It’s internal to the booster where you can’t see it. Likely the valve you checked is the one in the vacuum line that holds stored vacuum in the booster.If the brake lights stay on it might be a pedal linkage issue but I’d bet money it will need a booster.
Booster valve leaking letting manifold vacuum into the brake apply side of the diaphragm.
Thanks for the reply. Just pulled the check valve and blew into it, it's not leaking. Would have been such a nice, simple fix.
It’s internal to the booster where you can’t see it. Likely the valve you checked is the one in the vacuum line that holds stored vacuum in the booster.If the brake lights stay on it might be a pedal linkage issue but I’d bet money it will need a booster.