xoxbribri

2009 C-300 Luxury 4Matic w/ 72k on the odometer.

Thursday my check brake fluid level low light came on in the center of my dashboard. I stopped at my dad's mechanic (only works on foreign cars). He filled up the reservoir and said it can be one of three things. 1) My brakes need to be replaced (they don't) or 2) there is a leak somewhere or 3) there is a sensor that is bad that is triggering it. Anyway, yesterday I was driving and the same light came on again. So again, I stopped (somewhere else this time) to fill up the reservoir just to get home (I was maybe 20 minutes from home) and by the time I pulled into the parking garage of my apartment building, the light came back on. Now, when I hit the brakes, my car stops almost instantly, like I don't feel that there is a leak but then again I'm not a mechanic.

So 2 questions, could it be a sensor issue? & anyone who has experienced this, how much would this cost me approximately?


Thanks!

OLI77

Sensor issue sounds right. It is not likely a leak. That is last place you want a leak.

When you say you add more brake fluid, how much are you adding each time? Is the level low before you add any? Cause that does sound like a leak. When the light turns on, is the level in the level low?

Alfadude

If you had to fill up the brake fluid reservoir TWICE within a couple days, there is a leak, and a large one. It sounds like the sensor is working fine. Level was low, the light came on.

Do you see any drops or a puddle of fluid under your car? Brake fluid just doesn't disappear. How much fluid did the mechanic put in? If it was a good amount I am surprised he let you leave without doing even a cursury inspection to see where the leak was.

How much fluid did you put in? You should get that checekd out right away. Not something you want to be driving around with

xoxbribri

There wasn't even that much fluid missing. The first time on Thursday it was at the "MIN" line and so the guy filled it to the "MAX" line. Yesterday when I stopped it had dropped but not significantly (maybe 2-3mm if that). The strange thing is, I've checked where I've been parked and there is not a single drop of fluid anywhere.

Alfadude

When you put fluid in was the level between the Min/Max level or was it below that? When you added fluid did the light go off?

xoxbribri

The fluid level that I know of has never been below the min level. Both times it was closer to the Max level. As soon as the fluid was added, I had to restart the car but yes the light went off.

catmandoob

The light for the sensor shouldn't kick in until it's below the Min level mark. If it was never there and you are monitoring it with no loss of brake fluid I'd say it very well looks to be the sensor is bad.

I just had a brake line leak and it's not something you wouldn't notice or just walk by and ignore. Also I didn't once have my brake light kick on during the 2 days of driving it with this leak since I kept the reservoir above min. That's just my experience with mine this past week.

xoxbribri

Update: Dropped my car off at the European Service Center next door to my apartment and the guy has confirmed one of the brake lines rusted out! He thinks it is from New England winters with all the salt they put on the roads.

Alfadude

I knew the fluid had to be going somewhere. Glad it sounds like you got to the bottom of it quickly.

catmandoob

That fluid must have been getting caught by the underbelly pan and then blowing off while driving. Glad he found the leak but surprised you didn't see any puddles from it to know sooner.

If he does it right he should inspect the rest of lines since he is already there. On mine it ended up being about a 12 foot run of line going to the passenger rear. Not sure why but that line was rusted and ate up with corrosion something awful while the rest were in decent condition.

timlippold

This is a common issue in New England.