Soggy Brake Pedal

[06YarisRS]

I recently changed my front rotors. Although I didn't do a brake bleed/flush then - I did this fairly recently - I started experiencing soggy brakes. The pedal would almost go to the floor. The car stopped fine, but the pedal was way too spongy. I started poking around and discovered that one of the old pieces of hose I spliced into the brake booster line - to tap into for my boost gauge and blow off valve - had a huge crack in it. While removing that small section of hose, I decided to check the brake booster check valve on the manifold. You could both blow into the manifold and suck air from the manifold. Strange indeed. I expected to be able to blow air into the manifold, but not suck air out. So, either it's not actually the check valve or it's broken. I dug a 3/8" a barbed aluminum check valve that I bought as an extra for my water/methanol injection system out of my junk box. I plumbed that in between the boost/BOV tee and the brake booster. Instantly, my firm pedal returned. As an added bonus, I boosted over 9 psi as opposed to my normal 7.5 - 8 psi. I may have to loosen my wastegate. Getting into sketchy territory at 9 psi with the stock engine.

All this to say, that if you have a spongy brake pedal, check the brake booster check valve. It is unlikely to be a regular failure item on most cars, but in my case, where I'm boosted, the pressure, as opposed to normal vacuum may have killed the check valve.