Power Brake Booster
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New User
Joined: Mar 2004
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Power Brake Booster
have a problem with my 79 Bronco power brakes. The problem is there is none. I replaced the master cylinder and bled the brakes likes. Still no brakes. Pedel is better but pedel will still goes to the floor hard. I was told it could be the power brake booster. Does any one agree with this or is there something else I should look at?
Postmaster
Joined: Feb 2003
Posts: 3,439
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From: Spokane WA
there is a problem somewhere other then the booster. A bad booster should make a pedal harder
master cylinder bench bleed?
correct master cylinder?
lines and hoses good?
got fluid at all 4 wheels when bleeding?
rear shoes adjusted right?
master cylinder bench bleed?
correct master cylinder?
lines and hoses good?
got fluid at all 4 wheels when bleeding?
rear shoes adjusted right?
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New User
Joined: Mar 2004
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additional info
I was able bled all the air out of the line and got fluid to all brakes. The petel feels hard all the way down but the brakes are slow to stop. Also when I apply the brakes at idle the engine rpm rise to a couple of seconds.
Tim
Tim
Posting Guru
Joined: Jul 2003
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From: Independence, MO
the rpms fluctuating when you mash the peddle in a indacator of a bad power booster being that it is vaccum operated, but that dosnt mean you dont have other problems just because you have fluid at each whel dosent mean there isnt air trapped somewhere, bleed them again starting with right rear, left rear, right front, then the left front. did you bleed the master cylinder before connecting the lines ? DW
Elder User
Joined: Apr 2002
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From: NJ
do you have 4 wheel drum brakes on that 79? did you bleed the master on the bench first? are you 100%sure yuo got the correct master.if all these are correct then i would suspect the actuating valve on the booster. if your booster diaphram was bad your truck would not run correctly because there would be a vacumn leak.
Lead Driver
Joined: Jul 2003
Posts: 7,404
Likes: 52
From: Wheatland, Mo
Did someone mention the booster? 
The booster going bad can cause all sorts of issues and act differently. WHen Mine went out, it was applying the brakes by themselves. It would pull so hard that I had to put my foot under the pedal and pull like hell to get the truck to move. Good thing is that the booster only cost about $20. and took all of 30 minutes to replace.
The booster going bad can cause all sorts of issues and act differently. WHen Mine went out, it was applying the brakes by themselves. It would pull so hard that I had to put my foot under the pedal and pull like hell to get the truck to move. Good thing is that the booster only cost about $20. and took all of 30 minutes to replace.
