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Discussion Starter #1
Ok, first off I have the original disc brakes in the front and the disc kit in the back from a 99 explorer. The discs in the front need to be replaced when I get some money, I don't know if that might have anything to do with the problems i'm having. For a while my brakes have been hissing vacuum when they are depressed, and i was told to replace the booster, so I did so. Now, when i push the brake pedal it goes to the floor and sticks there. I bled the brakes and found a whole bunch of air in the rear driver line. This firmed up the pedal very nicely but it still stuck down for a bit before coming back. After a day of driving like this the pedal went back to the floor. I took it in to my mechanic who replaced the master cylinder and made new lines going into the master cylinder. This firmed up the pedal again but after another day of driving i have no brakes again and the pedal doesn't like to return when being depressed. Any ideas?

Thanks,
Brett
 

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Where did you get the replacement Power Booster ??? I'm assuming that when it "hissed" the pedal was at least coming back up , right ??? Now you replaced the power booster and the pedal is not behaving correctly..

I'd be suspect of the replacement booster
 

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Sounds like the new booster may be the problem. It uses vacuum to assist in brake pedal pressure. Could be that the internal valve is not sealing allowingyour vacuum to pull the pedal back up. Also, if your pedal is going all the way to the firewall, that could cause your booster to lag in the pedal return. I would check the rest of the system for leaks/air first. If you have the two piece rear line, it can have a leak at the union. I've also seen crushed lines from people jacking the car up at the wrong point. This could make bleeding nearly impossible. Just some thoughts...
 

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Discussion Starter #6
I got the booster from Kragen's, and the pedal did return before I switched it out. The thing that puzzles me is the air in the lines that keeps coming back, would the defective booster be responsible for that too?
 

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the air in the lines that keeps coming back
Did your mechanic bench bleed the new MC before he/she put it in? Did they bleed the system lines from passenger rear, around to driver front? I would think that if the line was leaking and sucking back in air, you'd see fluid leaking. The booster doesnt put air into the line.
Just a couple of thoughts.
 

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Kragen is not possessive, ARRGH!!!!!
 

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Discussion Starter #9
Kragen is not possessive, ARRGH!!!!!
Hahaha the best part about that quote is that I work there, isn't that sad... anyways, thanks to everyone for the help, yes my mechanic bench bled the cylinder and bled the lines right, it ended up being a few problems. The master cylinder ended up being bad, and the check valve next to it was leaking fluid. Now the pedal feels ok, and it still sticks a bit but I am reluctant to replace the booster because it has to be special ordered and i can't afford to have my car down just yet, so hopefully i'll get it changed soon.

Thanks,
Brett
 
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