After a lot of work I've done (I'll detail more below), I've noticed that my brake pedal throw seems to take a while before the brakes actually engage. It isn't the traditional spongy feeling of air in the lines, but it just feels like the pedal travels further than it needs to in order to engage the brakes. I can certainly feel a slight tug when I rest my foot on the pedal, so I know it's working, but it's about halfway down before they really grip tight. It doesn't go all the way to the floor (thankfully), but it just seems like there is a lot of wasted travel from when I put my foot on the pedal and press down. When I had my main rear line fail, I plugged it off until I could fix it and I noted the front brakes were really tight, like step on the brake and they were ready to stop with no problem, but now with the lines all replaced and the rear brakes working again, the pedal isn't as tight as it was.

Up to this point, I've replaced three of four calipers and brake hoses (awaiting my fourth caliper to finish the set), master cylinder about two years ago, new pads and rotors just two weeks ago, AND an entire replacement of brake lines in the front end and the main line to the rear. The only original brake lines are the two that split off at the rear axle to each caliper and the brake hose that splits the main rear line to those other lines. There's also no ABS, even after replacing wheel hubs and distribution block (something in the wiring itself), so it's completely disabled. I've tested the brake booster and all the tests are negative for a bad one, so I don't think that could be it. I'm also wondering if it's the last caliper that might be failing because it has been sticking just enough to warm up the rim, but not smoking (the reason I'm replacing it).

I read something about adjusting the pedal itself, but not sure if that's what would fix the problem. Any ideas?

This is on a standard '01 Silverado, no 4x4.

 

Sticking caliper would'nt (in my mind) cause this issue. I can only think there is something in the abs that is the problem, yes I read you disabled it.

 

I wouldn't disagree because the ABS on these trucks are probably worse than anything else on the road, but what in the ABS would cause this?

 

air in the system. you may need an abs system bleed.

 

They wouldn't have just left air in the system after putting the new lines in, they would have bled the entire thing since they replaced nearly everything. Also, if I pump the brakes, there's no building of pressure, it all stays the same.

 

as a tech in the rust belt i replaced lines regularly; getting the symptoms you describe. If you haven't tried it and nothing else works; its something to rule out. just bc the pedal doesn't pump up doesn't 100% rule out air in the system. I have gravity, manual and pressure bled, opened p-valves on some systems to no avail...an abs bleed is something you should be doing when air has entered before or at the bpmv.

 

Well, I know they had to empty the entire system because they actually had to replace the ABS module under the cab, the bolt I used to plug it off at the time the rear line blew pulled the threads right out with it (steel on aluminum, I didn't even think about it... even though I doped it up with pipe thread tape). I'll see what happens when I replace the last caliper and bleed that side.

I just wanted to see if there was something I could try because the brakes felt awesome when I had no rear brakes

 

Hey Guys,

I have similar problem. I had spongy pedal in the past on my truck Silverado 1988 and on the dushboard red light with Brake sign was lighting till I turn of the engine. So I read several czech forums, I saw hundreds videos on youtube with this problem - solution was change the master cylinder.
So I changed master cylinder - bleed it before installation, then I bleed complete breaks, several times. I am pretty sure, there is no air in the system.

When I pump the breaks (without running engine), pedal is very strong and almost in upper position. But when I start the engine, pedal falls down almost on the floor. If I try to pump the breaks, there is no different. The pedal is still almost on the floor with running engine.
I thought it could be a problem with ABS velve, so I took it out with control unit too.

I was tried already 3 master cylinders with the same result. The breaks work, but the pedal is almost at the floor. When I stop the engine and disconnect the hose to the break booster, I can hear vacuum leakage, so I think it works as well.

Do you have please please any ideas? Specialist around for this beautiful cars are clueless and without an idea.Thanks for accepting my join and for your suggestions.

Vashek