brake pedal droppiing to the floor?

2181 Views 16 Replies 9 Participants Last post by watchdude1, Jul 20, 2009

watchdude1

Discussion Starter · Jun 10, 2009

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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bobjob

· #2 · Jun 10, 2009

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......... :sweat:
........oh yeah and chech the fluid level often..
........don't want to have to start all over again.........

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001mustang

· #3 · Jun 10, 2009

I suppose you verified there is fluid in the master cylinder?

Did you verify the master cylinder linkage is still connected to brake pedal?

watchdude1

Discussion Starter · #4 · Jun 11, 2009

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?

fierosum

· #5 · Jul 14, 2009 (Edited)

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?

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watchdude1

Discussion Starter · #6 · Jul 14, 2009

my truck had a bad rear wheel cylinder.
It sounds like you have a bad master clyinder, did you check your brake lines?

T-bucket23

· #7 · Jul 15, 2009

If you lost the e-brake at the same time, something probably came apart in the rear wheels.

fierosum

· #8 · Jul 15, 2009

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.

MARTINSR

· #9 · Jul 15, 2009

fierosum said:
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

fierosum

· #10 · Jul 15, 2009

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.

robin58

· #11 · Jul 15, 2009

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.

MARTINSR

· #12 · Jul 16, 2009

fierosum said:
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

RODDER18

· #13 · Jul 16, 2009

watchdude1 said:
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

speede5

· #14 · Jul 16, 2009

who's brakes are we trying to fix?

RODDER18

· #15 · Jul 16, 2009 (Edited)

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.

fierosum

· #16 · Jul 17, 2009

Appology

martinsr - my apology to you and others that I may have offended. I was critical to myself not to any response. Sometimes one thinks the explanation was adequate, obviously it was not. So the bad is on me. Yes the original post was by "watchdude1", but again I thought that when someone does a future search on "low pedal" they would read different solutions within one post. Again I am wrong and apologize to watchdude1 for hijacking his thread. Carry on.

watchdude1

Discussion Starter · #17 · Jul 20, 2009

fierosum said:
martinsr - my apology to you and others that I may have offended. I was critical to myself not to any response. Sometimes one thinks the explanation was adequate, obviously it was not. So the bad is on me. Yes the original post was by "watchdude1", but again I thought that when someone does a future search on "low pedal" they would read different solutions within one post. Again I am wrong and apologize to watchdude1 for hijacking his thread. Carry on.

NO problem I did the same thing

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