Have a GMC 4000 tilt cab truck with Hydro-vac on it. Everything was froze up so found another unit off friends truck, but is a two-canister vac part. Mine is just one. The brakes work on the truck, but barely touching will put you through the windows. Can it be "over-assisted" with dual chambers? Pretty hard to drive this way. Also, almost seems like it "hangs-on" for a second or so and drags as I start to roll again. What might that mean? New Master cylinder, some lines and most wheel cylinders now. I do have to pump the brakes to get up to working position, but they stay up while I'm driving and take awhile to bleed back down, haven't figured that out yet either. No luck bleeding these, always the same results. Wonder if I to find working single chamber vac unit or have one rebuilt off parts truck I have, or just what? I'm familiar with having to send the units in, and no parts for most pop brand used around this year. Gotta try something, I wanna get driving this rig soon.
