lost my brakes today, master cylider maybe?

I was just going to the store to pick up a monster, when on the way home about a mile from my house a guy decides to pull into his driveway in front of me, i nailed my brakes, the truck almost started to slow down when the pedal just went dead to the floor. I limped it the rest of the way home and ideled into the driveway in neutral, and luckily had a long enough front yard to coast to a stop. I got out and imediatly started looking under the truck for a leak, seen nothing wet. Popped the hood and nothing leaking at the master cylider. So I pop the cap and it is full. I started it back up and pushed the pedal sever atimes, looking out the windo at the master cylinder. Nothing was squirting or any activity at all.

Did my master cylider just go out? I've had them go bad before on other cars, but they always blew out a seal or something and leaked. This one acts like theres no brake pedal. Pleas any help is greatly appreciated since this is my only driver and I have to go back to work tomarrow. Hopefully it's the master cylider and I can replace that today if thats the problem.

Thanx for any quick responses to this. Also just to mention that only the brake light came on when this happened, the abs light  never came on, so I dont think it's that fault with the abs sysemt issue, also after sitting for a bit and restarting the truck still has no brakes. And if it helps it's a 2003 cladded z71.

--Brian

Other than supposing it most likely has to do with the master cylinder, I don't know what your problem is but this isn't supposed to happen. Every vehicle sold in the US since the late '60s/early '70s has a split braking system specifically designed to prevent total failure.....only half the system can catastrophically fail at one time. I'd tow it to a good  brake shop and find out wth?

Guess you could check to see if the pedal is still connected to the ram.
I think you would see a geyser when the master cylinder seals go bad.

well figuring it was most likely the master cyl. I replaced it, spent a good hour bleeding the air out of it, then fired up the truck and bam, brakes right to the floor, this time however the master cylinder ran very low on fluid, so I looked around again and found a blown line in the front of the truck.

What I don't get it that if that blown line caused me to lose my brakes, why would I have had no brakes from that point of trying to stop, then get home, brake pedal all the way to the floor with no sign of slowing, and then still have a full master cylinder. Technically I shouldn't have had no brakes until it ran out or at least close to running out of fluid.

So this don't make much sense now, but I do know that I have to replace a line from the cylinder to the front left brake now. This just doesn't make sense though why I would lose all my brakes, then find a broken line and the reservoir still full until I replaced the master cylinder.

That's one of the problems with blown brake lines in GM trucks you can't stop them with a bad line, other vehicles you can stop them with the other 3.

Well now: that's...just...wrong...on so many levels.

motopsyco said:

well figuring it was most likely the master cyl. I replaced it, spent a good hour bleeding the air out of it, then fired up the truck and bam, brakes right to the floor, this time however the master cylinder ran very low on fluid, so I looked around again and found a blown line in the front of the truck.

What I don't get it that if that blown line caused me to lose my brakes, why would I have had no brakes from that point of trying to stop, then get home, brake pedal all the way to the floor with no sign of slowing, and then still have a full master cylinder. Technically I shouldn't have had no brakes until it ran out or at least close to running out of fluid.

So this don't make much sense now, but I do know that I have to replace a line from the cylinder to the front left brake now. This just doesn't make sense though why I would lose all my brakes, then find a broken line and the reservoir still full until I replaced the master cylinder.

Click to expand...

If no leak or loss of fluid....likely the master cylinder was bad with an internal leak in the seal between the front and rear chambers....if so, you won't see a leak and the levels in the master cylinder reservoir will remain constant....when this happens you get a soft brake and upon pressure the pedal drops slowly to the floor with no braking........you replaced the defective master cylinder and the higher pressure in the new one blew the weakest line which was ready to go anyway, and this time the level did go down in the master cylinder.

If it were me, I wouldn't stop with just the one brake line. I'd replace them all, at least the rubber parts anyway, on all 4 wheels.
If one failed the rest probably aren't in much better shape.
Unless of course the one that failed had been damaged in some way.
I just wouldn't feel safe, waiting for the next brake line to fail.

motopsyco said:

well figuring it was most likely the master cyl. I replaced it, spent a good hour bleeding the air out of it, then fired up the truck and bam, brakes right to the floor, this time however the master cylinder ran very low on fluid, so I looked around again and found a blown line in the front of the truck.

What I don't get it that if that blown line caused me to lose my brakes, why would I have had no brakes from that point of trying to stop, then get home, brake pedal all the way to the floor with no sign of slowing, and then still have a full master cylinder. Technically I shouldn't have had no brakes until it ran out or at least close to running out of fluid.

So this don't make much sense now, but I do know that I have to replace a line from the cylinder to the front left brake now. This just doesn't make sense though why I would lose all my brakes, then find a broken line and the reservoir still full until I replaced the master cylinder.

Click to expand...

You would have thought that during the bleeding process you would have seen the weak line that blew unless it just decided to blow just to make you mad. As jmuller62 said, replace all lines and hoses, otherwise you will have a nightmare when they start to go at different times and maybe a bad safety problem at the worst time. 

Good advice raiderron, replace them all.

well just as an update here. I  do believe my master cylinder did go out, and upon replacing it it blew out the front line that runs behind the bumper to the right front. I did inspect all the other lines on the truck and they all look much better than I thought they would, but that one that ran behind the front bumper actually broke into four pieces when i cut it and pulled it out. It was horrible looking and cant belive it didnt blow out sooner. I have had a fairly soft pedal for quite some time now which could have been from the master cylinder going bad. I am trying to set up an appointment to have someone come out and replace the bad section, for now I had to crimp it off and just run three brakes. I know it's not a good idea, but I only live a mile and half from work and have no other means of transportaion. Hopefully it will all be fixed this weekend.

That must be fun to drive. Pulls hard when braking?

If I just slow dont ahead of time and not hit the brakes hard, it surprisingly doesnt feel much different than before. just takes longer to come to a complete stop