Mushy Brakes in Reverse

[MWilley1]

I've got a weird problem that's popped up. Every once in a while especially when in reverse I get mushy brakes to the point where have to get the pedal to the floor to get it stopped. It's almost like the brakes if your coasting in gear with the engine shut off, pretty dangerous anyone have any thoughts on this one?

[Thomcat]

Check for proper fluid in reservoir. If low or empty could be a leak. Spongy pedal is likely air in system.

 

If level is OK, with engine running keep firm pressure on brake pedal to see if it remains high and firm, or if it very slowly drops to the floor. Dropping pedal is likely internal leak in master cylinder.