Chrysler Repair: Dodge caravan sport brakes, power brake booster, shock absorber

Question
QUESTION: Brake pedal has little pressure have to hit hard to make it stop, fluid fine, replaced master cylinder and power brake booster here a slight psst noise when depressing brake. any ideas??

ANSWER: Hi Shelly,
If if sounds like an air "psst" I would check the hose between the intake manifold and power brake booster to see if it is loose at either end or pinched anywhere. The sound might also be coming from between the master cylinder and the power booster can which are mated together by a vacuum seal. Did you use a new seal when replacing those units, and made sure the seal sits squarely in the grove of the master cylinder? The nuts that fasten the two unit together are supposed to be torqued to 19 foot-pounds.
Those would be my ideas.
Roland

---------- FOLLOW-UP ----------

QUESTION: Those are fine, the psst noise is comming from underneath the van on driverside, there are no fluid leaks.

Answer
That is an unusual location for such a sound. How about listening to the proportioning valve which is mounted on the left rear frame rail, just forward of the rear shock absorber to frame rail mounting location. If that is bad it can make for excessive effort. I don't know whether it can make such a noise but that is the only thing I can think of on the left underside. Are you working with a helper who can either operate the brakes or listen while you do the alternative task?
Roland