I have a 1995 chev 1 ton dually truck w/ a diesel engine. I used to have a very hard pedal but one day I could push it to the floor it still stops but wants to lock up the rear and seems weak I think that the hydroboost went out but im guessing I have never delt with this type of brake system before , a new hydroboost at autozone was 301.98 if it is the hydroboost anybody know where to buy them cheaper thanks for any help chris:( :( :( :(

If your locking the rear brakes then it sounds more like a master cylender problem or air i the lines. If the hydroboost went out, it would inflict both the front and rear brakes evenly. Try bleeding the brakes and see if it gets better.

well here is the deal and see what you think about 4 months ago I replaced my front brake pads and one of the calipers were bad so I went to the store and bought one and forgot to clamp the line off so the fluid ran out when I reinstalled the calliper we bleed them by pumping the pedal 5 times and holding it while my buddy turned the zerk fitting . The pedal became harder and then I cranked the truck and we went through the same procedure again and the brakes seemed fine when i took it on the first drive it pulled hard to the right, but went away and seemed fine untill now.Also at my last oil change I checked the fluid and it needs replacing but it had some kind of abnormal slime on top what the heck is that? Thanks for your help I hope you can answer this one as well chris:) :) :)

My guess is when you manual bled the brakes, the master cylinder was extended further into the bore than it had been in a long time. If the (brake) cylinder crosses corrosion in the bore, the seal get torn; PRESTO - blown mastercylinder.

Alot of people advise against manually bleeding brakes for that reason. Although I would rather loose a mastercylinder in the garage (bleeding it) than during a panic stop during the moring commute. I, personally, dislike brake bleeders 'cause of the potential for air (moisture) contaminated brake fluid.

Except for the hydrabooster itself, the rest of the brake system is CHEAP. We spend hundreds/thousands on tires, engines, and other goodies. Brakes are a bargain in comparison (& I'm a Yankee!).;)

When bleeding your brakes make sure you start from the farthest wheel from the master cylender and work your way to the closest as the last one bled. Given the circumstances though, I'd say you've got a bad master cylender. Rebuilt's are about as cheep as a rebuild kit so I'd save yourself some time and skip the kit. Good luck!

Another question?
what do you think the slime on top of the brake fluid is from?
what would a master cyl. cost you think everything is closed in nc now?

thanks for all the replies chris:D :D :D

The whole slime thing got me thinking. It might be worth while loosening the bolts that hold the master cylender to the hydroboost and see if slime or brake fluid comes out. I just ran to the garage and mixed a little power steering fluid with dot 3 brake fluid and got a nice slime layer. If the seal was tight enough between the master cylender and the hydrabooster, its possible that a hydraboost could leak into the chamber between and force power steering fluid into the master cylender. If so, you'll probalby need to rebuild both. Last time I bought a master cylender it ran $15 - $20, I think the hydraboost was more around $90 so a rebuild kit might be better suited here.