Brake Fluid Leak Onto Rotor?

335cabrioking · 04-28-2024, 01:22 PM

I have a 2011 e93 335i M-sport convertible, n55 engine if matters.

I was leaving to go to work in the morning about a week or two ago and noticed some brown oil looking stains all over my front passenger side rotor/disc. I thought I may have just driven through some dirty water and thought nothing of it. Within a day or two, I noticed that my brake pedal has to be pressed almost to the floor for my brakes to work. They have always been pretty loose/soft in the time that I've owned the car, but not like this. I tried to take another look at the fluid stain on the rotor but it was clean, probably from the brake pads being engaged to the rotor and wiping it off.

I have no warnings on the dash for low brake fluid, ABS, etc. It's been about a week or two since then (of careful driving) and the problem has stayed the same with no warnings on the dash or iDrive.

Could this be a busted brake line that caused that oil looking stain that I saw on my rotor that morning? Or maybe a leaking caliper? Or something else entirely like my master brake cylinder? I did hit a pothole pretty bad during the holidays last year and my suspension has been riding extremely rough since then so I could have bad shocks/struts too but I don't think those would leak all over the front of the brake rotor. And if there is a leak in the brake system causing brake fluid to leak, wouldn't there be warnings appearing on the dash?

Any advice is greatly appreciated.

ppointer · 04-28-2024, 03:12 PM

I think the symptom that bothers me the most is a brake pedal going to the floor. My opinion is that you have a leak in your braking system. Buy some brake cleaner from an auto store. Jack up the front passenger corner, take off the wheel, and spray off the caliper and brake line. Then have someone press the brake pedal while you examine for a leak. This should not be difficult to diagnose.

04-28-2024, 01:22 PM	#1
335cabrioking Registered 0 Rep 4 Posts Drives: 2011 BMW 335i Convertible Join Date: Jan 2024 Location: California, USA iTrader: (0)	Brake Fluid Leak Onto Rotor? I have a 2011 e93 335i M-sport convertible, n55 engine if matters. I was leaving to go to work in the morning about a week or two ago and noticed some brown oil looking stains all over my front passenger side rotor/disc. I thought I may have just driven through some dirty water and thought nothing of it. Within a day or two, I noticed that my brake pedal has to be pressed almost to the floor for my brakes to work. They have always been pretty loose/soft in the time that I've owned the car, but not like this. I tried to take another look at the fluid stain on the rotor but it was clean, probably from the brake pads being engaged to the rotor and wiping it off. I have no warnings on the dash for low brake fluid, ABS, etc. It's been about a week or two since then (of careful driving) and the problem has stayed the same with no warnings on the dash or iDrive. Could this be a busted brake line that caused that oil looking stain that I saw on my rotor that morning? Or maybe a leaking caliper? Or something else entirely like my master brake cylinder? I did hit a pothole pretty bad during the holidays last year and my suspension has been riding extremely rough since then so I could have bad shocks/struts too but I don't think those would leak all over the front of the brake rotor. And if there is a leak in the brake system causing brake fluid to leak, wouldn't there be warnings appearing on the dash? Any advice is greatly appreciated.
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04-28-2024, 03:12 PM	#2
ppointer Major 749 Rep 1,105 Posts Drives: '01 Z3M, '12 335is, '22 540i Join Date: Jul 2013 Location: FLL iTrader: (4) Garage List 2012 BMW 335i [5.25] 2012 BMW 335is [5.00] 2008 Infiniti QX56 [0.00] 1967 Chevrolet Corv ... [10.00] 2001 M Roadster [10.00] 2022 BMW 540i [0.75] 2009 528i [9.50]	I think the symptom that bothers me the most is a brake pedal going to the floor. My opinion is that you have a leak in your braking system. Buy some brake cleaner from an auto store. Jack up the front passenger corner, take off the wheel, and spray off the caliper and brake line. Then have someone press the brake pedal while you examine for a leak. This should not be difficult to diagnose.
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