brake pedal going to floor when running???

[suprra_girl]

When the car is off the pedal is awesome, right up and no air.
As soon as it start the car the pedal goes to the floor.

Anyone had this? How do i fix, i really wanna drive my car today
but with brakes haha

 

[AJ'S 88NA]

When the car is off the pedal is awesome, right up and no air.
As soon as it start the car the pedal goes to the floor.

Anyone had this? How do i fix, i really wanna drive my car today
but with brakes haha

Never had that problem, but it sounds like a problem with the brake booster. Check your vac lines to it.

If you let the reservoir get real low you may have air in your booster. It will have to be bled.http://cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=BR&P=6

 

[Mr.PFloyd]

how long has the brake booster not had any fluid in it?

 

[suprra_girl]

quite some time

i bled the master, then abs, then wheels when off i have awesome pedal
i start it, and then the pedal loses all pressure and just floats off down to the floor

 

[OfnaRcR4]

Never had that problem, but it sounds like a problem with the brake booster. Check your vac lines to it.

If you let the reservoir get real low you may have air in your booster. It will have to be bled.http://cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=BR&P=6

Master cylinder?

Booster should have air in it at all times. It is normal when you pump the brakes with the car off to have a hard peal. When you start the car the pedal should go down. That is the booster doing its job. It's just not supposed to go all the way down.:biglaugh:
The reason you get a hard pedal when the car is off is because you are depleting the booster.
Sounds like you have air in the system/not enough fluid. I would keep bleeding it.

 

[CyFi6]

i vote master cylinder/air. When you press the pedal and it slowly sinks to the floor it indicates fluid leaking past the piston in the master cylinder, assuming you have no external leaks

 

[OfnaRcR4]

If it sinks without your foot on it i would say master cylider.

 

[Lunch boxsj]

yeah i had that happen to me, i had to get a new master cylinder

 

[suprra_girl]

i bled those lines ALOT and it's all straight fluid, no air at all.
When i pulled off the vacuum line to the booster there was a huge pshhhhhhhh so that suggests it's holding vacuum.
When the car is off i push on the pedal and hold it and the pedal doesn't go down so that suggests no leaks either
There's also no fluid pouring down my booster
And no it doesn't sink without my foot on it, it's just very very soft/easy to push down

Please please please help
I wanna drive my car

 

[lilazni3uoy]

you need to make sure you have that valve, that goes from the brake booster, to the intake manifold, !! or else the pedal will go to the floor even tho it's bled

 

[twinturbozs]

Sounds like you have an internal leak in the MC. I would check for leaks around your calipers first. My guess is to replace the MC since its relatively cheap.

 

[suprra_girl]

thanks for the suggestion but i already replaced the master cylinder and i had absolutely no change whatsoever.
I do find it suspicious that i have funny fluidy squishy sounds in my booster tho

 

[suprra_girl]

you need to make sure you have that valve, that goes from the brake booster, to the intake manifold, !! or else the pedal will go to the floor even tho it's bled

well i know my lungs don't near count towards engine vacuum lol but i can blow through the valve but not suck through it so i guess it's not leaking

if the booster doesn't fix it i will replace that next anyhow
thanks

 

[suprra_girl]

i just blew 10psi into the valve and it didn't leak held pressure fine so i guess it's not the valve

 

[cuel]

thanks for the suggestion but i already replaced the master cylinder and i had absolutely no change whatsoever.
I do find it suspicious that i have funny fluidy squishy sounds in my booster tho

Sounds like the old master cylinder was leaking into the vacuum booster. You might be able to find a used one in the f/s section.

 

[suprra_girl]

hmmm you've never seen our driveway pics have ya
we're quite well known in the mk3 world here in nz and the local parts supplier lol, i changed the booster, bled again and now i have brakes wooohooo hehe

btw love your avatar lol

 

[GrimJack]

Booster would have been my choice as well. My old room mate blew the booster in his DSM, it would suck brake fluid through it into his intake manifold. Car was running really funny while trying to burn brake fluid along with gasoline.