brake pedal goes to floor with engine on

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brake pedal goes to floor with engine on

Postby Smokey5159 on Mon Nov 20, 2017 11:36 am

Hi guys,
Just wonder if anyone has experienced and would know why my 2011 MN Triton's brake pedal goes to the floor with the engine running, but is as hard as a rock with the engine off. The fluid has been replaced 8 months ago, and all front and rear pads and shoes renewed - system bled, and the brakes seem to be working ok whilst driving. Just seems to be an unusual occurrence and I have noticed this question asked by many other vehicle forums - perhaps it's more common than we think. I've just not seen a conclusive answer that adequately explains this.
Cheers,
Paul
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Re: brake pedal goes to floor with engine on

Postby WUNSIE on Mon Nov 20, 2017 4:48 pm

The pedal is hard without the engine running as the brake booster is offering no assistance, to me its like the seals on the piston in the master cyl are shot
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Re: brake pedal goes to floor with engine on

Postby Smokey5159 on Tue Nov 21, 2017 9:50 am

Thanks for replying...
Just wondering - would the pedal not still go to the floor with the engine off if the seals are worn..?
Some folks say that it's to do with the ABS proportioning system, and that it is quite common. They also say that
even after replacing the MC, they still have the same experience...
Just curious..!
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Re: brake pedal goes to floor with engine on

Postby bolt on Wed Feb 28, 2018 12:22 am

I just changed the front and rear brakes and now the pedal goes to the floor.
I understand it could be the master cylinder leaking
or air has gotten into the system
or dirty fluid might have gotten into the abs system

does anyone know how to test the Master Cylinder?
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Re: brake pedal goes to floor with engine on

Postby NowForThe5th on Wed Feb 28, 2018 2:21 am

Most likely air in the system. The fluid is probably due to be replaced anyway, so drain, refill, flush, refill, bleed and test.

More detailed information in the online manual.
Chris

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Re: brake pedal goes to floor with engine on

Postby bolt on Wed Feb 28, 2018 7:01 am

Thanks Chris will try and change the fluid and bleed will post what happens.
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Re: brake pedal goes to floor with engine on

Postby bolt on Wed Feb 28, 2018 12:17 pm

ok I just took the tirton for a half hour drive before i bleed the fluid to see if the pedal would come back.
if I pump rapidly 3 times the brakes work so so but feel like something grinding / pulsating.
if i depress slowly the pedal goes to floor with no stopping power.

also my hand brake is not holding the vehicle like it used to.

going to bleed the brakes now. :|
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Re: brake pedal goes to floor with engine on

Postby bolt on Wed Feb 28, 2018 3:55 pm

bled the brakes. seems to have fixed the problem although the passenger side rear did not matter how long i was pumping there where tiny air bubbles coming out of what looked like the bleed nipple even though I had nipped it up so I am a bit confused.
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Re: brake pedal goes to floor with engine on

Postby RHKTriton on Wed Feb 28, 2018 5:38 pm

It would only take a bit of grit to stop the nipple sealing properly.

Did you use the tried and tested method of pushing the fluid out with the brake pedal or are you sucking on the nipple? :)

I usually adjust the rear brakes and then perform the bleeding sequence, when required. Gives nice braking performance with load spread properly across front and rear brakes.
Don't let the b'strds get you down!!
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Re: brake pedal goes to floor with engine on

Postby NowForThe5th on Wed Feb 28, 2018 8:13 pm

bolt wrote: I just took the tirton for a half hour drive before i bleed the fluid to see if the pedal would come back.


You have a death wish?

As RHK mentions, there is a specific bleeding sequence which should eliminate all air in the system. He's also right in saying that it doesn't take much to stop the nipple sealing properly. Remove it and clean then flush and clean where it screws in.
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Re: brake pedal goes to floor with engine on

Postby bolt on Wed Feb 28, 2018 8:48 pm

No Death Wish here.

yes I used the tried and tested method of pushing brake pedal but I used 2 people on to push pedal and myself to turn the nipple.

as the brakes are working fine now and I took the wheels off again to have a look to see if there were any leaks from pistons or hoses (there is no leeks) perhaps the bubbles where just coming up the tube as the fluid drained out of tube into container (yes the end of the hose was submerged in fluid.)

when the bubbles appeared was after closing the nipple and letting pedal up. which if the nipple was not sealing properly should it not have been sucking not blowing bubbles?
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Re: brake pedal goes to floor with engine on

Postby MilkmanDan on Wed Apr 05, 2023 2:27 pm

Hi all. My master cylinder is shot, having problems finding replacement for an ABS & ASC vehicle. Are these just not available or a parts interpreter miscommunication? Anyone got a supplier they can recommend?
Cheers
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Re: brake pedal goes to floor with engine on

Postby NowForThe5th on Wed Apr 05, 2023 4:26 pm

Amayama or Partsouq?
Chris

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Re: brake pedal goes to floor with engine on

Postby MilkmanDan on Thu Apr 06, 2023 5:12 pm

NowForThe5th wrote:Amayama or Partsouq?


Thanks mate.

So Ive had to get a genuine one, from my several phone calls an ABS & ASC equipped vehicle has a specific master cylinder (for whatever reason I’m unsure), aftermarket is either ABS (non ASC) or no ABS. So luckily my partner works for VACC and am paying $610 for one and not $840 retail, but a bit of a kick in the nuts that for whatever reasons arent supported.
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