2007 Tarago brake problem

[sticko]

My Tarago has a random brake problem which I can't understand.  When it is used for the first time each day, the brake pedal goes almost to the floor after the first couple of times using the brakes.  Then it is fine all day, with the pedal hard as normal.  When the pedal goes to the floor, the brakes still work, it is just a bit scary if you are not prepared for it.

I have bled the brakes and flushed new fluid right through them and replaced the rear pads which were a bit low.  I was thinking it could be the master cylinder, but it holds good foot pressure when the fading problem isn't there. 

It is a bit of a funny problem, and I have been reluctant to put it in to a service centre as the problem is not always there and would be hard to diagnose if the brakes were working well.

Hoping someone might have some ideas, or has had this problem.

[sticko]

Update on the brake problem.  It was as simple as replacing the brake master cylinder.  I ended up getting an aftermarket one from my local Toyota dealer.  The original one they first quoted was over $600, then this one was $480, and then the spare parts salesman said he could do it for better and sold it to me for $280.

Anyhow I guess the learning out of this is that the faulty brake master cylinder can work good most of the time, but then randomly play up.  Hope this helps someone out with a similar problem in the future.