Brake Pedal Hard Before Starting: 2004 Toyota Tundra Limited

So this is an interesting one. I have noticed recently that my brake pedal is hard before I start the truck, and it is fine after. It was not like this before. Yes, I know that if you pump the brakes with the truck off it will build up pressure, but it's weird that is is always hard before starting. It only happens if I leave the truck off for more than 10 or so minutes. I am just concerned it is going to turn into something worse. Any ideas? Has anyone had this happen before?

The truck has 64,000 miles on it now...

 

the booster may have a small leak and looses its vacuum when its off. (or the check valve if these have that, i dont remember

 

It's interesting, this just started happening on mine within the last 6-8 weeks. The only maintenance I've done since it started ... I had front passenger side torn down to this point, then re-assembled. Didn't really touch the brake lines or caliper though, which left me scratching my head. Still no clue wtf is going on. Not seeing any leaks or anything loose anywhere. Looks like .

I'd ask @JMHA1997 if his happened after installing his leveling kit, but looks like he hasn't logged in since posting this thread.

I'm going to try replacing the check valve. For my '06 AC Ltd it looks like the check valve p/n is 4473030050 and the grommet that holds it in place is 9048024015. WTF this is a basic check valve and MSRP is over $65, street price is like $45. How in the hell?! And the weird part is, EPC-DATA.com is showing it as an $18 part. Bizarre.

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