My breaks are going to the floor with very little resistance. Couldn't lock em if I had to. The lines and cylinders are not leaking and the power booster was bypassed by a previous owner. Any ideas?

/// It is your Master Cylinder. It does not have to leak to be bad. There is a piston that seals to the cylinder walls and wears out. The rubber fails from wear.

If the rear drums were way out of adjustment then the pedal would be low but firm. I am assuming rear drums on your 68. You could improve the pedal hieght by adjusting the rear brakes if that were the case.

Master cylinders are a blind bore. Compare it to wheel cylinders. They are difficult to rebuild, not for skill, but because it is difficult to inspect the bore for pitting. There are shops listed in Hemmings Motor News that will rebore and reline the bore with stainless steel.

Couple quick things to check...

Does your handbrake work?

If so, does the pedal feel better if you have the handbrake partially on?

If so, adjust and/or replace the rear brake shoes.

(having the handbrake on essentially does the same thing as having the brakes adjusted too tight...don't drive with it on, but its a good way to check)

Does the pedal feel better if you pump it up a few times?

If so, bleed the brakes.

If neither of these tests helps, you probably have some problems in the hydrolics somewhere...but I put my money on a rear brake adjustment.

Of course, check your front pads while you are at it, and the brake fluid level as well.

Good luck, and be safe! Get 'em working.

-Matt B

65 1800s beater (but on the road and running well again!)

71 145s

53 XK120

68 GMC 1/2 ton beater.

Matt, I think you are probably right. It feels better with the emergency brake slightly engaged. The hand brake works fine. It puzzled me as i could find no leakage and the drums in the rear when turned have that gritty sound/slight resistance at one point in the revolution but it must be dirt or grit in the drums I think. I have to bounce this stuff off of others to get some idea of where I am LOL. Thanks. Appreciate the quick response.

Make sure the handbrake was properly adjusted, slacken the cables right off, adjust the shoes, then last of all set the cable so you get about 6 clicks on the ratchet.

Get someone to observe the hoses as the pedal is pressed, you may have a bulging hose

Regards

Master cylinder. Pull back the rubber boot poking into the cabin at the back of the master and I'll bet it is weeping fluid.

Regards

Thanks for your quick response. Much appreciated. I neglected to say the master cylinder is dry as a bone in the cab as well as under the hood.