Brake trouble

[BluTrukker]

I have a 68 non power drums all around, and I seem to have lost brakes. The PO rebuilt the entire brake system except the master cylinder. Brakes have worked great up to now. The other day I went for a short trip and steadily lost braking as the trip progressed. I stopped at a gas station and checked the MC and it was nearly empty in the rear half. I have not torn anything apart as I don't have time for the next few weeks, and I don't see any obviuos signs of leakage. My initial thought is rear cylinders, but there is no fluid leaking out of the drums. Could the master cylinder be crapping out? Anyone have this issue and can point me in the right direction so I don't spend too much time chasing it down? I still have some brakes when I push it too the floor, but not much.

[mclairmo]

Check for fluid under the Master Cylinder or inside where the Master bolts to the firewall. If no fluid is leaking from the Master, then check all wheel cylinders.

[Boog]

You probably need to crawl under it and look the hard lines over for leakage at a joint or rust through places along the frame rail. Also check the rubber lines.

[68gmsee]

Good advice on previous posts... You cannot have fluid loss without a leak somewhere. Even if it's not obvious to you, it is leaking somewhere. Those rubber lines can crack and it is possible you may have a very small leak in one of them that may not be visible. The brake cylinders may be seeping a slight amount and causing the problem also.

Brakes are nothing you want to fudge on, so if you haven't redone them in a while or aren't sure of their condition, I'd invest $100-$150 and get all new cylnders, brake hoses (if original) master cylinder and brake shoes. It's a small price to pay for security.

[BluTrukker]

The previous owner ran all new lines,cylinders, and shoes. Up to this point they have worked perfect. Then all of a sudden no brakes. I crawled under the truck and looked it over and saw no signs of leaks whatsoever. I haven't pulled the wheels yet, (due to lack of time) but I just can't see losing that much fluid without having it run out of the drums or down the backing plate. I guess if it was a slow leak over time it could just goober up inside the drums and not show outside. The MC is the only original part in the brake system, so I'm a little leary about that. Oh well, winters coming soon and I need to tear into some other things too. Thanks for the help

[68gmsee]

If you know and have checked it out for yourself that the brakes cylinders, hoses and shoes are new or in good condition, then the master cylinder (they're cheap) should be replaced.

The reason I mention to be careful is because brake failure happened to me... I was driving down the road on my 69 going the usual 60-65 and was slowing down to turn. The brakes went all the way down and and it was panic pumping time! Luckily, I was on a country road and was able to pump up enough pressure to stop the truck. Got home using the parking brake mostly... Slow progress.

[BluTrukker]

Yeah, I checked everything out when I bought it 2 yrs ago, and I wouldn't think the cylinders would go bad in that amount of time. I just need to find some time to tear into it and root out the problem. If I need a new MC, can I put a power brake booster on and use all of my existing lines and cylinders?

[jjsledd]

Originally Posted by BluTrukker

The previous owner ran all new lines,cylinders, and shoes. Up to this point they have worked perfect. Then all of a sudden no brakes. I crawled under the truck and looked it over and saw no signs of leaks whatsoever. I haven't pulled the wheels yet, (due to lack of time) but I just can't see losing that much fluid without having it run out of the drums or down the backing plate. I guess if it was a slow leak over time it could just goober up inside the drums and not show outside. The MC is the only original part in the brake system, so I'm a little leary about that. Oh well, winters coming soon and I need to tear into some other things too. Thanks for the help

FWIW, that is exactly what happened with my chevelle. No signs of leaks anywhere so I thought it must be the MC, since it's the original, or somewhere in the brake line. Then I pull the rear drums off and the wheel cylinders (replaced 3 years prior to this) had leaked out with the fluid staying in the drums and caking to all the grime and dirt.

[mr48chev]

I think you may have problems with the length of the lines between the master cylinder and the equalizer valve if you swap to power but that shouldn't be that hard to make right.
Lots of good advise in the previous posts an no bad advise for once.
I'd first be looking below the mastercylinder and behind it inside the cab. You can probably move the boot around the pushrod enough to see if there are signs of fluid there.
Then check each wheel cylinder and check each hard and rubber line and fitting.

On these trucks sitting still for long periods of time is probably the hardest thing on brake cylinders. I've seen way too many of my own an customers when I did brakes on a daily basis start leaking because the rig was parked for long periods of time.

[68gmsee]

Since you're short on time, I'd just replace the MC for now and then come back with the power brakes booster later.

I put a booster in my 68 GMC using the same master cylinder (they're the same) and I didn't have to lengthen the brake lines. As a matter of fact, I didn't even disconnect the brake lines. Just moved everything forward. Not sure if you can do that with evey year.

[mclairmo]

Originally Posted by jjsledd

FWIW, that is exactly what happened with my chevelle. No signs of leaks anywhere so I thought it must be the MC, since it's the original, or somewhere in the brake line. Then I pull the rear drums off and the wheel cylinders (replaced 3 years prior to this) had leaked out with the fluid staying in the drums and caking to all the grime and dirt.

Same thing happened to one of my rear wheel cylinders on my 68 C10. Fluid leaked out of the wheel cylinder but never left the drum but sure coated everything in it with brake fluid. They can leak slowly.

[BluTrukker]

Thanks for all the advice. gmsee, what year booster would work? I'll let you all know what I find when I get into it. Too many home improvment projects right now. When the snow starts flying I will probably have time to fix it and do some upgrades I have been planning.