[RichardJ]

To check booster.
With engine OFF, push brake pedal three times and hold. Start engine and pedal SHOULD drop.

When bleeding the rear brakes, you simply bleed them.


When bleeding the front brakes the Metering valve must be opened. It takes 40-60 psi in the brake fluid to open it. If there is air in the line, you may not have sufficient pressure to open it.
There are two types of metering valves with the one in the second image requiring the pin to be pulled out while bleeding. The other type requires the pin pushed IN and held while bleeding.

It is the job of the metering valve to PREVENT nose under light braking.

Under light, moderate braking, say 200psi from the MC, the metering valve will be open and you will have 200 psi to the front brakes. At slow speeds and you are pressing very lightly on the pedal, the metering valve will close and you will have little or no pressure on the front brakes and no nose dive.

That of course, also means that if the front brakes are not bled properly, you will have little or no front brakes and no nose dive.

Between 40 and 60 psi is the threshold pressure of most metering valves, but it could be higher for some.