I have a 94 dakota 5.2 litre 4x4. Ocaisionally the brake pedal will go to the floor. After releasing it ad hitting the brakes again it will be fine. Soemtimes I will have to pump them once or twice first. Seems to only happen in cooler temperatures.

Any ideas?

Bad master cylinder would be my bet.

You can get a rebuild kit, or a whole new one for around $150.

Guess I should have included that the master cylinder, front calipers and rotors are all new.

Take the master back it is a dud

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88 2.2 5SP
95 5.2 Mag
A518
8 1/4
Electronic ignition
Custom EFI (megasquirt 2.2)

Have you bled the brake lines for air?

Yes, in fact the master cylinder was bench bled and we went through an entire large bottle of brake fluid. There is no air in the lines. It's an intermittent problem, tat's what has me stumped. I'v never known brakes to only be goofy sometimes, either they work or they don't. But mine ...eh they work most of the time but wen it's cooler they don't always.

Hmmmm...

Brake booster?

check adjustment of rear drums, if they are not adjusted there is a big gap between the shoe and drum
possibly bad proportioning valve

brake booster, rear wheel brake cylinders could be leaking. I had that problem with my '90 dak and the rear cylinders had come entirely apart and were puking fluid all over my wheels