No brakes when going fast!

[torthen]

Hey guys, since I bought my 95 v6 4.0 3 years ago i noticed this problem. In city traffic speeds, nomal speeds, say max 30-40 mph, the brakes work ok.
But when going faster, say 50-70 mph, if I try a panic stop, the pedal gets VERY hard, as if the engine was off with no hydraulic system on, eventually the truck does brake, but not so fast as I think it should, and I have to really press that pedal in order to do so.. Suggestions?

Don´t know if it may be related, but I tried to bleed the rear right brake and no fluid came out of the nozzle after several intents..

 

[Sasquatch_Ryda]

Any fluid out of the left rear wheel cylinder? If not your RABS valve has probably gunked up and stopped the flow of fluid to the rear brakes, and not applying the brake shoes. If this is the case it would explain the longer stopping distance as speeds. If it is the RABS valve you can replace it or bypass it.

 

[martin]

If the pedal is hard to push the problem is either lack of vacuum to the booster or the booster itself.

 

[torthen]

Any fluid out of the left rear wheel cylinder? If not your RABS valve has probably gunked up and stopped the flow of fluid to the rear brakes, and not applying the brake shoes. If this is the case it would explain the longer stopping distance as speeds. If it is the RABS valve you can replace it or bypass it.

I could bleed the left (passenger´s side) rear brake with no problems, only the rear right brake didn´t run any fluid out when pressing the pedal...


Martin, the pedal is hard to push only when going somewhat fast.. is it the same?

 

[basketranger]

I believe either the abs valve has give up the ghost or you have a "gummed up" brake line or wheel cylinder. when was the last time the rear brakes were done? the wheel cylinders are cheap $10.00 a piece or so. my two cents worth change them and try to bleed system. (master cyl then rr, lr, rf, lf,) bleed system until clean fluid comes out.

 

[torthen]

I believe either the abs valve has give up the ghost or you have a "gummed up" brake line or wheel cylinder. when was the last time the rear brakes were done? the wheel cylinders are cheap $10.00 a piece or so. my two cents worth change them and try to bleed system. (master cyl then rr, lr, rf, lf,) bleed system until clean fluid comes out.

Well I bought my truck used 3 years ago, it´s a 95´... who knows. maybe they were bled 5 years ago or never...

Sorry for my ignorance, but what part is the wheel cylinder?? It´s not the bleed nipple right??

 

[pocket-rocket]

I've seen crap stop up the holes in bleeder screws. Crap as in rust and stuff from not being capped and such.

The wheel cylinder is the part that spreads the brake shoes out to contact the drum when you push on the brake pedal.

I would also check your rubber hoses for splitting/cracking/swelling too. Have someone hit the brakes really hard while you inspect them to see if any of the rubber lines are ready to give up the ghost and blow up on you. A rubber hose swelling is not letting as much pressure get to the caliper/wheel cylinder which is brake pedal effort being lost (giving longer stopping distances).