A couple of times in the colder weather my brake pedal was harder to push until the car warmed up, a bit nerve racking when it hits by suprise. I'll do the usual bleed but any other experiences?

 

I have this is my DD ram as well. My rotors and my pads are pretty worn, so I just assumed it was due to this in one way or another.

 

I would assume it's an issue with the hydraulics, probably master cylinder.

Whether it's a symptom of something serious, I don't know.

Dave

 

Could the vacuum check valve stick when cold?

 

Follow up:
The problem was the check valve which was "taken care of" at a Mazda dealer as part of the brake recall previously. So in their wisdom they left the old check valve hose on the passenger side and just added the new one on the drivers side on top of the booster. Effectively having two check valves in series - a crappy old one and a new one.
I ordered the hose kit from Ray (has new hoses for both sides with the check valve only on the drivers side) and replaced both sides today. Result - no more problems so far.