Brake Pedal Goes To The Floor?

xtrempickup · February 22, 2008

I have a 95 K1500 Chevy Stepside 350 truck with automatic trans. Up until today, the brake pedal was firm when pressed to stop. Well today is the first snow we've had, first ive driven it in the snow. ABS works, thats for sure. But I'm getting a pedal that when pumped will stop, but otherwise is dropping to the floor board. The fluid is an an acceptible level, it hasnt fallen. The master does show any external leaks, and the truck is a low mile truck, its a very clean body and underside 70K miles and i dont see any external leaks from lines or anything on the ground. it just totally lost pedal and only seems to make pressure or have resistance when being pumped. it has a brake booster, its not like the diesels with a hydraulic booster than runs off the PS. my question is, what should i be looking at? is the master bleeding off internally? is the booster itself possibly leaking? what is the major culprit with this type of problem other than obvious breaks in the system that sort give it away? should a master thats 13yrs old and 70K miles possibly have gone bad?

asilverblazer · February 22, 2008

When I had a master cylinder go bad, pumping had no affect. It was an internal leak, fluid would leak past the rod.

gmtech4 · February 22, 2008

does it do it sitting still or only when in an ABS event.?

xtrempickup · February 22, 2008

does it do it sitting still or only when in an ABS event.?

does it sitting still and while moving, when abs engages it has a very hard pedal and that standard abs pulse to it

xtrempickup · February 22, 2008

anybody?

badmeds · February 23, 2008

check for air in the lines, maybe bleed the brakes.

xtrempickup · February 23, 2008

check for air in the lines, maybe bleed the brakes.

dont know why air would be in them, but then again, it wasnt this was earlier til the ABS first engaged at a stop. after that it was sinking away on me. i havent touched the brakes, they have not been done recently, they are good, but they have use on them

gmtech4 · February 23, 2008

well ,if you have no leaks at all,then the m/cyl may have failed

xtrempickup · February 23, 2008

well ,if you have no leaks at all,then the m/cyl may have failed

thats what im thinking, but wanted to cover my bases before i purchased one and started taking the old one off the truck

xtrempickup · February 23, 2008

well ,if you have no leaks at all,then the m/cyl may have failed

thats what im thinking, but wanted to cover my bases before i purchased one and started taking the old one off the truck

what about the possibility of the ABS pump bleeding off pressure? i know its sort of a decoration unless its engaging. leaning toward master considering the fluid looks like mud and it still makes some pressure and the abs when it kicks in the pedal does get rock hard and it pulses like its working. level isnt falling in the reservoir.

gmtech4 · February 23, 2008

hard pedal is the result of an event,if there was a an ABS problem,there would be a code and when that happens ,there is no more ABS,just base brakes.

xtrempickup · February 23, 2008

hard pedal is the result of an event,if there was a an ABS problem,there would be a code and when that happens ,there is no more ABS,just base brakes.

so if its a ABS related problem it should throw a code and store it. funny part is that the brake light has not come on at all even tho it acts like it has no brake pedal and the ABS hasnt, usually only get an abs light when there actually is a ABS related problem

gmtech4 · February 23, 2008

both lights come on when a code is tripped

xtrempickup · February 23, 2008

both lights come on when a code is tripped

i guess the only to find out is to repace the master cylinder and see

BigScott5150 · February 23, 2008

just logged on and saw your post. i had to replace the brake booster in my 98. i was kinda having the same issues but one thing different was that i was getting a hissing noise from it.

same symptoms except for that.