The brake pedal on my 2004 Tundra sometimes travels nearly to the floor. It is intermittent and quite unnerving. Once I let up on the pedal and press again, pressure is restored. The reservoir is full, but the fluid is very dirty looking. Would dirty fluid cause this behavior or do I have air in the system? I used a turkey baster and removed all the old fluid out of the reservoir and replaced it with fresh fluid this past Saturday and it is already looking dirty again. I replaced both calipers and both rear cylinders last year, at which time I bled everything pretty well. At least I thought I did.

 

Sounds like air in the system somewhere. I'd double check all along the way for any leaks and the bleed them. I've never had any issues with dirty looking brake fluid. The only time I ever had the fluid be the culprit was once when the fluid boiled - which made it almost useless.

 

I was having issues with the front rotors and calipers last year. They got as hot as 800F, so I suppose that could have boiled the fluid huh?

 

I've had air in the lines lead to a spongy feel to the pedal, but intermittent, to the floor movement would have me suspecting the master cylinder.

 

I'll check for leaks at all four wheels. If I don't see any, then I'll suspect the master cylinder. I've never replaced one before. Is it fairly straight forward? Even though it is intermittent, I suppose I should refrain from driving the vehicle until it is fixed?

 

Usually the toughest thing about installing a master cylinder is bleeding it. Most recommend bench bleeding but I've always been able to do it after installation. Don't forget to check all the brake lines for leaks!