The Stovebolt Site Forums The Shop Area Engine Shop Brake Lock-up Problems: Don't Try This At Home

I agree w. 46Chev. It sounds exactly like the issue you'd get with the MC not retracting far enough to release the system pressure. Once that happens you'll just get a harder pedal. I was having issues getting mine set & found it was easier to set the eliptic bolt mentioned above while someone slowly depressed and released the pedal so I could see if it was binding up on the return. Also a good idea to replace the return spring if you haven't allready.

You can check the function of the HydroVac by putting your foot on the pedal and starting the motor. As soon as you get vacum you should feel the pedal go down a bit as the HydroVac kicks in. You'll also want to check all the air lines to make sure you dont have a vac leak. Odds are the HydroVac will need a rebuild, the good news is there are rebuild kits available, and if you dont feel up to tackling it there's an outfit, I think in PA, that does them. My local NAPA had all the info in thier books about who to send it to.

As for function, I have rebuilt the entire brake system on my 2-ton dump and it stops really well for something it's size, having a funtional Hydrovac makes a huge difference.
There's also a couple folks on here that have converted to HydroBoost, same concept but uses pressure from a power steering pump instead of engine vacum.