Does this indicate a problem?

[Alan_nc]

So you are sitting in the vehicle getting ready to start it for the first time of the day. Put your foot on the brake (it's at the normal level) and turn the key. Brake pedal goes all the way to the floor. Comes right back up as soon as the engine starts. Never does it again for that day and there doesn't seem to be any problem with the brakes.

 

[RonD]

Usually not an issue, your Booster is losing vacuum after sitting awhile most likely
When you start to crank engine over you get about 2" of vacuum then 18+" when it fires, and with vacuum assist pedal goes down "almost" to floor if you were already pressing down on it

Start engine then shut it off
Press brake pedal down 3 times
You should have vacuum assist for 3 pedal presses then pedal will get hard to press down, vacuum is gone
That's normal, so safe, the booster is large so if engine should stall while driving you can safely pull over and have power assist brakes to stop vehicle

In theory you should have that same 3 pedal presses days later, without starting engine, but there can be leaks in check valve or diaphragm

If you are not getting 3 full pedal presses, engine off, then you may want to replace booster(with new check valve), when you can find one on sale

 

[Alan_nc]

Thanks. I thought it indicated the brake booster. I'll watch for sales or a coupon. Don't think it's a good idea for this to be a junk yard item.