Brake Booster troubleshooting

[AussieCJ7]

I think I know what the issue is but want some guidance

Brake peddle feel with engine off is good all new rear drums and hardware

Start the engine and peddle feel goes soft and while it pulls up pretty well when you stand on the brakes it has a spongy feel that doesnt inspire confidence

I think it is a vacuum problem and mostly likely the booster diaphragm but what is the best way to confirm this before wasting $$ on new parts

 

[mtnwhlr]

A soft spongy pedal is air in the brake lines. It sounds like you need to bleed your brakes. With the brake booster you either have power beakes our you don't.

 

[AussieCJ7]

A soft spongy pedal is air in the brake lines. It sounds like you need to bleed your brakes. With the brake booster you either have power beakes our you don't.

Brake feel is good with no engine ie no booster and no vacuum

 

[Torxhead]

A worn brake booster will release vacumn to the outside and stall out the engine when the brake pedal is depressed. Keep bleeding the air out, you probably have let the fluid drain out all the way to the proportioning valve.