Member
I've bled the brakes on my 2000 540i twice with no improvement. The brakes stop the car fine, but the pedal isn't firm, and it slowly sinks with constant firm pressure. A forum search points to one possibility, failing master cylinder.
The problem is that I see no leaks, and haven't had to add brake fluid.
Any other actions I should take before replacing?
When in doubt--gas it!
Artifically Aspirated
Moderator
Have you checked up under the dash for a leak where the brake rod goes into the master cyl?
Member
Sinking pedal is a failing master cylinder. I had the same issue in my Acura a few years ago. No leaks or anything the pedal just slowly sunk to the floor.
Member
No, will do.
When in doubt--gas it!
Member
Internal leakage can cause the soft sinking pedal.
Ed in San Jose '97 540i 6 speed aspensilber over aubergine leather. Build date 3/97. Golden Gate Chapter BMW CCA Nr 62319.
Member
Classic example of a bad master cyl, just as posted above.
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Member
Ok, I have replaced the master cylinder. There was evidence of leaking below the mounting point on the vacuum booster.
But...though it's a more firm pedal, it's still sinking. I've pressure-bled it three times with no change. Could air be lurking in the ABS system? I don't have a warning light.
All the calipers are dry.
When in doubt--gas it!
Member
I experience same issue on my 530i. dealer told me master cylinder or brake booster needed to be replaced and that its normal feel for age of car....
this is after having front pads and rotors replaced with new OEM.
other option is stainless steel lines don't know if that would help or a better brake pad.
Member
Years ago on my 2003 540 I had a similar problem.
Turned out I needed to use software to open the ABS during bleeding to get old fluid/air out of the ABS.
Nice firm pedal feel afterwards.
Can't recall for sure, but I THINK it was INPA software that was used.
<== Steptronic Sealbeach740
2000 740i sport: 74k Green/Tan chrome MPars, clear corners, quad brake lights, AIC hi-beams, Hoen fogs, 16x9 screen, MKIV, TFT LCD screen in back, license plate backup camera with "on demand" switch, iPod audio/video (CDC/iPod audio switching, iPod video on 16x9 screen), Basslink, gauge rings, ///M pedals, switched steptronic +/- shifting mode, E46 paddle shifter steering wheel, Dinan engine & tranny software upgrade, DDEs controlled via Euro fog light switch, painted calipers with "BMW" lettering, windows up/sunroof close via remote.
2003 540i sport: 81k, Sterling grey/grey, MKIV Nav, PDC & CWP - Added license plate backup camera with "on demand" switch, paddle shift steering wheel, windows up/sunroof close via remote, Akebono's, painted calipers with "BMW" lettering, quad brake lights, iPod audio via AUX mode/video via 16x9 screen, BMW TV tuner, ///M pedals & gauge rings.
Member
Seeing as how the OP's car is a MY00 it would have DSC and ABS so I could see fluid/air getting trapped.Originally Posted by sealbeach740
Fred, I see you are in Wyoming. Not sure what kind of options you have for software/shops with software. I believe the Foxwell NT510 Scanner with BMW Software will do the same functions of INPA. If you would like me to check on a friend's MY03 540 before you buy the scanner, just let me know.
Wade
Member
This place is full of good people.
Member
I would really appreciate that, Aubergine! You are correct in assessing my limited options here. BMW sources are in N. Colorado, about 250 miles away.
Scubajim20: you are absolutely right!
When in doubt--gas it!
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