The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1967 - 1972 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 01-08-2019, 06:21 PM   #1
ChevyGearHeads
Registered User
 
Join Date: Jul 2010
Location: Anne Arundel County, MD
Posts: 108
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.
__________________
Paul
'68 C10 327/TH350
LWB
ChevyGearHeads is offline   Reply With Quote
Old 01-08-2019, 06:25 PM   #2
68Stepbed
Registered User
 
68Stepbed's Avatar
 
Join Date: Mar 2005
Location: 10-Uh-See
Posts: 5,609
Re: All drums and no hope.

Sounds like bad wheel cylinders.
__________________
Matt

68 C10 stepside, LS1/700R4, TCI Engineering suspension system
68Stepbed is offline   Reply With Quote
Old 01-08-2019, 06:28 PM   #3
demian5
Registered User
 
demian5's Avatar
 
Join Date: Aug 2016
Location: Lake Forest, CA
Posts: 2,177
Re: All drums and no hope.

Quote:
Originally Posted by 68Stepbed View Post
Sounds like bad wheel cylinders.
Sounds like you did miss something. List out what you replaced with something new.
__________________
"Work hard, use your vacation days."
1970 C15 GMC Long Bed
1986 C20 Scottsdale
1983 K2500 Sierra Classic Suburban 6.2
Instagram: C10sofOC
demian5 is offline   Reply With Quote
Old 01-08-2019, 06:32 PM   #4
68Gold/white
Registered User
 
Join Date: Sep 2011
Location: Ark City, Kansas
Posts: 3,263
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...
68Gold/white is offline   Reply With Quote
Old 01-08-2019, 06:41 PM   #5
ChevyGearHeads
Registered User
 
Join Date: Jul 2010
Location: Anne Arundel County, MD
Posts: 108
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?
__________________
Paul
'68 C10 327/TH350
LWB
ChevyGearHeads is offline   Reply With Quote
Old 01-08-2019, 09:26 PM   #6
WorkinLonghorn
Senior Member
 
WorkinLonghorn's Avatar
 
Join Date: Dec 2006
Location: Studio City, Calif.
Posts: 2,855
Re: All drums and no hope.

Quote:
Originally Posted by 68Gold/white View Post
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^^^^
__________________
'69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, 2nd owner, Work-Truck supreme. Best $300 I ever spent.
WorkinLonghorn is offline   Reply With Quote
Old 01-08-2019, 10:11 PM   #7
burnin oil
Registered User
 
Join Date: Jan 2013
Location: Eastern TN
Posts: 1,919
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.
burnin oil is offline   Reply With Quote
Old 01-09-2019, 11:30 AM   #8
68Gold/white
Registered User
 
Join Date: Sep 2011
Location: Ark City, Kansas
Posts: 3,263
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!!!
68Gold/white is offline   Reply With Quote
Old 01-09-2019, 11:38 AM   #9
ChevyGearHeads
Registered User
 
Join Date: Jul 2010
Location: Anne Arundel County, MD
Posts: 108
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.
__________________
Paul
'68 C10 327/TH350
LWB
ChevyGearHeads is offline   Reply With Quote
Old 01-09-2019, 11:51 AM   #10
ChevyGearHeads
Registered User
 
Join Date: Jul 2010
Location: Anne Arundel County, MD
Posts: 108
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.
__________________
Paul
'68 C10 327/TH350
LWB
ChevyGearHeads is offline   Reply With Quote
Old 01-09-2019, 01:04 PM   #11
randy500
Account Suspended
 
Join Date: Jul 2016
Location: Tacoma, WA
Posts: 6,873
Re: All drums and no hope.

Standard brake procedure....adjust the shoes! You will never get a good pedal until it’s done properly. It’s 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.
randy500 is offline   Reply With Quote
Old 01-09-2019, 02:59 PM   #12
RustyBucket
Registered User
 
RustyBucket's Avatar
 
Join Date: Jul 2009
Location: Space Coast, Fl.
Posts: 1,050
Re: All drums and no hope.

MAYBE your new master cylinder is enough different that the push rod is a little short.
__________________
Dad always said, "Son, WISH IN ONE HAND, and ......."
--------------------------------------
--------------------------------------
Current toy trucks:
'71 GMC 1500 SUPER CUSTOM short/step, orig. dk. blue, 350/700r, ps,pb, A/C
'72 Blazer 2wd, ochre & white, 454, tremecTKO 500 5spd. ps, pb, A/C, tilt

Last 10yrs of hobby vehicles, had a FEW more in the 50yrs. before these:
'66 Plymouth Belvedere City of Miami cop car clone.
'70 Nova 406"sb, 13.5-1, solid roller, Brodix, p.glide/t.brake, back halved, 9" Ford, spool 4.88, cage,ladder bar/coilover, 10.5 tire....... SOLD!!
'67 C10 short/step side mount spare -- SOLD!!
'72 Jimmy 2wd, 350/350, ps, pb, fun driver, lots of bondo & a shiny red paint job..... SOLD!!
'69 Nova 350, 4spd, A/C, ps, p.b, ...SOLD!!
RustyBucket is offline   Reply With Quote
Old 01-09-2019, 03:11 PM   #13
cypressbog
Go Pack Go!
 
Join Date: Nov 2005
Location: Green Bay
Posts: 2,669
Re: All drums and no hope.

Make sure the shoes are adjusted then bleed brakes. First RR then LR, then RF and finally LF.
cypressbog is offline   Reply With Quote
Old 01-09-2019, 03:28 PM   #14
rpmerf
Registered User
 
rpmerf's Avatar
 
Join Date: Feb 2011
Location: Parkville, MD
Posts: 1,024
Re: All drums and no hope.

Quote:
Originally Posted by ChevyGearHeads View Post
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
__________________
1970 C20 Custom Camper - 350, TH350
1997 GMC Suburban
1994 Acura Integra GSR
1987 Dodge Daytona Shelby Z
rpmerf is offline   Reply With Quote
Reply

Bookmarks

Tags
1968 c10, 1968 chevy truck, brakes, drum brakes, proportioning valve

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 06:21 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com