General Sinking brakes

[dejan91]

Hi all

For couple of weeks i am working on my Stilo's sinking brake pedal. When the engine is off the brake pedal is firm as it should be but when you start the engine and press the brake pedal it starts slowly sinking to the floor. I replaced the master cylinder, i bench bleeded the MC the i bleeded the whole system on the car and also bleeded the abs unit via MultiEcuScan. There is definitely no leaks and none of the calipers are stuck. It is possible that the ABS unit is making this problem ??

 

[Ralf S.]

Hi all

For couple of weeks i am working on my Stilo's sinking brake pedal. When the engine is off the brake pedal is firm as it should be but when you start the engine and press the brake pedal it starts slowly sinking to the floor. I replaced the master cylinder, i bench bleeded the MC the i bleeded the whole system on the car and also bleeded the abs unit via MultiEcuScan. There is definitely no leaks and none of the calipers are stuck. It is possible that the ABS unit is making this problem ??

If the pedal is hard when the engine is off but spongey when the engine is running then there is still air in the system.

I agree it's probably inside the ABS unit but I don't think there is a fault with the ABS unit; they're just difficult to bleed.

I would only worry about the front brakes for now. The rear brakes don't get much braking force to they're not going to make much difference to the pedal.

I don't know about using the MES software to control the ABS system so I can't help you with that - I've only ever bleed the brakes, driven the car around, bled the brakes some more.. left it a week until there was a full moon, bled the brakes some more... just getting fluid through the system eventually made my brakes "not bad".. although still not great.

Also, use a pressure bleeding system (although the caps never fit the Fiat master cylinder very well) so it saves the seals in the master cylinder from twisting.

If you bleed it using the pedal, use a series of short prods (a few cm only) and release the pedal each time, not a long press of the pedal all the way to the floor.


Ralf S.

 

[dejan91]

if the pedal is hard when the engine is off but spongey when the engine is running then there is still air in the system.

I agree it's probably inside the abs unit but i don't think there is a fault with the abs unit; they're just difficult to bleed.

I would only worry about the front brakes for now. The rear brakes don't get much braking force to they're not going to make much difference to the pedal.

I don't know about using the mes software to control the abs system so i can't help you with that - i've only ever bleed the brakes, driven the car around, bled the brakes some more.. Left it a week until there was a full moon, bled the brakes some more... Just getting fluid through the system eventually made my brakes "not bad".. Although still not great.

Also, use a pressure bleeding system (although the caps never fit the fiat master cylinder very well) so it saves the seals in the master cylinder from twisting.

If you bleed it using the pedal, use a series of short prods (a few cm only) and release the pedal each time, not a long press of the pedal all the way to the floor.


Ralf s.

Yesterday i had some time to try some more bleeding and than just of curiosity i clamp down rubber hose on left front caliper (as you said focus on the front brakes) and the pedal became much better. When i will have more time i will investigate more and report what was the problem...

Tnx for the tip