ok, so the 90 12v w250 that i have sat for 4 years before i got it...i dont know if that is part of the problem or not.

but the brakes were spongy and went to the floor. also, i noticed that over the period of about a month, the brake fluid level would go down 1/4 to 1/2 inch in the larger cavity. the smaller one stayed the same. so...first i bled the brakes. didnt get any better. then i replaced the master cylinder...still no change. lastly i changed the booster...the only thing that did was turn the "anti-lock" and "brake" lights off untill the pedal reaches the floor. (before, the lights stayed on almost all the time)

if i press the brakes to the floor, let up, and press again, they feel "normal." however, i can barely stop the truck let alone atempt to pull a trailer.

whats wrong here???

 

What shape are the calipers and wheel cylinders in..

IIRC the large, or rear resivouir in teh master cylinder feeds teh front brakes..the smaller or front one feeds teh rears( someone correct me if thats wrong)..
It sounds like you have a problem in teh calipers or front lines..

 

with the age of our trucks and the rust issue that we have, you should replace all the breaks lines, what happens is break lines rub they get rusty from sitting, and they start to seap fluid out of them, if it was me i would replace all break lines, i did it to my truck and i bypasted the abs controler in the back driver side of the truck, and blead the system and my breaks are as good as new, before my breaks felt and did the exact same thing
joel

 

Are you still losing fluid?

 

Check (or replace ) the rubber lines. They are probly rotted and expanding under pressure.

My .02

 

ok, i dont know the shape of the front calipers. but i has new pads up front, and all new pads and springs in the rear. im not losing fluid anymore...but, when i check it, some always runs out the top of the master cylinder in the rear, larger, resivoir. sometimes the front, smaller, one looks low, but its not. i marked it to be sure. i was thinking that maybe the rubber lines in the front could be bad. however...wouldnt there still be pressure on the pedal? there would be resistance still.

 

If your losing fluid out of the rear resivoir it could be leaking out the back of the master cyl were the shaft from the boost comes in. Undo the bolt that hold the master to the booster and just pull it back a bit and see it theres any fluid. If so replace the master. Good luck

 

well, i dont think thats the problem. it would seem that the fluid from the front resivoir is trying to put itself in the larger one towards the booster...so that when i take the metal cap off, fluid runs out. but thats the only time that fluid leaks out. i just installed a new master cylinder and booster about a month ago. surely the new master wouldt be bad?

it just acts like there is a lot of air in the system....spongy brakes. but i have bled and bled and bled them a million times. went through a lot of extra fluid just bleeding them. at first i thought the booster was bad, so i bought a bigger one for a diff truck, but the angle on the back was too off and wouldnt work. so i bought a replacement for the dodge. im thinking about changing out the master cylinder for one that uses a plastic container and just has one resivoir. dont know if that would be better or not. or if it would solve problem or not. brakes work fine...if you pump them as you brake.