Strange problem with PS/Hydroboost on 1009

[emmado22]

All,

I have a strange problem with a M1009.

When running, the brakes go to the floor and the brake idiot light comes on. Steering is fine, PS pump is full of ATF, all lines are connected propperly.

When the truck is OFF and the PS system is drained, the brakes appear to work fine and feel strong.

The PS pump is pumping, the lines are connected correctly, and the Master Cylinder is full of fresh DOT 5 and the entire brake system was flushed/bled.

Any clue? The could the hydrobooster be bad? Is there any way to test it in the truck?

Thanks in advance. It just seems like one problem after another on this thing.. But the electrical system is all good to go now..

 

[EO2NMCB]

I'm sure someone will correct me, but it soulds like a bad mastercylinder. If the the hydrobooster was bad it should make the break ped harder to push, ie no power asst.

 

[Westech]

that what it sounds like to me too

 

[gimpyrobb]

Yup, I'd lean toward bad master cyl too.

 

[CCATLETT1984]

bad master for sure, happened on my buddies 1009 a few weeks ago.

 

[emmado22]

I just ordered a new one from NAPA for $40.

Thanks for the help!

 

[Hoot_223]

my suburban did that the other day new master cyl and it works fine now