Hey guys, I’m having an issue with my hydro boost or master cylinder on my Chevy 2008 6.6 duramax. It has had a leak from the weep hole in between the master cylinder and the hydro boost unit for a while and I finally took the hydro boost out and replaced that seal and the one that’s sealing the two pieces of the hydro boost. Anyways I got it back in and all connected just like it was and bolted the master cylinder back on tight. All lines are connected just like they were. I went and pressed on the brake petal and it was building pressure just like normal but as soon as I turned the engine on, it retracts (looses pressure?) and goes to the floor. I cannot pull the petal back up and pressing on it it doesn’t move at all (locked basically) and NO power Steering aswell. This is at idle. But as soon as I turned the engine off, it starts to release the brake petal back to normal… anyone know how to fix this?

 

The power steering pump feeds pressure to both your steering gear and the hydraulic brake booster, make sure your power steering fluid is not low, and no leaks are present