The Stovebolt Site Forums The Parking Lot '60-'66 Trucks Brake problem

I picked up the ’66 from the paint shop on Saturday and now the brakes are acting up. At the first light the pedal went straight to the floor. I pumped it and after a sharp pull to the left it stopped. The brakes held fine at the light. Next light same thing. If I pump twice they stop fine and hold fine, but not on the first push of the petal. A bad M/C would lose pressure while sitting at the light and I’d start creeping forward – this is not happening.

Long term I’m going to change it over to 4 wheel disc, but if I was hoping to put that off until the ’53 is finished.

Suggestions?

I have a 64 GMC, and my brakes work fine after pumping them up too. But at stoplights, they do slowly (sometimes not so slowly) lose pressure.

It's off the painters now, but when I get it back my plan was to bleed the system thinking there was air somewhere. When you say "a bad M/C" what do you mean by bad?

Your problem is a bad master cylinder. It needs to be either replaced or rebuilt. The fluid is leaking by seal in the piston. Mine holds pressure it just takes 2 pumps each time.

It's probably the residual pressure check valve in the master cylinder. Time for a rebuild.

I would give all 4 corners a visual check & a good cleaning. Check the adjustment, too. Of course, you're looking for leaks, buildup, corrosion, wear, etc.
How long before you do your modifications? It might be worth replacing the hoses, wheel cylinders, steel lines, or shoes in the meantime.

cm

What the hell is this "takes two pumps" stuff you guys are talking about?! Brakes aren't supposed to "pump up." They're supposed to work when you press the pedal the first time.
Rebuild your brake system. The vehicle you slam into might be mine!

-Brad

I agree with Brad. You shouldn't have to think about what to do when it's time to stop. You just press on the brakes and it stops. Pull all the wheels and check everything. Rebuild or replace as necessary.
Fred

I agree your residual pressure valves aren't working. You can buy separate residual pressure valves on ebay for 10-15 bucks. Pretty easy to install, and might just save someone's life.

Well, my brakes work fine.. but when they start to fade, I just have to pump them. Thanks for the info on the MC, plan is now to rebuild it... just have to wait to get it back from the painter.

if it takes 2 pumps tha brakes need adjusting, if the pedal fades you either have a leak or the master cyl is junk.

I agree that brakes should not need to be pumped to stop, that’s why it went from the shop directly to the house and there it has sat.

We decided to put the conversion ahead of everything else. The problem I ran into with it being a ¾ ton 8 lug floating rear, is no conversion kits to change the rear to disc, unless I wanted to convert to 5 lug. So I rebuilt the existing rear drums (all new parts) and I’m in the process of changing the front to disc. In for a penny in for a pound, everything is getting replaced with new – all 4 tie rod ends, sleeves, upper and lower ball joints, shocks, spindles, rotors, calibers, pads, lines, master cylinder (chrome), power booster (chrome), portioning valve (chrome), and bearings. I think I’m getting close to the $2,000 mark.

I’ll be posting a “free to a good home” for the 8 lug drums, spindles, and hubs if anyone wants them. The drums are in good shape – nice and smooth.

You are sucking in air from someplace that is why you are pumping your brakes! Not SAFE