hoping it helps keep them from warping during high speed stops.

 

You need to do an automated abs bleed using a scanner. It will fix your issue