I have an ‘07 Avalon with 179K miles with a push button start - runs and drives great.  Within the last year after sitting overnight, the brake pedal is hard to press down - not so much that I can’t start the car but obviously not normal.  Once I start the car up, no problems with the brake or braking power.

I have changed out the check valve on the vacuum booster but that was not the source of the leak.  Is there any other component other than the brake vacuum booster that would cause loss of vacuum overnight.

Looking at what it would take to put in another booster, I can live with the current issue as it is fairly buried next to the firewall under the master cylinder, behind the air intake stuff, etc.

Any thoughts as to what else would cause the leak?  It doesn’t leak down immediately after shutting the car down, only when it sits overnight.

Thanks and enjoy your youtube channel!

James