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Old 06-09-2009, 06:06 PM
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brake pedal droppiing to the floor?

Hi I have a 1988 Toyota pickup I replaced all the rear cylinders and the calipers and brakes and rotors on the front , replacet master cylinder emergency cables about 8 months ago,I was driving to work stepped on the brake and it went too the floor, the emergcey brake became loose also.
it seems like it needs adjustment maybe it has something to do with it I don't know.The cylinders aren't leaking no fluid on any of the tires, maybe i need to bleed the lines? but why did the pedal just go down , new master cylinder is bad? booster is bad?

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Old 06-09-2009, 07:16 PM
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if your brakes WERE fine for over 8 months....
I'd be guessing that you HAVE A PROBLEM........
is there fluid in m/c???
is it still full???
you say calipers are still dry,,,sounds more like a crack in a brakeline...
assuming that the m/c is still in good shape...
check fluid levels first,,then starting with Right Rear..bleed lines...R/R -L/R-R-F-L/F...
note...when bleeding brakes ..especially if alone,, I use a piece of clear fish tank hose around a foot long,,and make a loop facing upwards..
this does 2 things.. 1 -you can see the air bubbles travel thru line and 2- no air returns into brakes..
you should only have to pump brakes 1-2 times and then gravity feed..you should see it flow,, and there should even be a color change as you go from old to new fluid...
........hope this helps.........
........oh yeah and chech the fluid level often..
........don't want to have to start all over again.........
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Old 06-09-2009, 08:07 PM
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I suppose you verified there is fluid in the master cylinder?

Did you verify the master cylinder linkage is still connected to brake pedal?
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Old 06-10-2009, 08:16 PM
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there is fluid in the master cylinder reservoir
I see no fluid leaks nothing on the ground or tires have to get into it ,when I get some time ,I am working on my 1930 coupe new heads,cam it isn't running perfect yet I started it up and the rear seal is leaking and need to set lifters again will let you know what I find when I get around to the truck. the emergency brake on the truck became loose also all at the same time I don't think it could be related?
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Old 07-14-2009, 07:09 AM
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I have a friend of mine with the same problem in his 41 Chev. It has disc/disc, pinto master/booster. He claimed once in a while he starts the car and backs up or gets to the end of the drive way his pedal goes all the way to the carpet and after one or two pumps the pedal is back and firm. It never happens at road or highway speeds. Only low RPM and right after he starts the car. So I checked the M/C and found the fluid black in color. I took the m/c apart and the seals were good, no tears or even scratches on the lips. Cleaned it up, bench bled, checked the rod to piston clearance while it was out and installed it back. Completely bled the entire system starting from the longest to shortest line approx three times (by refilling the m/c when 1/2 empty) per corner ensuring clean and clear fluid. Did the check on the booster and went for a ride. Also no pedal creep for a minute hold. Great, good solid pedal and panic stops. After shooting the breeze for a few minutes he got in the car, started it to go home, backed up, BOOM, no pedal. ***, pump the pedal and all is well. SO, who can shed some lite on this?

Last edited by fierosum; 07-14-2009 at 07:15 AM.
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Old 07-14-2009, 05:48 PM
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my truck had a bad rear wheel cylinder.
It sounds like you have a bad master clyinder, did you check your brake lines?
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Old 07-14-2009, 06:20 PM
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If you lost the e-brake at the same time, something probably came apart in the rear wheels.
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Old 07-14-2009, 07:52 PM
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watchdude1 - thanks for the response, all brake lines and calipers are new (discs at all four wheels), flow well and bleed well. Someone suggested that one minute of pressing the pedal is not long enough to check the m/c. I replied that the major brake component manufacturers suggest one minute not 5 like I was told. Any experience on this? I always used 60 -90 secs. Thx.
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Old 07-14-2009, 08:10 PM
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Quote:
Originally Posted by fierosum
watchdude1 - thanks for the response, all brake lines and calipers are new (discs at all four wheels), flow well and bleed well. Someone suggested that one minute of pressing the pedal is not long enough to check the m/c. I replied that the major brake component manufacturers suggest one minute not 5 like I was told. Any experience on this? I always used 60 -90 secs. Thx.

Do do what? Are you talking about bleeding? That long is an overkill.

Tell me, is it still happening or was it a one time thing? Does it just to straight down when you step on it, or after you are holding it, it just "slips" down?

Brian
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Old 07-15-2009, 06:57 AM
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I thought I explained the situation clear, maybe not. He backs up or drives up the driveway to cruise and the first push of the pedal it goes to the floor. Pump it once and pressure is back and stays firm all day. This happens approximately once every 20 starts. Never while on the road. The minute test is when checking the m/c by applying pressure to the pedal and holding it for 60-90 seconds to check if it creeps down. It does not. To avoid repeating, just reread my previous post "I have a friend of mine............". I hope I was clear this time.
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Old 07-15-2009, 08:17 AM
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I'd be guessing the issue is you're using a disc/drum MC with a disc/disc setup. Put a residual valve inline with the rear and it should stop the rear pistons retracting completely which I am betting is why he has no pedal when he first starts.
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Old 07-15-2009, 09:42 PM
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Quote:
Originally Posted by fierosum
I thought I explained the situation clear, maybe not. He backs up or drives up the driveway to cruise and the first push of the pedal it goes to the floor. Pump it once and pressure is back and stays firm all day. This happens approximately once every 20 starts. Never while on the road. The minute test is when checking the m/c by applying pressure to the pedal and holding it for 60-90 seconds to check if it creeps down. It does not. To avoid repeating, just reread my previous post "I have a friend of mine............". I hope I was clear this time.
Sorry I bothered you.

Brian
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Old 07-15-2009, 10:19 PM
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Quote:
Originally Posted by watchdude1
Hi I have a 1988 Toyota pickup I replaced all the rear cylinders and the calipers and brakes and rotors on the front , replaced master cylinder emergency cables about 8 months ago,I was driving to work stepped on the brake and it went too the floor, the emergency brake became loose also.
it seems like it needs adjustment maybe it has something to do with it I don't know.The cylinders aren't leaking no fluid on any of the tires, maybe i need to bleed the lines? but why did the pedal just go down , new master cylinder is bad? booster is bad?

Toyotas have a rear proportioning valve and air gets trapped in it. Some even have bleeder screws in them. Hope this helps.

Kurt
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Old 07-15-2009, 10:27 PM
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who's brakes are we trying to fix?
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Old 07-16-2009, 03:44 PM
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Let us know what you find. I posted the bleeder in the rear proportioning valve info because I also had a problem with one and found it the hard way. It does not explain why it would work ok for 8 months. I have seen loose front wheel bearings cause the brake pedal to drop also. But it has to be real loose.

Last edited by RODDER18; 07-16-2009 at 06:14 PM.
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