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Brake pedal goes to floor
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Nick
Anonymous Poster
DirtyNicker@hotmail.com
Nov 19, 2008, 3:29 PM
Post #1 of 12
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Brake pedal goes to floor
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I have been working on my grandmother's 1994 Buick LeSabre for almost a month now. Each time I fix it, something else goes wrong. First I replaced a rusted and leaking brake line going to the right rear wheel cylinder. After a short while, the brake pedal got mushy so I replaced the master cylinder because I couldn't find anymore air in the system. Before I could even get the car out of the garage, the brake line blew out at the rear mounted proportioning valves. I have since replaced all the lines and proportioning valves in the rear of the vehicle. I bled all of the air out of the system and the pedal feels great (stiff), that is until I start the vehicle which is when the pedal goes to the floor. Please help. My grandpa is in a rehabilitation center and my grandma needs to sell the car for extra cash.
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Nick
Anonymous Poster
DirtyNicker@hotmail.com
Nov 19, 2008, 3:40 PM
Post #2 of 12
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Re: Brake pedal goes to floor
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Oh, I forgot to mention that the master cylinder was bled before hooking up the lines. My cousin helped me do it since he had done the same on a car just like this one less than a month ago.
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Loren Champlain Sr
Veteran
/ Moderator
Nov 19, 2008, 4:07 PM
Post #3 of 12
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Re: Brake pedal goes to floor
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Air in the hydraulic system will give you a 'mushy' feeling pedal. If you pump the pedal a time or two, does it get better? I don't like using someone's foot to bleed brakes. It is too easy to damage a master cylinder, that way. But...After bench bleeding, there still may be some air trapped between the master and the lines. All it takes is one itty-bitty bubble to ruin your whole day. Assuming that all of the air has been bled, then I would suspect one of two things...the rear brakes are terribly out of adjustment or a defective master cylinder. Again, assuming, you have no more hydraulic leaks.
Loren
SW Washington
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Nick
Anonymous Poster
Nov 19, 2008, 7:36 PM
Post #4 of 12
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Re: Brake pedal goes to floor
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I loosened all the bleeder screws two nights ago and let the fluid run out while topping off the master cylinder so it never went empty. This is called gravity bleeding. I did this just to be sure all of the air was out. Note that I only have the mushy pedal when the engine is running, before that the pedal is solid.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 19, 2008, 8:28 PM
Post #5 of 12
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Re: Brake pedal goes to floor
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Gravity bleeding alone may not be sufficient. The firm pedal when engine is off isn't all that surprising without power booster working so that's unconclusive by itself.
Does this have abs? There could be a different bleed procedure for this. Look if so if there are more bleeders along route.
Not sure just what Loren meant by "someone else's foot" but if you don't have a power bleeder you should have a helper push on pedal and release fluid at bleeders - longest line first, shut bleeder before that foot has realeased pressure on pedal and repeat till no bubbles are seen and continue on thru each brake. If bench bleeding didn't work out well this can be THE problem and may need to be redone.
IMO - gravity alone cal allow a bubble to set at a high spot in lines, force should move it along to bleed out. Double check your connections where you replaced line again also,
T
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Nick
Anonymous Poster
Nov 20, 2008, 2:47 PM
Post #6 of 12
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Re: Brake pedal goes to floor
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Thanks for the suggestions. It is an abs system, so I will check to see if there is a special step that I am missing. As far as the regular bleeding goes, I'm almost certain there is no air in the lines. I've bled brakes many times in my life and this is the first time I've had a major (and I mean MAJOR) difference when the vehicle is started. If anyone has any off the wall suggestions I would like to hear them. This is very abnormal for me to even have a problem with a brake pedal when I'm done with the work. Maybe I should buy a dealer manual or maybe I recieved a bad reman master cylinder, which is my uncle's first thought.
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way2old
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/ Moderator
Nov 20, 2008, 4:15 PM
Post #7 of 12
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Re: Brake pedal goes to floor
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Just for no other reason than that I am curious, does the master cylinder sit at a fairly steep angle? If it does, jack up rear of vehicle till master is level and try one more time.
Being way2old is why I need help from younger minds
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Loren Champlain Sr
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/ Moderator
Nov 20, 2008, 5:07 PM
Post #8 of 12
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Re: Brake pedal goes to floor
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Your problem really doesn't sound like air. A low pedal is almost always an adjustment or a master cylinder problem. Rebuilt master cylinder? I wouldn't put a rebuilt unit on my wheel barrow. I've seen too many master cylinders ruptured by having someone push on the brake pedal and allowing it to go all the way to the floor when bleeding. Of course, this shouldn't happen with a new unit. But....
Again; Does the pedal height increase by pumping the pedal? If it does, check your rear brake adjustment. If it has rear disc brakes, apply the e-brake to it's limit, the try again. If none of this helps, I'd suspect the master.
Loren
SW Washington
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Nick
Anonymous Poster
Nov 28, 2008, 8:30 PM
Post #9 of 12
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Re: Brake pedal goes to floor
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Thanks. I will install a different master cylinder this weekend and make sure the master cylinder is level also since it is mounted at an angle.
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Nick
Anonymous Poster
Dec 15, 2008, 8:17 PM
Post #10 of 12
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Re: Brake pedal goes to floor
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Ok, my update. I have installed a new master cylinder, bench bled (on vehicle since there is a hose that runs from the master cylinder resevoir to the ABS pressure modulator assembly) then I have continuously bled the complete braking system with a pressure bleeder (no pedal pumping this time). The pedal is stiff until the engine is started then it goes to the floor. The brakes work, but I think only the rear. At this point I have contacted somebody about special procedures for purging air from the ABS pressure modulator assembly and hope to hear back from them soon. If anyone has anymore ideas, please help me.
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dude33333
New User
Apr 12, 2010, 4:40 PM
Post #11 of 12
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Re: Brake pedal goes to floor
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Nick, I hope you solved this problem. I am having the same exact issue. Did bleeding the air from the ABS pressure modulator assembly fix it? please respond!! thanks!!
Eric
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 13, 2010, 12:04 AM
Post #12 of 12
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Re: Brake pedal goes to floor
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Eric - that thread is older than dirt. Starting your own with your own specifics would help you better,
T
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