The Stovebolt Site Forums The Parking Lot Big Bolts Brake Repair...am I going in the right direction?

Hey all, sorry for another brake question but as I have been reading and searching through the threads, I haven't seen enough to confirm to myself that I am moving in the right direction here.

Truck is a 1968 C50. Brakes are of the standard issue variety with a single pot master under the hood. The master is bolted to the brake booster which is bolted to the firewall.

Last year I found the master cylinder to be failing (booster was half full of brake fluid) so I replaced it and could never get a pedal back. The truck sat over the winter and spring and I have picked back up on it this week. After days of frustration with literally no pedal, I spent about half a day with a vacuum pump bleeding the heck out of the brakes.

The good news: I have somewhat of a pedal and the truck WILL stop. This is a major advancement from earlier in the week when it was doing a whole bunch of nothing.

The bad news: The pedal is actuating the brakes really low to the floor and a couple seconds after the truck has stopped the pressure seems to bleed off and the truck will roll again if I do not put the parking brake on.

I had to throw in the towel for today but the fact that the brakes are doing something is a positive (at least in my book.

My questions:

I want to do another round of vaccuum bleeding. That's a good idea, right?

I am assuming that the shoes need adjusting to get the pedal to "pick up" earlier and get said shoes against the drums and working to slow me down. With limited time I was fishing around with a slightly wimpy slotted screw driver to try and move the adjusters but had no luck. I am hoping the right tool will do me better.

The pressure bleed freaks me out and I should note, when that happens, the pedal is on the floorboard. It isn't bleeding the pressure and causing the pedal to drop....it is all the way there already.

I have seen a couple guys that talked about installing a residual pressure valve. I am contemplating this fix if you all think that the valve in the rebuild Midland (PN 300358) master is not working.

Thanks everyone!

Brian

First, you have to get the shoes adjusted before you will have a full pedal. I run them up until I cannot turn the drum with a bar between the lug studs, then back off a tad until the drum will turn with a slight drag.
As to bleeding, I trust the old fashion way. Have someone to pump and hold the pedal while I bleed.
After these 2 procedures you should have a good pedal. Unless the shoes or drums are worn out.

Hy Brian Lohnes, did you bench bleed the master cylinder before installing it on the truck? I assume that the master cylinder is the Midland long small diameter one, is that correct?

Did you replace the vacuum booster,as well? You may have a split in the diaphragm,which will cause the booster to fill with brake fluid. I agree with Old G.M.C. Gold-you'll need to get your shoes adjusted to gain pedal. I'd do it the way he suggests. Brakes can be a ROYAL P.I.T.A.!! "Hang in there...We're all pullin' for ya!" (Quote from "Red Green")

Hey fellas!

First off, thanks all for the advice.

I will follow Old's advice on adjusting the shoes. I did bench bleed master and it is the Midland small diameter master. Wet, I have pulled apart and rebuilt the booster. All good there!

Sounds like a shoe adjustment should get you to a good pedal,and fine brakes,as long as your rear hub seals don't leak. Grease on the brake shoes will act like a "No Brake" situation. the "Steers" will grab,but that may swing your rear around,on gravel,or wet/icy pavement! I'd play it safe,and pull the hubs,(ALL),and check the wheel cylinders/shoes. More work,but better than having an accident. GOOD LUCK!!