please help brake issues

[Stevie_Fresh]

whats up guys? i cant seem to wrap my head around this. on my way to work one day, had to it the brakes hard. felt what seemed to be a pop, and my brake pedal basically went to the floor. got the truck parked, and it seemed like the brakes would work for a minute, than go away? i thought i blew the master cylinder. just noticed that the rear bank on the reservoir was very low. topped it off. is it possible that i sucked a bunch of air into the system since it was so low? pumped the brakes real good, and pedal got nice and firm. no leaks anywhere, and did this twice to be sure. someone suggested that maybe its the abs module. so i just went to unplug the abs module fuse in the under hood panel, only to find out, it has already been pulled by previous owner. and yes the abs light has been on since ive owned the truck. the pedal will stay nice and firm as long as the truck isnt running. seems like once i start it though, it obviously gets softer, but it seems too soft. can almost get it to the floor. even when running though, pumping the brakes seems to help build pressure. i had figured the abs module sounds reasonable since the light is on, and pedal sinks when truck is running, but as stated, fuse was already removed. and i figure if it was the master cylinder, pedal would be soft whether the truck was on or off right? can someone please help me figure out what the hell is going on here? lol thaks in advance.

 

[Bowesmobile]

You broke a line going to the rear brakes. If you want to fix it get a flaring tool and reuse the connectors from the old line. They're special and I couldnt find them in the aftermarket. Buy a section of metal tubing the same diameter and splice it in for as much as looks corroded. Also check your lines from the master to the ABS module. The front one gets corroded and bursts as well. Dont get that line from the dealership, go to Rock auto and purchase It. Its WAY cheaper there! The ABS fuse being pulled only deadens the electrical portion of the brakes. The hydraulic will work as normal. The pedal feels hard because the brake booster is powered by vacuum from the motor and without vacuum from the motor it will harden the pedal after the third pump. Because it runs out of vacuum. Check your rear brake lines and find that leak by having someone pump the brakes while you look underneath.

 

[Stevie_Fresh]

thanks i will check the rear lines again, although im fairly certain i didnt break one. since topping off the reservoir, i have pumped the hell out of the brakes and havent lost any fluid. or if i have its such a small amount that its not even noticeable..i havent seen anything underneath the truck either. was the first thing i checked when they went out on me, and also checked again after topping off

 

[98RedExp]

100% rear line. Look at the inside areas near the rear tires, you'll find everything soaked in brake fluid.

 

[Stevie_Fresh]

ok, so i just started the truck pumped the brakes a bunch of times, than climbed under looking all over for fluid in the rear section, hoses, near tires, and followed the lines as far as i could see. and i see no fluid, or anything dripping anywhere. is it possible (assuming brake fluid has never been changed) that being 16 years old, some may have evaporated over time? or maybe lost some when previous owner did the brakes last? and since it was low i sucked air into the system instead of fluid? brakes seem to work down at the bottom all the way near the floor, or is it possible that the master is really shot? i just think that if it was the master cylinder, brakes would go to the floor whether the truck was running or not. and as stated in original post, brakes get firm when truck is off. when its running pedal goes pretty much to the floor. im really boggled by this!!!! lol

 

[Bowesmobile]

Its time to pull the rear tires off and inspect the calipers for the rear brakes. Something let loose, and its releasing pressure causing the pedal to go to the floor. Did you check the rubber line that drops down to the the axle? Its toward the center of the truck over the rear axle. Also what about the rubber lines that connect the caliper to the hard lines on the rear axle? You are losing hydraulic pressure somewhere in the system.

 

[Bowesmobile]

I just thought about this, but if all those items clear inspection. Check the master cylinder and make sure its sending pressure to the rear feed. If not, that pop you heard was the piston or seal in the master cylinder giving out. Not common at all, but I had one vehicle that happened on. It doesnt seem likely since the fluid was low for the rear, but you never know. The rear could have been low for some time.

 

[Stevie_Fresh]

That was my in tial thought that it was the master. I only started questions whether it was something else when I seen the rear bank was low. I was also going downhill when it went out on me, so it could have all ran to the front? I also noticed that when someone pushed on the pedal, I could see fluid in the master resorvoir like shoot into the rear? Not so sure this is normal. I did inspect the hoses to rear calipers, I was looking for the rear abs sensor on the axle too, and didn't notice anything wet back there. I didn't realize there was a fluid line over the axle though?

 

[Bowesmobile]

It hangs from a crossmember on the frame and its what delivers the hydraulic pressure from the MC to the rear axle divider. Its the flexible part.

 

[Stevie_Fresh]

Heard that I'll double check it tom. Gonna try to flush and bleed the whole system too. If not I'll be replacing the master I guess..lol process of elimination