Went out to cruise this afternoon and noticed my brake pedal sinking towards the floor. This happened three times in a span of about 10 minutes. I was able to pump up the brakes and they held just fine. No further problems during my 40 minute cruise. I looked at the inner sidewalls under the truck all dry and no puddles. I had the front wheel bearings repacked and the drums turned, wheel cylinders and shoes all 4 wheel complete inspection about 3 months ago. I topped off my master cylinder about 9 months ago. What should I do next, could this have been a simple problem of air in the line or symptoms of something else, thanks HUGH
