[DervJim]

Hey guys

My E91 recently has started with some odd brake behaviour, whereby the pedal will sink at certain times but not others. No fluid loss at all and healthy level in the header for it.

So when I start my car in the morning the pedal feels ok but at the end of my street when I stop at junction the pedal will sink really low. The brakes still function perfectly well in respect of stopping the car, but there's tons of fere pedal movement before that.

If I pump the pedal a couple of times then it firms up just fine and feels normal.
Any time I stop the engine (like stopping for filling up fuel etc), then it's like it resets then to having sinking pedal again until I pump it a couple times again then it mostly stays good.

Occasionally while driving it sinks when I get to a junction, but again, pumping it a couple times again makes it then behave fine again.

I'm going to flush/bleed the system and try doing whatever ABS diagnostic I can do in INPA or with a delphi, but it's just kinda inconsistent behaviour of the pedal sinking which is a bit weird to me.
I've tested it loads of times on quiet roads that when it's doing the sinking pedal thing that it will still stop perfectly well if i need it to, and ABS will kick in if I make it, or can lock it up etc, but it just feels nasty how it is so I want to get it dealt with promptly.

Thanks!

[mweisdorfer]

Originally Posted by DervJim

Hey guys

My E91 recently has started with some odd brake behaviour, whereby the pedal will sink at certain times but not others. No fluid loss at all and healthy level in the header for it.

So when I start my car in the morning the pedal feels ok but at the end of my street when I stop at junction the pedal will sink really low. The brakes still function perfectly well in respect of stopping the car, but there's tons of fere pedal movement before that.

If I pump the pedal a couple of times then it firms up just fine and feels normal.
Any time I stop the engine (like stopping for filling up fuel etc), then it's like it resets then to having sinking pedal again until I pump it a couple times again then it mostly stays good.

Occasionally while driving it sinks when I get to a junction, but again, pumping it a couple times again makes it then behave fine again.

I'm going to flush/bleed the system and try doing whatever ABS diagnostic I can do in INPA or with a delphi, but it's just kinda inconsistent behaviour of the pedal sinking which is a bit weird to me.
I've tested it loads of times on quiet roads that when it's doing the sinking pedal thing that it will still stop perfectly well if i need it to, and ABS will kick in if I make it, or can lock it up etc, but it just feels nasty how it is so I want to get it dealt with promptly.

Thanks!

Use ISTA D to bleed the ABS system & report back

[335i54n]

yeah if youre not leaking externally, then its internal and hopefully the master and not the abs

[DervJim]

Thanks

I'll try bleeding it first (think I already have different versions of Ista D on a laptop I use for various diagnostic stuff) and will see how it is after.

I was amazed at how cheap a used Master is actually so am assuming I can probably get brand new ones for a reasonable price on that basis, but not actually looked yet.

[eljay]

Yes, perform bleed per ISTA to ensure ABS system is bled too.