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'59 viking 60: new master; all rebuilt wheel cyl; Rebuilt hydrovac by the guys out in California that sell the kits. Can't remember who right off hand. New shoes properly adjusted, new rubber lines. Bled, bled and bled some more. No leaks. When I fired her up ,the pedal will go almost to the floor before the brakes engage. Pump it once, maybe twice and I have good pedal starting half way down. Pro truck mechanics can't get a handle on it either. Where should I be looking for my problem? ( and don't say "in the mirror" :-) I suspect it's the hydrovac.

could be the hydro..my 59 viking grain truck was a bear to bleed.then after it sat no brakes finally after moving around carefully the right rear wheel cly started leaking even after build.cly just a bit out but no pits.

Hy Mathew Blair, did you bleed according to the maintenance manual? You must bleed the hydrovac before the wheel cylinders, first bleed the upper bleed screw, then bleed the lower, out on the cylinder. After that the sequence is, left rear, right rear, left front, right front, hope that helps.

we have bled everything according to the manuals and then some. Several gallons of fluid. Me first with a pressure bleeder and then the mechanics bled it. My mechanics have it now and they do have experience on old trucks but this has got them whipped. When the Hydro was rebuilt, only the slave was rebuilt. The rebuilders did not rebuild the diaphram, but said it didn't need it. I would think that if the system is completely air free that you would have a hard pedal, but no power assist kind of like your power brakes with the car off. Is this so? Otherwise, am I not getting enough vacuum to move the diaphram properly? Or is my slave leaking? I would think that if that were the case I would have pedal but then a slow decline under pedal pressure. And where would leaking fluid go? One pump and I have good brakes. If I have air in the system, why would this be?
Thanks

MB,

The easy way to check if the Hydrovac is working is with the truck off depress the brake pedal with medium pressure. While holding the brake start the truck...if the Hydrovac is working you will feel the brake pedal fade away a little bit.

Take care,

Mike B

Hy Matthew Blair, assuming there is no air in the hydraulic system, is the master cylinder piston returning fully to its at rest position, uncovering the compensating port?

I would recheck the adjustments. Each shoe has its own adjuster. Some of those trucks had the wheel cyls. at an angle & was hard to get all the air out. I used to bleed them out the cup before I installed them. I have jacked the truck way up to level out the cyl. but we had a big air service one end lift. You might be able to do it on a steep hill, if that is the case.