looks to be this way

Holy crap... I'll go get my books, so there can be an actual diagnosis done.

that is what happened to my MC and others, the seal goes bad and then the brake fluid leaks down the Booster. There is a rebuild kit avaiable, but it is easier to replace the MC.

Okay, Here'* some tests you need to do.

1)Leave the car off, press the pedal a few times to deplete the vacuum tank
2)Press the pedal with as close to 100lbs of force as you can.
3)The pedal should only go down 2.25 in. How far does it go? Is it solid feeling? Does it keep sinking?

1)Refill the reservoir. Wipe down the MC and res with a clean rag.
2)Find someone to press on the brakes as hard as they can.
3)Find the leak.


The reason the "BRAKE" light would come on when accelerating during left hand turns is because of the position of the fluid level sensor. You got early warning, Feel lucky.

I was lucky and got an early warning from my Bonne when my brakes failed.. the wear bar on the brake pad broke off and two days later my brakes started grinding when i came to a stop... but then 150$ and i was back in business (new pads and new rotors)

deffinetly im thankful for some of the things that are on these Bonnevilles

I wouldn't just jump on a new MC. It went bad on my car, and I found out because the same light and tone. But also keep in mind that I had a bunch of other stuff that needed to be replaced as well. I need all new brake lines. I needed 2 new wheel cylinders. The master cylinder. And two new rotors. Do the tests that damemorder told you, because it is very possible that it is just a line that is leaking, and it is spraying onto the booster. I am not saying that it isn't the MC, because it very well could be. But it could be something minor like a line leak, or something major like me.

yea i forgot that the wheel cylinders also go bad

my car had the same exact symptoms...I does meen your brake fluid is low, but dont assume its yer master cylinder...take it to a mechanic and have him do a full brake evaluation, for a cost of 15 bucks or so they will tell you EXACTLY what is wrong with your car. I just had a mechanic at work look at mine and it was leaking fluid from the rear wheel cyliders...so new cyliders and shoes and the problem was fixed (like $170 for good quality parts and labor) if there is fluid below the master cylider it doesnt meen it came from the master cylider.....think back to your last oil change....did you do it yourself? If not there is a possibility the brake fluid was low when it was brought in and they topped it off spilling some down the sides and making it appear to leak, Im not ruling out the master cylider, but it would sure suck to spend the bucks to get a new one spend 2 hours puttin it in to find out the problem will be back in 2 weeks.