I have a 2000 ram 1500 4wd w 5.2. 115k miles. last night i was sitting at a light with my foot on the brake. the pedal suddenly sank to the floor and both the abs and brake light came on. i still have brakes, but only with pedal to the floor.

i have only had the truck for a few thousand miles, so i dont have a good history on it. this happened late at night after a 15 hour day so i havent checked the fluid level. when the truck is off the brakes pump up and hold. once i start her the pedal just sinks. i am guessing the master cylinder just went but anything else i should look for besides obvious signs of a leak in the system?

great site. i never owned a dodge before and have learned quite a bit just reading this forum the past few months.

 

The steel line running in the frame next to the gas tank probably blew.

 

^maybe, maybe not.

if the line blew out, or a wheel cylinder, then you are leaking fluid and will never get a firm pedal. also you'll have a puddle of fluid on the ground and an empty master cylinder.

on the other hand, if you have no leaks, and the master cylinder is still full of fluid, but you have a weak pedal, try pumping it up briskly about 3 or 4 good pumps. if it pumps up and then sort of slowly..... bleeds back down to the floor - then most likely your master cylinder is shot and you need to rebuild or replace it.

beware of driving it for too long in this condition. you can probably pump it up to get a pedal and get by, but if you needed an emergency stop, you'd not have time to do all that.

if you replace your master cylinder be sure and bench bleed it to save time and money on fluid and bleeding.

 

acctually, if a rear line did blow and the proportioning vavle does it's job......you could pump the pedal and get pressure with minimal fluid loss for a while, but a constant pressure on the pedal would result in a sinking pedal and noticeable fluid loss. I'm guessing it is a bad hard line myself.

 

ive done the fred flinstone style of stopping in the past and have no intentions of doing that again. thanks for the replies. my boats are my hobby and more my area of expertise. i'll have a quick go of it this weekend but most likely have it done by local shop. i just dont want to go in cold if i do it myself or have someone else do it. ill let you know what i find when i get home tonite and check the fluid level. thanks again