Car is a 2006 Elantra. If the ambient temperature is below 70 degrees the brake pedal goes down 2" before encountering resistence. If the ambient is above 85 the brake pedal only goes down the appropriate small amount. This is for initial startup. After the car is driven about eight miles the brake pedal is normal regardless of ambient temperature. I'm thinking master cylinder where the seals work better when warmer but I've never heard of this happening. Anyone had any experience like this? Could it be anything other than the master cylinder?