I did the hydro boost conversion last year on my '79 f-150, made a massive improvement but the last few weeks I've been having an issue. When first driving the truck the brakes seem to drag, the indicator on my trailer brake controller says that the brake lights are on. After a while as the truck warms up it goes away, brake lights stay off, and the brakes don't feel like they are dragging. Any ideas of what is going on? The set-up has been trouble free for quite a while. Thanks.

Jess

 

The booster apply piston is drifting, either from incorrect pushrod adjustment or brake pedal return spring sag. These both will cause the symptoms you have when cold.

 

Is the return spring built into the hydoboost unit? I'm thinking that it isn't the pushrod length because it's been acting fine up till now. Could be wrong though. Thanks for the reply.

Jess