Odd cold weather brake issue

[covertaxn]

I have an 08 limited 4x4. When it's cold out, like below 25, when I press the brake pedal after starting the engine, the pedal will go all the way to the floor. After pumping a couple times it's ok. It also happened once before driving on the freeway (cold outside) but they were fine after a couple of pumps. Never an issue when it's warm out. Anyone else have an issue like this? Might there be some air in the lines? Brake performance is fine otherwise.
Thanks!

 

[JUST4FUN]

Its not normal for the brake peddle to go to the floor at anytime have it checked out

 

[covertaxn]

Had to dealer twice-claims found no problems- "unable to duplicate"

 

[stamp11127]

The dealer is an idiot. I'd suspect the master cylinder is giving up the ghost. How many miles are on the vehicle and what is the color of the brake fluid when looking through the reservoir?

 

[montecarlo31]

The dealer is an idiot. I'd suspect the master cylinder is giving up the ghost. How many miles are on the vehicle and what is the color of the brake fluid when looking through the reservoir?

another vote for the master. We just had a salesman have a 100% complete brake failure of the master and he lost all braking power in his F-150, guess what, it's not an uncommon failure on these trucks.

 

[covertaxn]

110K. It's odd that this never happens when it's warm. Had brake fluid replaced at 85k.
I'll change the master cylinder.
Thanks all!

 

[GAINMOB]

my master cylinder went and that is what happened...ALSO...my ABS module went out and the same thing happned...so check both...when my ABS module went out brake fluid was leaking with every pump of the brakes...

 

[covertaxn]

Thank you sir! No fluid leaking yet.