bad master cylinder?

[rtcc]

ok, I have an 00 tundra with 220K on it and today the brake pedal started feeling really light. I pretty much had to push it to the floor to make it stop. I looked under the hood and the brake reservoir was empty. So I refilled it but after about 20 minutes of driving it goes empty again. There is no major leak and only a slight oil residue going down the master cylinder. I can also hear a strong air pressure noise coming from the master cylinder area that changes with pedal pressure.

So I guess my main question is what all do I need to buy? I not that familiar with the differences in the master cylinder versus just the brake booster or something like that.

I upgraded to the new calipers about a year ago and everything has been fantastic but I think this is just a high mileage problem.

thanks for any help you guys can give me.

[fredkolias]

I just bought a new master cyclinder for my '00 also. From Advanced Auto it was about $189 new, included a reservoir. It is very easy to replace, just two bolts that hold it on. They had rebuilds available for about $120, but I heard a rebuilt master cylinder is not really a good idea.

The master cylinder attaches on the brake booster, but a new booster is not needed, unless you have a problem with yours.

[los211]

From your description its sounds like you have a leaky master cylinder piston seal. This will leave a trail of fluid down the brake booster. Also the fluid that leaks into the booster will eat at the rubber diaphram over time and cause a vacuum leak which is probably the noise you hear when you step on the brakes. I would replace the master cylinder and the booster.