The Nissan Path

Brakes are hard , require really firm pressure to stop , but it does stop . Before i just replace the brake booster , what is the diagnosis process ? And , could it be the check valve ? And how would I verify that ?

Brakes do work , but require incredible effort to push the pedal to get it to stop.

Thanks for any help.

Hard brake pedal is typically a booster issue. Disconnect the hose from the engine to the check valve and there should be plenty of vacuum there (it should stall out the engine unless you block it off quickly). The check valve is a one-way device. You should be able to blow through it one way with your mouth but not the other way. If the diaphragm is leaking, you will often hear the air leaking under from under the driver's side of the dash. It's also a good idea to make sure none of your brakes or the emergency brake are improperly adjusted or locking up.