Brake Issues... Help! ASAP
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Fleet Mechanic
Joined: Jun 2011
Posts: 1,804
Likes: 5
From: Southern California
Brake Issues... Help! ASAP
Ok so its a 1974 highboy. I have a hydratech hydroboost system and it has worked flawlessly for 2 years.
I just installed new leaf springs and my Dana 60 kingpin axle in front, and a GM corporate 14 bolt full floater rear.
Brand New Calipers and 3AN stainless lines to replace factory rubber in front
Brand New wheel cylinders and hardline (on axle) in rear with a 32" 3AN stainless braid line going from axle to the frame.
The master cylinder never drained when I installed the axles. I bleed the brakes properly. 4 quarts of fluid later I have a pedal that feels a bit stiff but doesn't pump up and get rock hard after 3 or 4 pumps with the engine off. With the engine on the pedal stays at the floor and raises slowly when I push the brakes.
There is no air coming out of the lines anymore. So I replaced the master cylinder and bench bleed it first. Re bleed the whole system. Still same thing. The front brakes apply slightly but the rears don't at all and I have the shoes really tight so it shouldn't take much to apply them....
What am I missing?????
I just installed new leaf springs and my Dana 60 kingpin axle in front, and a GM corporate 14 bolt full floater rear.
Brand New Calipers and 3AN stainless lines to replace factory rubber in front
Brand New wheel cylinders and hardline (on axle) in rear with a 32" 3AN stainless braid line going from axle to the frame.
The master cylinder never drained when I installed the axles. I bleed the brakes properly. 4 quarts of fluid later I have a pedal that feels a bit stiff but doesn't pump up and get rock hard after 3 or 4 pumps with the engine off. With the engine on the pedal stays at the floor and raises slowly when I push the brakes.
There is no air coming out of the lines anymore. So I replaced the master cylinder and bench bleed it first. Re bleed the whole system. Still same thing. The front brakes apply slightly but the rears don't at all and I have the shoes really tight so it shouldn't take much to apply them....
What am I missing?????
Thread Starter
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Fleet Mechanic
Joined: Jun 2011
Posts: 1,804
Likes: 5
From: Southern California
According to hydratech, the hydroboost wont work if I cant get a solid manual brake pedal. So I need to find out why I cant get a manual pedal first. It worked fine 2 days ago before I axle swapped so I know the unit is good. First thing in the AM I am going to stick a plug in the rear brake port on the master cylinder and see if I can get a firm pedal. If I do that means the issues is 100% the rears. And then im back to figuring out why.
http://shop.broncograveyard.com/mobi...uctinfo/22519/
I thought the issue might have been this so I stuck the bleeding tool in and even with no pressure regulation I can't get a firm pedal nor can I get the rear brakes to stop even the tire when I turn it by hand.
http://shop.broncograveyard.com/mobi...uctinfo/22519/
I thought the issue might have been this so I stuck the bleeding tool in and even with no pressure regulation I can't get a firm pedal nor can I get the rear brakes to stop even the tire when I turn it by hand.
Logistics Pro
Joined: Mar 2009
Posts: 4,857
Likes: 609
From: Minnesota
When you changed out the front axle what was previously there? Was it drum brakes or single piston calipers? Is the new axle dual piston calipers? If you increased the amount of fluid needed to operate the brake system , you may need to change out your master cylinder to get the correct volume needed now.
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