Squishy Brakes
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5th Wheeling
Joined: Aug 2017
Posts: 36
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Squishy Brakes
So got my 64 F100 axel swap I just completed so I can convert to 4WD
Rebuilt a Dana 44 closed knuckle and Dana 60 with drum brakes, new drums, shoes, wheel cylinders and mostly new brake line for the truck.(just two original hard lines all new hydraulic hoses) New master cylinder too. I have bleed about 4 liters of break fluid through this now and pedal is still squishy and can’t stop worth crap. Had zero issues before the axel swaps. No visual leaks or seeping anywhere in the lines. All the wheel adjuster screws are extended so they’re slight contact with the drums and shoes Did the tropical two man brake bleeding, pedal down, open zyrt, close zyrt, pedal up and repeat.
Bought a pneumatic bleeder just to try it and still squishy brakes.
if I pump the brakes they get slightly stiffer but still not optimal nor safe for the roads.
Any help guys?
Rebuilt a Dana 44 closed knuckle and Dana 60 with drum brakes, new drums, shoes, wheel cylinders and mostly new brake line for the truck.(just two original hard lines all new hydraulic hoses) New master cylinder too. I have bleed about 4 liters of break fluid through this now and pedal is still squishy and can’t stop worth crap. Had zero issues before the axel swaps. No visual leaks or seeping anywhere in the lines. All the wheel adjuster screws are extended so they’re slight contact with the drums and shoes Did the tropical two man brake bleeding, pedal down, open zyrt, close zyrt, pedal up and repeat.
Bought a pneumatic bleeder just to try it and still squishy brakes.
if I pump the brakes they get slightly stiffer but still not optimal nor safe for the roads.
Any help guys?
Fleet Mechanic
Joined: Dec 2016
Posts: 1,261
Likes: 714
Assuming all was installed and bled properly, I'd pull the drums to be sure none of the cylinders are leaking as it may not be obvious from the outside (provided you didn't do that already) If all ok my next suspect would be the mc. Just because it's new doesn't mean it's good. Maybe swap your old one back on.
Tony
Tony
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5th Wheeling
Joined: Aug 2017
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Assuming all was installed and bled properly, I'd pull the drums to be sure none of the cylinders are leaking as it may not be obvious from the outside (provided you didn't do that already) If all ok my next suspect would be the mc. Just because it's new doesn't mean it's good. Maybe swap your old one back on.
Tony
Tony
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5th Wheeling
Joined: Aug 2017
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to my knowledge you adjust the shoes until there is light friction so turning the drum/wheel there is light resistance. Am I mistaken?
Laughing Gas
Joined: Sep 2012
Posts: 860
Likes: 13
From: Asheville, NC
I have always left the shoes a bit loose; bled the brakes; then adjusted the shoes out to get light drag then loosen back up a hair. It is also difficult to get the air out of a new master cylinder. I always bench bleed prior to install.
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5th Wheeling
Joined: Aug 2017
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If you have the shoes all the way against the drum; could it be possible there isn’t enough movement in the wheel cylinders to really push the air out?
I have always left the shoes a bit loose; bled the brakes; then adjusted the shoes out to get light drag then loosen back up a hair. It is also difficult to get the air out of a new master cylinder. I always bench bleed prior to install.
I have always left the shoes a bit loose; bled the brakes; then adjusted the shoes out to get light drag then loosen back up a hair. It is also difficult to get the air out of a new master cylinder. I always bench bleed prior to install.
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Laughing Gas
Joined: Sep 2012
Posts: 860
Likes: 13
From: Asheville, NC
Well, you got a lot of bases covered. I will now concur with the member mentioning bad Master Cylinder. I have bought several MCs over the years that were faulty.
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5th Wheeling
Joined: Aug 2017
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okay I just popped off all four drums and no leaks and saw the cylinders operating. I will take the new MC in tomorrow and get another one. If it isn’t then I’m not sure what to do
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
I've had better luck running the adjusters all the way out (tight) prior to bleeding, seems like the wheel cylinders get a better fill. Close everything up and pump the pedal a few times to center the shoes and take up any slop or clearance. Then back the adjusters off till there is still a light drag when spinning the wheel.
Tuned
Joined: Oct 2011
Posts: 312
Likes: 12
From: Warsaw
Are the flexable brake lines in front new or used? The master cylinder displaces a fixed amount of fluid and if the flex lines are old and expanding under pressure you'll get a weak pedal. Happened to me years ago and now I only use lines with a braided cover.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Yeah any mechanical slop in the rear drum assembly seems to result in a low, squishy pedal that is a lot like air in the lines. Run 'em up all the way tight (adjusters) till they lock, and bleed them that way. Close the blleeder screws, pump the brakes several times to center the shoes, Then back the adjusters off till a "light" drag when spinning the wheel. Take it for a short drive around the block and braking a few times, then check for proper adjustment again manually. Without that good close initial manual adjustment, the "self adjusters" will NEVER work while backing up.
Cargo Master
Joined: Jan 2016
Posts: 2,674
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Probably a brake shoe adjustment issue like already discussed.
If you have a brake light switch in your master cylinder, remember to burp it. Also, nice to have the truck's rear equal or lower than front of truck to help get the last bubble out of the master cylinder.
If you have a brake light switch in your master cylinder, remember to burp it. Also, nice to have the truck's rear equal or lower than front of truck to help get the last bubble out of the master cylinder.