2nd Gen Non-Engine/Transmission Brake Pressure Loss

[RWMilgate]

On a 1996 3500 with 2 wheel drive anr rear wheel anti lock brakes at 50000 miles after replacing a rusted out steel brake line and bleeding the system I find the pedal is solid with the engine off but with engine running under heavy foot pressure the pedal slowly sinks to the floor. There is no loss of fluid from system and all four wheels brake normally and rear antilock works ok on road. My thinking is that the antilock valve may be leaking to the resevoir. Is their a positive check or am I overlooking something?

 

[southpaw]

you probably have the problem fixed by now but read this post very interesting ,poor rear brakes ???????, posted bu mysteryman .

 

[WestTN]

when the brakes failed the pedal went to the floor. This caused the master cylinder to go full stroke, which pushed the cups through a buildup of trash, damaging them. Now the fluid seeps around the plunger. That causes the pedal to slowly creep to the floor. soon you may smell brake fluid inside the truck. You need to rebuild or replace the master cylinder.