Brake Master Cylinder Leaking... DSC On

328isawesome · 11-27-2012, 08:32 AM

When recently acquiring my current e46 the DSC light was on, it was one of those turn the car on and it turns on in a few seconds. Thought an alignment would fix it so planned on getting it done when it needed new tires. Now after I replaced all pads and rotors in the car I noticed that behind the pedal in the car there is brake fluid slowly leaking, after that in the drive way the car's brakes vibrated when slowly braking and now whenever the battery is connected some pump in the master cylinder (I believe) keeps working to the point that it drained my battery. I've read up on it and apparently the DSC system also detects when the pressure isn't right in the master cylinder so this might have been the DSC problem. Anywhoo, going to replace the master cylinder and check all relays and fuses. Any input is appreciated. Thanks!

328isawesome · 11-29-2012, 12:52 PM

Seriously, nobody has any input?

NC BMW fan · 11-29-2012, 01:25 PM

Sounds to me like a couple of things. 1) you have a leak in the master cylinder of some kind. It's troubling that you have brake fluid inside the car. That means its leaking into the brake booster, than into the car (see thread about brake booster).
2) there is no electrical connection to the master cylinder. That sounds like maybe an ABS module will not stop cycling.
Are you driving the car now? Do you have consistent firm pedal feel? The DSC light will come on if there is air in the system. leak=air.

I have a master cylinder if you are interested. $50. PM me, I'll send pics if you're interested.

11-27-2012, 08:32 AM	#1
328isawesome Registered User Join Date: Sep 2012 Location: Georgia Peaches Posts: 91 My Ride: Batmobile View My Garage	Brake Master Cylinder Leaking... DSC On When recently acquiring my current e46 the DSC light was on, it was one of those turn the car on and it turns on in a few seconds. Thought an alignment would fix it so planned on getting it done when it needed new tires. Now after I replaced all pads and rotors in the car I noticed that behind the pedal in the car there is brake fluid slowly leaking, after that in the drive way the car's brakes vibrated when slowly braking and now whenever the battery is connected some pump in the master cylinder (I believe) keeps working to the point that it drained my battery. I've read up on it and apparently the DSC system also detects when the pressure isn't right in the master cylinder so this might have been the DSC problem. Anywhoo, going to replace the master cylinder and check all relays and fuses. Any input is appreciated. Thanks!

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11-29-2012, 12:52 PM	#2
328isawesome Registered User Join Date: Sep 2012 Location: Georgia Peaches Posts: 91 My Ride: Batmobile View My Garage	Seriously, nobody has any input?

11-29-2012, 01:25 PM	#3
NC BMW fan Registered User Join Date: Jun 2012 Location: Charlotte, NC Posts: 14 My Ride: 2003 325I View My Garage	Sounds to me like a couple of things. 1) you have a leak in the master cylinder of some kind. It's troubling that you have brake fluid inside the car. That means its leaking into the brake booster, than into the car (see thread about brake booster). 2) there is no electrical connection to the master cylinder. That sounds like maybe an ABS module will not stop cycling. Are you driving the car now? Do you have consistent firm pedal feel? The DSC light will come on if there is air in the system. leak=air. I have a master cylinder if you are interested. $50. PM me, I'll send pics if you're interested.