1972 K10 Brake System Issues

[k10klub]

Good morning all, I am looking for a little input on my brake system, thanks in advance.

I have a 1972 K10, 4-inch lift & 35 inch tires, all factory-style brake components from Auto Zone, except for ORD stainless steel extended brake lines to account for 4-inch lift. I replaced the master cylinder, booster, calipers, wheel cylinders, rotors, drums, pads, shoes, and rubber lines about 5-6 years ago (all at once), and have driven about 25k miles since then.

2 things aren’t quite right with my system:

1. The pedal feels like the vacuum power assist is not working, more like I have manual brakes, always has ever since I got the truck, before & after I replaced the master cylinder, before & after lift & tires, and regardless of how many times I bleed the brakes.
   
   
2. Driving home from work yesterday there was a guy taking too long to make a left turn and I had to jam hard on the brakes, when I let off of the pedal they kept dragging like I still had my foot on it for a second or two.
   

Any tips are greatly appreciated

 

[Clark75K5]

I put a rebuilt booster in a 1970 K20 and it failed on me in less than a year so don't rule that out. Does the idle change when you step on the brake with it stopped, and/or hear a whooshing sound?

 

[Wes Harden]

Hard linings will act like a bad booster. So will a hardened drum.
Auto Zone brake lining material esp the lower quality stuff has always been suspect to me.
If it's been awhile since the rears were adjusted, a shoe could have gotten hung up for a sec or 2.
Possible a caliper didn't want to slide back after the hard brake episode.
Check the metal bushings and lube them with siliglide. Inspect the rings in the caliper what the bushings ride on.
Clean any rust on caliper and hanger where they touch.

Good luck let us know what you find

 

[Fordum]

Old style quick test for a booster.
Turn engine off, press and release brakes several times to bleed off any residual vacuum. Let brake pedal sit for a few seconds, then press firmly and hold pressure. No pumping.
Crank engine while holding strong pressure on brake pedal.
When the engine starts running, the pedal should drop a short distance indicating the booster has kicked in.
Having the pedal drop does not totally eliminate a possible weak or leaky booster, but no drop at all is a definite indication of a booster problem.

 

[diesel4me]

A blockage in any of the metal lines or rubber hoses can cause a very hard pedal,but little braking effect ..

I've seen rubber hoses swell shut inside that were less than 5 years old..plugged solid!..a dented or kinked metal line will have the same effect..usually though,only one goes bad,and it'll make the vehicle pull hard to the side that has the "good" hose ..the rear rubber hose can plug up and you'll lose both rear wheel brakes..but the pedal will feel firm ,like nothing is wrong..

 

[k10klub]

Update:

1. Checked the vacuum line and it seems like I am getting vacuum, unplugged it from the plastic elbow fitting on the booster and I get a loud sucking sound. Also, the idle will drop and the engine dies when I do this.
2. Idle does not seem to change and, no, I do not get a woosh sound when I step on the pedal.