brakes on IHC 1954

treeguyinoh · Jul 13, 2008

Hello all. I have a IHC model 1954 with an Altec AM600h mounted to it. It has a vaccum over hydraulic brake system that is giving me trouble. Comes up to 30" of vac fine, but i have no resistance at the pedal, and no braking capacity. No leaks, plenty of fluid, but this is the only(and probably last) truck I have had with this system, and I don't know where to start. Any advice would be appreciated. Thanks

Ole Farmerbuck · Jul 13, 2008

Sounds like the master cylinder is bad.

Frank Boyer · Jul 13, 2008

A bad m/c or the lining way out of adjustment can cause that. Try plugging off the m/c and bleed it. If you get a pedal then work down stream. If no pedal replace the m/c. Raybestos makes clamps for the rubber brake lines that work well. They look like two 1/4" rods about 6" long beside each other and have a hinge at one end and a thuimb screw at the other end to close off the rubber lines. You clamp off the lines and see if the pedal comes up. How long since the brakes were adjusted? How long since the hydraulic system was serviced? The fluid in a brake hydraulic system needs to be changed every couple of years and adjust the brakes a couple of times a year. You may have two adjusters per wheel. Don't drive it till the brakes are fixed. Clamping off the rubber lines is easier than plugging off the m/c, so I usually do that first. If you use vise grips do not over tightendown on the rubber lines. Overtightning the rubber hoses will cause them to rupture.

juststumps · Jul 13, 2008

Ole Farmerbuck said:
Sounds like the master cylinder is bad.

that would be my guess !!!! if you have fluid in the master cylider resivour,,, and no brake pedal,, master cylinder... if you have no fluid,, then a leak.. JNHO

treeguyinoh · Jul 14, 2008

Thanks. I havent checked anything yet, this morning, brakes worked after three pumps. I have no idea why. They work well as long as you maintain a little pressure on the pedal, but after it is released, I will have to pump three times again, at which point I get brake pressure. I am going to try to test pressure on the m/c today and see what that tells me. There are no leaks as far as I can tell. Well, thanks for the help, I'll let you know how it turns out.

04superduty · Jul 14, 2008

is their an accumulator in the system that might have gone bad?

treeguyinoh · Jul 14, 2008

There is something (accumulator?) under the driver seat, kind of tuna can shaped, that is first in line from the master cylinder. It looks like it has been replaced recently. (truck was out of my possesion for a couple years) Most of the steel lines look new, I will try to find out a little from the guy who had it. Thanks again.

TimberMcPherson · Jul 16, 2008

And if that doesnt work try reinstating the fluc capacitor.

Frank Boyer · Jul 16, 2008

If you get a pedal after 3 pumps it is likely that there is air in the system. The wheel cylinder cups and m/c cups can allow air to enter the system. You probably need to pull the drums and do an inspection. You may find the wheel cylinders leaking/frozen and in need of replacement. If you are lucky a bleed and adjust could bring the brakes back to normal.