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Hydroboost brakes not unloading

broncotime

Bronco Guru
Joined
Jun 30, 2003
Messages
1,186
Loc.
Grapevine, Texas
Anyone have a problem where the calipers don't unlaod all the way when the brake is released? Truck stops fine, but front brake pads still squeezing the rotor even after the petal is released. If I jack up the front wheel, I can just barely get it to spin. I've got front disks (full size D44 from a '79 Bronco).

Not sure what to check first, any thoughts?

Thanks
 

lowpressure

Full Member
Joined
Jul 28, 2010
Messages
342
Loc.
Shreveport, LA
both sides or just one? the big bronco and late 70s 150s had a recurring problem with the soft liners inside the brake hoses so if you have the problem on only one side u may have a flutter inside one ...........if its both sides then both the master and hyro assist can cause it .....make sure the master's rod is returning to the full release position and if it is then your probably gonna have to take a close look at your assist unit.
 

brbuilder

Jr. Member
Joined
Aug 19, 2007
Messages
135
After I completed my coversion and after several test runs in the neighborhood took it for a ride. Worked fine for about 5 miles then it was like I was dragging an anchor. The push rod was a little long causing the brakes to not release. Added a couple washers as spacers between the MC and HB. Fixed the problem. Might be worth a try.
 

66fora69er

Sr. Member
Joined
Dec 9, 2006
Messages
478
After braking I have to lift the pedal with my toe/shoe (only slightly) or the pads dont fully disengage. I will try that washer idea. Thanks for the idea;D
 
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broncotime

broncotime

Bronco Guru
Joined
Jun 30, 2003
Messages
1,186
Loc.
Grapevine, Texas
both sides or just one? the big bronco and late 70s 150s had a recurring problem with the soft liners inside the brake hoses so if you have the problem on only one side u may have a flutter inside one ...........if its both sides then both the master and hyro assist can cause it .....make sure the master's rod is returning to the full release position and if it is then your probably gonna have to take a close look at your assist unit.
Both sides are tight, so I'll start looking up at the hydroboost end.
 
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broncotime

broncotime

Bronco Guru
Joined
Jun 30, 2003
Messages
1,186
Loc.
Grapevine, Texas
Is this a new installation? Did it ever work correctly?

What master cylinder are you using?
It's not a new installation, but was done by a previous owner so I have no idea if it ever worked right. I've had the truck a year, but it sat most of that time in my gargage while I fixed a few things that had to be done like getting rid of the top loader tranny for an NP435, putting on the twin sticks, getting rid of the stock suspension w/ lift blocks in the rear for WH 3.5 inch leafs, adding shocks, and so on, and so on.

I will dig through the paperwork to see if the PO left any indication of what MC they used on the brakes, but I think I will try the washer/spacer idea first as that is easy to do and see if it makes any difference.
 

rainer73

Jr. Member
Joined
Oct 8, 2008
Messages
55
Loc.
Deer Park,Texas
Glen,
I had the same issue on both of my hydroboost conversions. I had to
shorten the push rod about a 1/16 inch to allow the front brakes to fully release. See you in Hot Springs!
Doug
 

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broncotime

broncotime

Bronco Guru
Joined
Jun 30, 2003
Messages
1,186
Loc.
Grapevine, Texas
Glen,
I had the same issue on both of my hydroboost conversions. I had to
shorten the push rod about a 1/16 inch to allow the front brakes to fully release. See you in Hot Springs!
Doug
I'll try a 1/16th inch spacer between the MC and the hydroboost and if that fixes it, then I'll shorten the rod (also suggested by a previous poster). I can't wait for OCBR, I'll see you there. The yellow truck is staying home this year and I'll be banging up the blue/white rig.
 
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broncotime

broncotime

Bronco Guru
Joined
Jun 30, 2003
Messages
1,186
Loc.
Grapevine, Texas
Okay, I added the spacers and they are still not unloading, so I don't think that is my problem. I printed out the hose routing diagram from PSC's website (double ended ram w/ hydroboost) so I can double check the hose routing. When I turn off the engine, the brakes unload so I think something in the hydroboost is causing my problem. I've got an angle bracket and a hydroboost unit I picked up for my other truck, so maybe I'll throw those on.

Since I wheeled the truck at OCBR I probably need to repack the front hubs with high temp grease as they got pretty warm from the constant brake pressure.
 
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