Brakes went to the floor (hydroboost)

[mountainexplorer]

I was just thinking about how good the brakes on my diesel were. The next day, they pretty much went to the floor. It has hydroboost, and the PS pump is fine, and it's not leaking fluid anywhere from any lines or seals.

Anything different on a hydroboost system as far as why the pedal would start going to the floor? If I pump it, it seems to pump up and work up higher. Maybe it's just the master cylinder.

 

[mudjunkie 82]

sounds like air in the system.

 

[darenofears]

bleed mastercylinder and brakes

 

[mountainexplorer]

Strange though how they've worked perfect since I've had the truck, and all of a sudden they get air in the lines?

 

[K10bolts]

To test the master cylinder for an internal leak, pump up the brakes until the pedal is hard and hold. Let up a small amount while still holding pressure and watch to see if the pedal sinks.

 

[mouse]

My bet is that you had a seal go bad in the master cylinder. I've seen it dozens of times on vac-boost cars. The master cylinder here works the same way.

 

[DieselDan]

Ya, the problem is not in your hydraboost it's your mastercylinder.

I've seen hydraboost units not work at all = hard push pedal (actual failure was the power steering pump) or the hydrabooster was actually applying/dragging the brakes

Kinda surprising that you lost both halfs of your master though. Was your pedal a little low? Most of your braking force comes of the front brakes. Unless you brake pretty hard you might never realize the rears are inop. The warning light and/or lower pedal height is your only clue. I did loose a brake line right close to a master once; it sucked air back into the master and neither side (dual diagonal master cylinder) worked in about three pedal pushes

 

[mouse]

dual diagonal master cylinder

Chrysler product? I've worked on a few of those...

 

[kgblazerfive]

Mine is doing the same thing when its cold or the first time I push on the brakes, which is always when I need them the most. I also just replaced my Hydro-boost

 

[DieselDan]

Originally Posted by DieselDan
dual diagonal master cylinder

Chrysler product? I've worked on a few of those...

Nope, VW. The kicker is the brake line was worn thru. Seems every time I put the car in reverse the linkage rubbed one of the lines. After ten years of this.....