Hydro boost Rebuild Went Bad

[Jared1980]

1999 k2500 7.4 . Had leaking hydro boost from weep hole where the brake master cylinder bolts up. I took it apart and replaced the seal around the piston. On first startup the brake pedal goes all the way to the floor and will not come back up unless the engine is off. Prettty sure the brakes are being engaged fully while truck is idling. Did I put the seal in backwards causing constant pressure to the brakes or is something g not lined up with the rod from hydro boost going into the master cylinder???

 

[GoToGuy]

You assembled something incorrectly. Did you follow the OE service manual guidance? Sounds like full unregulated pressure is going to brakes.

 

[fisher]

1999 k2500 7.4 . Had leaking hydro boost from weep hole where the brake master cylinder bolts up. I took it apart and replaced the seal around the piston. On first startup the brake pedal goes all the way to the floor and will not come back up unless the engine is off. Prettty sure the brakes are being engaged fully while truck is idling. Did I put the seal in backwards causing constant pressure to the brakes or is something g not lined up with the rod from hydro boost going into the master cylinder???

I need to do the same job on my truck. What rebuild kit did you use and from where?
I need new grommets for M/C reservoir too; fluid leak around front grommet. Perhaps rebuild M/C.

 

[GoToGuy]

Grommet or "O" rings. Some have cup seals.

 

[fisher]

Grommet or "O" rings. Some have cup seals.

Good question. I'm not sure. I've only seen pictures and rubber seal described as a grommet.
I've noticed a little wettness around the rubber seal that eventually runs down and develops a slow drip.

 

[Tan1998K2500]

I made the same mistake as you when I rebuilt my hydroboost unit. The bell shaped thing has a groove in it and the pedal rod goes into that groove. I accidentally assembled it with the pedal rod on top of the bell shaped thing and it would suck the brake pedal in all the way on start up

 

[GoToGuy]

You might try this first.

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