hard brake pedal on cold start?

[saadq12]

So I've noticed this intermittent problem recently, when I do a cold start(car parked on my driveway for more than 7 hours) and put the car in reverse, I will feel the brake pedal getting very hard once I release it and press it again, there will be little to no braking effect on the car but once I am off the driveway and put the car in Drive everything works okay.
I am thinking my brakes need to be flushed or there is not enough brake fluid going to the brakes during a cold start(the brake fluid is topped off). Also I did replace all brake pads a month ago.
Any ideas on what this problem could be?
Thank you.

[Charles.waite]

My car does this. Its just that the vacuum leaks out of the brake booster when the car sits and you get a hard pedal until the vacuum pump pulls the vacuum again. Its such a slight issue on my car I've not bothered to remedy it as a new brake booster hose is like $100 and didn't seem worth it tome. Its not a mechanical issue so it doesn't present anything with general safety. If it really bugs you or if the leak is big enough to affect vacuum assist while driving then I would look into replacing the booster hose. Or even just splicing in a check valve to curtail the leak, assuming its coming from the hose or vacuum pump.

[saadq12]

Thanks for the reply and info. Yeah it doesn't bother me too much since it only hapens on cold starts but I was just concerned for safety reasons obviously. Do you happen to have a forum/DIY link to diagnosis this problem further?