Brakes - booster or master cylinder?

[MikeB63]

My 09 9-5 2.3t has been showing more signs of age lately and may be coming to the end of the line. I have notices on a few occasions lately that when I start the car and begin to move slowly, the brakes don't seem to grab hard and the car is slow to stop. When I get in, the brake is high off the floor. When i start the car, it moves down a bit. When I start to travel in earnest, the brakes return to normal. The first time I noticed this I stopped the car and checked the fluid level. It was full. When I returned to the car the brakes were fine. I am guessing that the master cylinder is failing, but when I look at the WIS I see there is booster. Can this be failing or would they fail together? The odd thing is that once travelling, all seems normal. Anyone have any thoughts?

[Digger]

Yes master cylinders fail, brake boosters will fail and really should flush the brake fluid at least once a decade or so. Fluid flush is the cheapest possible solution to the sound of this problem.

[MikeB63]

That's definitely worth a try. I've only owned it for 4 years and replaced the rear calipers when I got it. I haven't touched the fronts.