The Stovebolt Page Forums Home | FAQ | Forum | Swap Meet | Gallery | Tech Tips | Events | Features | Search | Hoo-Ya Shop
Helping out ...


EVENTS

Check in for status!

Jump over to the Events Forum, to post events -- new ones or the ones we have been enjoying for some time.
Look to see what's been cancelled or postponed.

Encourage one another!

Stovebolt Site Search
 
Old Truck Calendars
Months of truck photos!
Nothing like an old truck calendar

Stovebolt Calendars

Check for details!


Who's Online Now
16 members (59 fleet, 48bigtrucks, 52Carl, Achipmunk, 3800GUY, 4 invisible), 91 guests, and 3 robots.
Key: Admin, Global Mod, Mod
Forum Statistics
Forums50
Topics119,477
Posts956,640
Members43,409
Most Online1,229
Jan 21st, 2020
Image Posting Policy
Previous Thread
Next Thread
Print Thread
Page 1 of 4 1 2 3 4
Brakes drag after 10 minutes.
#1356995 Sat Apr 25 2020 01:42 AM
Joined: Sep 2011
Posts: 1,961
L
Lugnutz Offline OP
Shop Shark
Right now I’m so frustrated I can’t think straight.
I just finished installing a new dual brake master cylinder and booster in my 1965C 10 I/2 ton. I was previously using a 1995 Blazer MC and brake booster. The brakes worked fine but I noticed that after 10 or 15 minutes of driving, the brakes would begin to drag. You could let off of the brake pedal on a slight incline and the truck would not coast backwards.
This new master cylinder and brake booster are doing the EXACT SAME THING. My 63 C10 has the exact same MC and brake booster with front disc and rear drums and I have absolutely no problems there.
I am certain that the brake pushrod is allowing the master cylinder plunger to completely return to the home position.
My next thought is that the pistons in the front disc brake calipers are not moving correctly. If this is true, then they do not pull the brake pads completely off the rotor as they should.
Anyone have thoughts on this matter?

Last edited by Lugnutz; Sat Apr 25 2020 01:43 AM.
Re: Brakes drag after 10 minutes.
Lugnutz #1356998 Sat Apr 25 2020 01:53 AM
Joined: Feb 2004
Posts: 20,351
H
Boltergeist
Once the brakes start to drag, stop the truck, chock a wheel front and rear, and loosen the bleeder screws on the calipers. It's possible you're trapping fluid in one or both calipers due to a flex line collapsing inside. If you get a spurt of fluid and the brake drag releases, replace the flex line on the offending side, or both of them if that hasn't been done recently. I've seen several examples of that problem over several years, one of which got so bad a transmission failed because the car owner was too stubborn to stop and call for a tow truck, and kept on driving with the brakes dragging.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Brakes drag after 10 minutes.
Lugnutz #1357002 Sat Apr 25 2020 02:01 AM
Joined: Sep 2011
Posts: 1,961
L
Lugnutz Offline OP
Shop Shark
Thanks for your comment Jerry.
So if I understand you correctly, when pressure in the brake lines goes to zero (when I let off of the brake pedal), the flexible brake hose may be collapsing and preventing the fluid behind the caliper piston from going to zero. Right?

Re: Brakes drag after 10 minutes.
Lugnutz #1357005 Sat Apr 25 2020 02:22 AM
Joined: Feb 2004
Posts: 20,351
H
Boltergeist
Yep, I've seen it happen frequently. If the caliper doesn't release when the bleeder is opened and the wheel still drags (jack up the wheel to check that) then you have a sticky piston in the caliper.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Brakes drag after 10 minutes.
Lugnutz #1357018 Sat Apr 25 2020 02:59 AM
Joined: Apr 2005
Posts: 2,527
C
Shop Shark
Someone PLEASE come up with an answer for this. My 37 Buick worked fine for 30 years with a drum-drum dual master cylinder and power booster. Got caught in a dicey situation in Kansas City during a monsoon where the drums were under water so decided to put discs on the front. Put the disc-drum dual mc on and even the hubcaps are hot to the touch after ten miles. Decided the supposed to be 10# drum and 2# disc residual pressure seats in the mc were wrong so to test I put the old mc back on after drilling through the flare seats to eliminate ANY residual pressure. Same thing so replaced new hoses that came with the disc kit with two more new hoses. Same thing. Took some 3/16 steel line with a double loop and replaced rubber line for a (very) temporary test. Same thing. The link from pedal to booster is floppy loose when spring retracts pedal and have shortened the rod from booster to mc till the pedal has gone from near full height to 1.5 iches off the floor. When the car stops as soon as you leave up on the gas I jump out with a 10mm wrench and crack the bleeders which makes it completely free. Summary: NO rubber lines, NO residual pressure valves, rods NOT touching the booster or mc, what's happening? Oh yeah, used spare mc cap with two large vent holes in it for testing. Drove into shop while nearly sliding front wheels and cracked left bleeder--wheel spun free but right side was still nearly locked.


Evan
Re: Brakes drag after 10 minutes.
Lugnutz #1357023 Sat Apr 25 2020 03:28 AM
Joined: Feb 2004
Posts: 20,351
H
Boltergeist
Evan, have you tried swapping to a different caliper on the brake that drags? What's supposed to happen when the pressure releases after a brake application is the square O ring that seals the fluid is also supposed to retract the piston a few thousandths when it returns to "square" after being distorted slightly when the brakes are applied. At times, I have had to do some serious honing of the caliper bore so the piston is a sloppy loose fit. Otherwise, the piston can't retract enough to keep the pads from dragging on the disc. Back when Ford was using plastic caliper pistons, it wasn't a question of IF, but WHEN the brakes would drag. I can't count the number of chrome plated metal caliper pistons I swapped out on early 1980's Ford brakes!
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Brakes drag after 10 minutes.
Lugnutz #1357044 Sat Apr 25 2020 12:55 PM
Joined: Jan 2016
Posts: 557
S
Shop Shark
Along with the already mentioned fixes.........debris in the master cylinder that is blocking the return port with cause brake drag.

Picture is dual master so it shows two circuits.

Attached Files
Re: Brakes drag after 10 minutes.
Lugnutz #1357065 Sat Apr 25 2020 02:43 PM
Joined: Sep 2011
Posts: 1,961
L
Lugnutz Offline OP
Shop Shark
UPDATE:
I just drove the truck for 10 minutes and the brakes have gotten really tight. I drove into the shop and put it up on the lift. The rear wheels turn freely with the transmission in neutral. No drag.
The front wheels are so tight I cannot turn them by hand.
So one possibility is simultaneous collapse in both front brake hoses.
The second possibility is that the caliper pistons are not moving smoothly.

Re: Brakes drag after 10 minutes.
Lugnutz #1357068 Sat Apr 25 2020 02:48 PM
Joined: Mar 2019
Posts: 735
G
Shop Shark
Replace all in front, calipers and hoses. Or unless theres a fluid issue of sorts from the master cylinder?

Re: Brakes drag after 10 minutes.
Lugnutz #1357070 Sat Apr 25 2020 02:52 PM
Joined: Feb 2004
Posts: 20,351
H
Boltergeist
Did you try opening the bleeder screws to see if the drag goes away? That's the best way to tell the difference in restricted hoses or sticky calipers.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Page 1 of 4 1 2 3 4

Moderated by  SWEET 

Link Copied to Clipboard
Home | FAQ | Forum | Swap Meet | Gallery | Tech Tips | Events | Features | Search | Hoo-Ya Shop
Powered by UBB.threads™ PHP Forum Software 7.7.4