I had a leaky hydroboost. Bought a rebuild kit and changed 2 o-rings. It was very simple and straightforward. Reassembled everything pumped the breaks. A little spongy, no big deal as I was planning on bleading them. Start the truck to look for ps leaks. The break pettle was sucked to the floor and will not return. Turn the truck off and pump the breaks. After 15 pumps the breaks start to come back up.  I'm stumped.  Any ideas? 

Edited July 24, 20186 yr by Sean Betts
Misspelling

Sean,

 

You re-assembled something backwards, the seals got in the wrong place, or the rod coupling didn't seat.

 

I think you can get the "lever assebly" in backwards or out of place.  This will hold the spool valve in just the right spot that during start up, it thinks you have your foot on the pedal. 

 

Another possibility, is the ball at the end of the rod from the brake did not get into the coupling correctly.   So it  is too long and thinks you are pressing on it.

 

Its up to you and where you think the mistake may be.  You could take the rod out of the brake pedal.  If the truck works normally, it is the coupling or the rod.  If it is still applying the brakes, it is the position of the spool valve.

 

HTH

Hag