I have serviced the master cylinder and bled the lines down on my 1 1/2 ton '49. I pumped new fluid through the whole system. I checked the vacuum line to the hydrovac unit and it seems to be solid. I bled the hydrovac unit to make sure there was new brake fluid in it. I followed the directions in the Truck Shop Manual. The only thing I haven't done is disassemble and service the hydrovac unit. The problem is that I still need to pump the brakes twice before I can stop. The first time it goes all the way to the floor, the second time it goes almost to the floor, and the third stab gives me enough brake that I can lock 'em up and it doesn't fade. The problem is that once I let go of the brake pedal for more than 5 seconds, I have to pump 'em again the same way. I do not see any evidence of fluid leaking at any of the fittings or cylinders. What did I miss?
check the archives. could be you need the "stick trick" where you leave the brakes engaged overnight. i'm in the same boat. jon
Dang ! I dunno ; It sure sound like ad adjustment problem to me ~ air in the lines will never pump up enough to lock the wheels but loose adjustment can often be overcome by repeated pumping.... There's a seperate bleeder screw for the Hydrovac , no ? . It's been too long since I worked on one , I'd hesitate to open it up before finding a repair kits , seems to me there's a leather bit that's very difficult to find . Maybe pressure bleeding will do the trick ? .
Yes, there are actually 2 bleeders on the hydrovac. I bled them both per the book. When I went back to check it a few weeks later it was still bled down and I couldn't burp any more air out of it. Checking the shop manual instructions for the hydrovac rebuild does look a bit challenging. If the leather part is hard to find, all the more reason to try to find another unit or something else that will fix the issue. I will go back and check the adjustment, especially on the back. I know about the two adjusters per wheel on the back. One is actually missing, but I was told how to "reach in" and adjust the cylinder as this was a common problem, I guess. I would like to find the parts for the rear adjusters so I could rebuild it to original. I am trying not to have to make the parts on the lathe and mill if I can avoid it.
