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Brakes ???

Ohio Bronco 21

Bronco Guru
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Dec 5, 2006
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Hopefully someone has some ideas for me. I have just completed putting in an entire new brake system (lines calipers master cylinder etc) on my 66. I put front and rear DIsk Brakes with a power master cylinder (also new) I bench bleed the master before installing, I bleed the entire system. I get a good pedal when the truck is not running but when I start it and the power booster gets vacum the pedal goes all the way to the floor no resistance. I have found no leaks in the system.
I am running a junction block not a proportional valve, could not running a prop valve be the culprit?
I also had bleed the system with a vacum hand pump thinking that might do it (no luck).
ANy help is greatly appreciated.
 

fordtrucks4ever

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Do the brakes work when eingine is off or just a hard pedal? Did you bleed the lines to m/c after installing it?
 
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Ohio Bronco 21

Ohio Bronco 21

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I bench bleed the Master cylinder before installing it. Im going to check on the hard pedal when engine off.
 

Doleauto

Newbie
Joined
Feb 17, 2008
Messages
10
Sir, you could have a couple of problems. 1st I would get an assistant to help you and bleed the brake system starting with the furthest point from the master, the RR wheel, and working closer, with the engine RUNNING and the power booster operable. 2nd, I would check to make sure the actuating rod from the brake pedal TO the booster was the correct length, and 3rd, I would make sure the master is capable of delivering enough fluid to the 4 calipers. Remember, if the bore is one size on the drum brakes, it needs to be substantially larger to actuate the calipers.


Tom
 
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Ohio Bronco 21

Ohio Bronco 21

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I checked the brakes with the engine off, They work. The power master unit I am using is for updated power Brakes (disc). Im pretty sure there is very little to no air in the lines. I have bleed the system ( as above) several times. Running the engine I get no pedal. I am pretty sure the pedal rod is adjusted right as it gives me the right pedal height and feels right when the engine (ie. vacum) is off. I am wondering if a valve to the rear brakes limiting the pressure or causing more back pressure would cure it.
 

trailpsycho

Bronco Guru
Joined
Dec 11, 2003
Messages
4,856
You do have a vacuum source from theintake manifold to the brake booster, right? If you are sure that you are getting good vacuum at the booster, then try to bleed the system while running. Let us know.

If all the above checks out OK, then I would agree that there is an adjustment between the Master and the power booster that may need to be made.
 
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Ohio Bronco 21

Ohio Bronco 21

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Vacum is good from the intake to the power Booster. I cant bleed it while running because I get no pedal to pump the fluid through. I could try vacum bleeding it while running but I believ I already tried that awhile back. Hmmmmm.
 

Doleauto

Newbie
Joined
Feb 17, 2008
Messages
10
Sir----listen to what I am telling you. YOU HAVE TO BLEED THE SYSTEM WITH THE ENGINE RUNNING! Forget about the vacuum bleed at the wheels, get another person to run the pedal and have them step on the brake pedal while you open the bleeder screw furthest away from the master. Don't question it, just do it. Let them hold the pedal down for ten or fifteen seconds and then close the bleeder screw. Your system is solid full of air. Repeat this procedure until all the air bubbles are gone. When you finished the RR wheel, go to the LR and repeat, then RF, then LF. If you have just built a brake system, it is full of air. A vacuum pump is ok in its place, but not the answer for everything.
When you first start your bleed procedure, you will find almost nothing happening----don't worry, keep repeating. You will eventually hard a pedal that is hard as a rock.

Tom
 
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Ohio Bronco 21

Ohio Bronco 21

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I bled the brakes today with the engine running. I did get more air out of the system but still get the pedal going to the floor. I went around it 4 or 5 times, still no pedal ( yes I had my wife running the pedal). I may try doing it some more but it seems I have no more air comming out.
 

Revelation

Bronco Guru
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Oct 9, 2004
Messages
4,810
Yes, and be sure that she pumps it then holds the pedal untill you close the bleeder. with a whole brake system it will take a bit to get the air out, be sure to keep the Master Cyl. topped up
 

thegreatjustino

Contributor
Red Head Grease Monkey
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Just another suggestion, with the engine running and all of the bleeders closed, pump the brake pedal constantly to see if you can build up any pressure. On my motorcycle a couple of years ago I put in a new master cylinder, bench bled it, and still had to pump the system 30-40 times to build up any pressure to bleed it. With a larger system like a Bronco, you could have to pump 100 or more times to build up enough pressure if your lines are full of air.
 
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Ohio Bronco 21

Ohio Bronco 21

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Ok, I had her pump up the Brakes pretty good but I will drag her back out to the garage and go through it again several times. Ill let you know.
 
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Ohio Bronco 21

Ohio Bronco 21

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Went back and did the bleeding again. Did it 4 more times around, I get some air on each wheel except the front driver wheel, only a little the first time I open the bleeder. The pedal still hits the floor and needs to be pumped up for any brakes.
 

Doleauto

Newbie
Joined
Feb 17, 2008
Messages
10
As long as you keep getting air out of your system, that is a good thing. It doesn't take MUCH air in a system to give you a soft pedal, OR one that just won't work the brakes. Also, another indication you are getting all the air out, try turning each wheel when your wife has her foot on the brake. If you can still turn the wheel when the brake is applied, you still have air in the system. It seems like you are on the way to getting your problem resolved.
Make sure that all your connections are tight also. You don't want to "suck in" air because you have loose fittings. When your helper steps on brake, make sure no fluid is leaking anywhere.
 
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Ohio Bronco 21

Ohio Bronco 21

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Cool, thanks for the vote of confidence. when the wife pumps up the pedal and applies it it does actuate the calipers (cant turn the wheels). Pedal still goes to the floor. Man there must be alot of air in the system. I guess I just have to cycle it out. I wouldnt think I would have to bleed the system so much (8 times and counting with the truck running). I have kept checking for leaks and have not found any.
Could there be a posibility of the rear brakes needing a valve to limit the pressure seeing I dont have a Porportional valve? Thanks once again guys
 

69 Fl. Bronc

Sr. Member
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Aug 8, 2007
Messages
911
Wifes love to do this. I sugest you keep up this process until there is no more air(aslong as it takes), and then bring her out every 2 weeks, if it needs it or not. Trust me,she'll love it.
 

Doleauto

Newbie
Joined
Feb 17, 2008
Messages
10
You could have some issues with no prop valve. I am not sure what kind of "kit" you put into the truck. Did it come from a reputable manufacturer? Did it all come from one source? Send me an email directly and I will give you my phone number to call. I think it would be helpful if I talked you through some procedures.

Tom
 
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Ohio Bronco 21

Ohio Bronco 21

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cool I will PM you. I have the Master Cylinder/ Booster from the Horsepower sales guy on ebay, good unit. I have the chevy disk conversion for the front and the BC Broncos Caddilac Disks on the rear. New lines and flexhoses. I am running the stock Distribution block, no Porportional valve.
 
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