Ken K
I'm Awesome
With the vehicle running, step on the brake pedal until it get to a normal feel of stiffness. Hold it there, then shut off the engine. Slowly release and work the pedal about 3 to 4 times. If it does NOT go lower, you have a booster issue. If it drops even more and then firms up, the booster is ok. This is just a quick check as you are removing the vacuum from the booster that provides assist. Pedal is either good or not, but part of diagnostics, is all hydraulic and relies on shoe / drum and pad / piston movement. They other reason is mechanical.
You asked about the rear drums adjustment. If the drums have not been resurfaced, they will have a lip on the inside edge and will be hard to remove when adjusted correctly. Either way, machined or not, when installed, put two lug nuts on snug to hold it against the axle, ratchet the adjuster while rotating the drum. When you get a decent dragging noise, go a little more until you can feel more drag, then stop. This is adjusted. This limits the travel to shoes have to move before they hit the drum. This will remove a HUGE amount of pedal travel. You can use a small pick or screwdriver to push back the adjuster lever away from the "Star" wheel, then rotate the other direction to back off. This has to be done at the same time. Not fun if you don't have practice.
Feel free to post pictures of the shoes & hardware, because there things that could be wrong there as well. The leading brake shoe is different from trailing shoe...just saying.
If your friend apply the brakes and the drum does not lock up, you will have to check the shoes mechanical. Make sure the have no grooves in the back plate where the 3 shoe "V" shape bends are on the metal part. All six pads can be dressed lightly with an angle grinder to smooth out any grooves. Shoes can hang-up and pop out making a noise while applying before the grooves get bad. If the pads are grooved bad, they will stick and not apply. Use a high temp brake grease with PTFE additive. This makes the lube good to about 580 degrees F. It was very common to replace the backing plate in the 60's and early 70's. Hardly ever done anymore, but has to be checked.
The same freedom of movement is true with the front disc. They float on pins that have to be lubricated as well with the same high temp grease. I always check for the calipers ability to slide back & forth without NO pads. This check can be made at the guide tube / pipe looking thing where the bolt goes into. It still has to be ruled out as it is a mechanical issue. Normally, it will cause un-even pad wear, pulling while braking, but rarely a low pedal.
The brake master cylinder has small holes near the back of each half or the reservoir. This hole allows fluid in to fill the master cylinders bore, for the next brake application. If the piston cannot travel far enough back, it maybe held by the booster at the pin. This pin is adjustable on many and measured with a "Go - No Go" gauge on how father it stick out of the booster. But I don't have one and neither do you. So, if you can see the back hole (Two in each reservoir) and there is no fluid movement, this could be you problem.
Note; This only occurs after replacement of one or both of these components. The push rod has to be shortened up (Or lengthen if needed) by adjustment on the push-rod pin or new part as found in a chart in a service manual. This is not easy for the un-trained eye, but will cause your problem. Look at a video for tandem brake master operation. This visual will help you understand.
Get a friend to pump the pedal slowly about 3 times and hold. First, check the rotor / drum to see if it is locked up. If yes, it locks up, do the next part. Open the bleeder screw and have your'e buddy tell you the pedal goes down more. Note if there is air bubbles coming out at this point. Continue to have your buddy hold the pedal down and close the bleeder. Air is bad, so repeat until clear.
If the drum or rotor does not lockup after 3 slow pumps, even if low pedal height, you have figure out why. Note; Pumping the pedal slowly down just prevents inducing air into the master cylinder.
The trick with clamps or needle nose vise grips will work, but I have had hoses damaged by this practice and pressure will go into the caliper or wheel cylinder and NOT release. Seen it 4 times in 30+ years, but have done it myself.
My youngest son is 34 this year, he wants instant gratification or told what to do. Be patient as it take time to respond to the needs of others. At least you appear ready to learn, as my son just wants to know what to do, but not learn.
Hope this helps. ASE Master tech since 78. Old guy!
You asked about the rear drums adjustment. If the drums have not been resurfaced, they will have a lip on the inside edge and will be hard to remove when adjusted correctly. Either way, machined or not, when installed, put two lug nuts on snug to hold it against the axle, ratchet the adjuster while rotating the drum. When you get a decent dragging noise, go a little more until you can feel more drag, then stop. This is adjusted. This limits the travel to shoes have to move before they hit the drum. This will remove a HUGE amount of pedal travel. You can use a small pick or screwdriver to push back the adjuster lever away from the "Star" wheel, then rotate the other direction to back off. This has to be done at the same time. Not fun if you don't have practice.
Feel free to post pictures of the shoes & hardware, because there things that could be wrong there as well. The leading brake shoe is different from trailing shoe...just saying.
If your friend apply the brakes and the drum does not lock up, you will have to check the shoes mechanical. Make sure the have no grooves in the back plate where the 3 shoe "V" shape bends are on the metal part. All six pads can be dressed lightly with an angle grinder to smooth out any grooves. Shoes can hang-up and pop out making a noise while applying before the grooves get bad. If the pads are grooved bad, they will stick and not apply. Use a high temp brake grease with PTFE additive. This makes the lube good to about 580 degrees F. It was very common to replace the backing plate in the 60's and early 70's. Hardly ever done anymore, but has to be checked.
The same freedom of movement is true with the front disc. They float on pins that have to be lubricated as well with the same high temp grease. I always check for the calipers ability to slide back & forth without NO pads. This check can be made at the guide tube / pipe looking thing where the bolt goes into. It still has to be ruled out as it is a mechanical issue. Normally, it will cause un-even pad wear, pulling while braking, but rarely a low pedal.
The brake master cylinder has small holes near the back of each half or the reservoir. This hole allows fluid in to fill the master cylinders bore, for the next brake application. If the piston cannot travel far enough back, it maybe held by the booster at the pin. This pin is adjustable on many and measured with a "Go - No Go" gauge on how father it stick out of the booster. But I don't have one and neither do you. So, if you can see the back hole (Two in each reservoir) and there is no fluid movement, this could be you problem.
Note; This only occurs after replacement of one or both of these components. The push rod has to be shortened up (Or lengthen if needed) by adjustment on the push-rod pin or new part as found in a chart in a service manual. This is not easy for the un-trained eye, but will cause your problem. Look at a video for tandem brake master operation. This visual will help you understand.
Get a friend to pump the pedal slowly about 3 times and hold. First, check the rotor / drum to see if it is locked up. If yes, it locks up, do the next part. Open the bleeder screw and have your'e buddy tell you the pedal goes down more. Note if there is air bubbles coming out at this point. Continue to have your buddy hold the pedal down and close the bleeder. Air is bad, so repeat until clear.
If the drum or rotor does not lockup after 3 slow pumps, even if low pedal height, you have figure out why. Note; Pumping the pedal slowly down just prevents inducing air into the master cylinder.
The trick with clamps or needle nose vise grips will work, but I have had hoses damaged by this practice and pressure will go into the caliper or wheel cylinder and NOT release. Seen it 4 times in 30+ years, but have done it myself.
My youngest son is 34 this year, he wants instant gratification or told what to do. Be patient as it take time to respond to the needs of others. At least you appear ready to learn, as my son just wants to know what to do, but not learn.
Hope this helps. ASE Master tech since 78. Old guy!
