Power brake booster

I have a new 2019 Tacoma TRD Sport. It has the Push-Start button which is new for me. I must press on the brake pedal before I push the button to start the engine. What I've noticed is that if the engine has not been started in two days or more the power brake booster has lost its vacuum reserve. In this case I have to press much harder on the pedal to start the engine. A message will appear during the start that tells me there is a brake malfunction.

No hissing is heard while operating the vehicle and it has very good brake performance. Once started I can restart it all day long without noticing the stiff brake pedal. But if it is unused for more than two days there will be a stiff pedal. After shutting the vehicle off there is 8-9 power assist brake applications available. These gradually disappear over the next two days.

My 2014 RAV4 will have 5 power assist brake applications after sitting for 10 days.

My concern is that the booster may be defective. Or at least heading that way and where brakes are concerned I'd like to be sure. I've taken it back to the dealer but they want to keep it a few days (like I'm fibbing to them - now days everybody wants a new brake booster, right?) They ran a test and couldn't find anything wrong the one time I let them look at it.

Can anyone tell me if they have noticed that their power brake pedal is stiff within a couple days of last using the vehicle.

I worked as an auto mechanic most of my working years and have done loads of brake work. I am familiar with brake systems.

Ray

the one way valve in the booster system could be leaking. not sure if its in the hose or the booster

the one way valve in the booster system could be leaking. not sure if its in the hose or the booster

I've plugged the hose at the booster but that didn't help. The check valve seems to be a much smaller thing then it use to be. Different design maybe. A few weeks ago I started lifting the brake pedal with the toe of my shoe before exiting the truck. It seems to be holding vacuum a bit longer - like yesterday, I got into it after it had set unused for almost 3 days and found it had several brake applications still in it. I will post back if I find for sure that the situation has changed.

Thanks

Good News! A few weeks ago I started pulling up the brake pedal with the toe of my shoe after parking the truck for the day. Never heard or felt anything but it seemed to me that something was changing. Today, I found that there were 4 1/2 power assisted brake applications available after the truck had set unused for 3 days (before starting the engine). So, after 6 months I can finally get into my Tacoma and start the engine without having to push like superman on the brake pedal.