The Stovebolt Site Forums The Parking Lot Tons 'o Fun 50 1 ton brake master cylinder upgrade HELP!

Hi-
I am in the middle of up grading my brakes and I saw that wbrowne used a master cylinder from an early 70's corvette.Napa #m1974
I am having an impossible time getting the brakes to bleed. I have a stock, huck, system.
I've replaced all the hard lines. All the flexible lines are braided stainless. The front wheel cylinders are brand new.
I am literally getting nothing out of the pedal. I am wondering if my push rod is either too short or too long. It's adjustable. I made it and it is currently adjusted so there is a 1/16" before it makes contact with the piston.
I am completely stumped.
When I crack the front bleeders I get a little fluid out but it stops and the pedal never goes any further down. I assume that's the residual pressure valve doing its job, but I don't know.
It's late and maybe I'm babbling but if you can offer some insight here I'd appreciate any help or suggestions.
Thanks,
Jeremy

wow...
well i am in the middle of dis assembling everything now.
Hope something comes to light.
This is the second master cylinder I've installed, the first one wouldn't push any fluid at all. nothing was coming out of the ports at all.
This one seems to be working, but still i have no line pressure...

I'll figure this out.

Did you bench bleed the master cylinder BEFORE installing it in the truck?
Do you have residual valves in line from the master cylinder?
You may have them installed backward, that's why you aren't getting any fluid thru.
Remove the residual valves and see if the fluid will come thru the bleeders. To determine if your push rod is the wrong length. Try this:
(1)disconnect the push rod from your brake pedal and from the master cylinder.(2) Open the driver side front wheel cylinder bleeder. (3) use a screwdriver to push in the piston on the master cylinder. (4)Look to see if any fluid comes out of the bleeder as you push in the piston on the master cylinder.
You have the correct master cylinder Napa# M1974, '76 Corvette, 1.125" bore. Push rod clearance of 1/16" is OK.

I didn't bench bleed the master cylinder.
Since it had to bleeders on the cylinder its self I didn't think it was necessary.
I don't have residual pressure valves, because I think this master, since it is for a disc/drum set up already has a residual pressure valve in the front reservoir. I could be wrong...
I took the drums off and watched the wheel cylinders as someone pumped the brakes, they are moving a little so I think there may be air in the lines still.
I just rebuilt the rear wheel cylinders. they were a complete mess, I was hoping to get away with not doing them because I can't afford the new rear wheel cylinders at $100 a pop.
A month ago someone was wondering if the rears and the fronts were the same with different adjusters. I found out that they are indeed the same and that the only difference is the adjusters. They all had the same casting numbers in them. I had ordered a set of rebuild kits hoping to get lucky and did!
I'm done for the night and will hit this again tomorrow. I need my truck back on the road.
Thanks for the pushrod advice. I'll post more tomorrow.

Jeremy

You can get your wheel cylinder re-sleaved much cheaper than new ones. I had some done for less than half price of new, sorry don't have the info on the shop but they should be easy to find.
best of luck

I just discovered, after doing the brakes on my truck.
The wheel cylinders on my truck had the same bodies, same casting numbers. Only the adjusters are different.
So buy 4 of the fronts and swap the adjusters over.

My truck is a 50 1 ton with Huck brakes
Jeremy