The 1947 - Present Chevrolet & GMC Truck Message Board Network

The 1947 - Present Chevrolet & GMC Truck Message Board Network (http://67-72chevytrucks.com/vboard/index.php)
-   The 1967 - 1972 Chevrolet & GMC Pickups Message Board (http://67-72chevytrucks.com/vboard/forumdisplay.php?f=3)
-   -   All drums and no hope. (http://67-72chevytrucks.com/vboard/showthread.php?t=779174)

ChevyGearHeads 01-08-2019 06:21 PM

All drums and no hope.
 
I have a '68 C10 with an all manual drum set-up. I have tore down and replaced every piece of the system (including two master cylinders) and I get some pressure but not for long and the pedal works its way to the floor. The only existing original part is the proportioning/combination valve/distribution block. I have tried to bleed this truck about 4 times for hours on end with the same bleak result. Any guidance would be great. :smoke:

68Stepbed 01-08-2019 06:25 PM

Re: All drums and no hope.
 
Sounds like bad wheel cylinders.

demian5 01-08-2019 06:28 PM

Re: All drums and no hope.
 
Quote:

Originally Posted by 68Stepbed (Post 8439404)
Sounds like bad wheel cylinders.

Sounds like you did miss something. List out what you replaced with something new.

68Gold/white 01-08-2019 06:32 PM

Re: All drums and no hope.
 
You need to make darn sure the brakes are adjusted. If in doubt adjust the shoes to where the drum/spindle or axle is tight, and barely turns. You can back the shoes off later....to operate vehicle...

Fill the M/cylinder, let each wheel gravity bleed, one wheel at a time, of course do both rears or both fronts together...THEN have someone help you pressure bleed the brakes...DO NOT LET THE MASTER CYLINDER RUN DRY!!! the master cylinder needs to be bench bled first...

I use 1/4" I.D. clear vinyl tubing, I loop it a foot or two above the bleeder screw, so I can wattch for fluid and/or bubbles...I use an empty 16 oz or larger plastic pop bottle to catch the excess fluid. I drill a hole just slightyl smaller than the OD of the hose, so the tubing stays in the bottle. and you need another small hole in the bottle cap for pressure relief...

ChevyGearHeads 01-08-2019 06:41 PM

Re: All drums and no hope.
 
-Master Cylinder (bench bled twice)
-Both 3/16th lines to the front.
-Both front hoses.
- All 4 wheel cylinders, shoes, springs, drums, self-adjusters
- 5 foot section of line going to the rear hose.
- Rear hose
- Both 3/16th lines going to the rear.

I seem to keep getting air in the system so I installed 4 speed bleeders.
The pedal will start to get firm and just go away.
I can hear the shoes hitting the drums..both front wheels you can hear the shoes dragging the drum very slightly. I never considered adjusting them?

WorkinLonghorn 01-08-2019 09:26 PM

Re: All drums and no hope.
 
Quote:

Originally Posted by 68Gold/white (Post 8439408)
You need to make darn sure the brakes are adjusted. If in doubt adjust the shoes to where the drum/spindle or axle is tight, and barely turns. You can back the shoes off later....to operate vehicle...

^^^^ This^^^^

burnin oil 01-08-2019 10:11 PM

Re: All drums and no hope.
 
The others are on the track. One more thing you may try is breaking loose the lines and reseating them. I have seen some where they didnt 100% line up and leaked. Reseating the line squarely and retightening solved the issue.

If you do need to replace the proportioning valve I would suggest digging through Summit Racing. They are one of the few places that really stock them and have many combinations/options available. I have an old Dodge 2500 that I fought the brakes on and replaced it all. Brakes were still crap and you never knew if it would stop. I ended up getting the proportioning valve for a 70s chevy and swapped it in. That truck stopped in half the distance as it did new! It is amazing how much fluid can actually bypass inside those things.

68Gold/white 01-09-2019 11:30 AM

Re: All drums and no hope.
 
Remove the 4 speed bleeders, and install the regular bleeders, then bleed brakes as in post 4, after adjusting shoes...

With shoes that are at least a little out of adjustment, the pedal can feel exactly like what you have...

The pistons in the wheel cylinder move very little to make the shoes contact the drums. It's a fine line deal. I am sure you are very close to making the deal done!!!

Are the drums new??? or in spec??? If they are out of spec, it will contribute to the problem...slightly...

I hate drum brakes, especially on the front!!!

ChevyGearHeads 01-09-2019 11:38 AM

Re: All drums and no hope.
 
Re: 68Gold/White

The drums are brand new and I'm assuming in spec.
I haven't attempted to adjust them because I figured they would self adjust?
The shoes just barely contact the drum with the brakes disengaged.

ChevyGearHeads 01-09-2019 11:51 AM

Re: All drums and no hope.
 
Can the distribution block be causing an issue?
they seem to be surrounded by mystery if its not a disc/drum setup.

randy500 01-09-2019 01:04 PM

Re: All drums and no hope.
 
Standard brake procedure....adjust the shoes! You will never get a good pedal until itís done properly. Itís loose shoes you can get a pedal for a short while and it will bleed down to no pedal.

Your problem is not the distribution block.

RustyBucket 01-09-2019 02:59 PM

Re: All drums and no hope.
 
MAYBE your new master cylinder is enough different that the push rod is a little short.

cypressbog 01-09-2019 03:11 PM

Re: All drums and no hope.
 
Make sure the shoes are adjusted then bleed brakes. First RR then LR, then RF and finally LF.

rpmerf 01-09-2019 03:28 PM

Re: All drums and no hope.
 
Quote:

Originally Posted by ChevyGearHeads (Post 8439860)
I haven't attempted to adjust them because I figured they would self adjust?

The brakes self adjust when you firmly apply the brakes while the vehicle is moving backwards.

After checking adjustment, I would check over every junction and wheel cylinder to look for any signs of leakage. Check rubber lines also.

I've had issues with air being sucked around the bleeders while attempting to bleed. You can either wrap the bleeders in teflon tape, or:
Start pressing the pedal
Open the bleeder
Press the pedal down to about 75%
Close the bleeder
Release the pedal


All times are GMT -4. The time now is 02:58 PM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Copyright 1997-2013 67-72chevytrucks.com