1995 Ranger, what signs are there that the brake booster may need replacement?

Is it woking or not put your foot on the brake with the engine running? I've found a few that people have lost the reaction disk while changing the master cylinder

if you got to use both feet and stand on the peddle to brake, thats a good sign ...

In theory, the BRAKE BOOSTER and the fuel Pressure regulator can and SHOULD last the lifetime of the car.>>>IN REALIITY, people use WAX BASED OILS like .  In REALITY though, hot acidic OIL VAORS over time will rot the DIAPRAGMS up and VOILA!. It's time for the PARTS STORERS.  Seen this over and over again  THe CURE is the use of most any modern SYNTHETIC oil.. I LOVE PENNZOIL PLATINUM and EURO oils,  They are made from NATURLA GAS< and have ZERO CRUASE OIL in them that contributes the HOT ACIDIC VA{OPRS that rot away RUBBER PARTS< seals and gaskets! To test the BRAKE BOOSTER< remove the vacuum hose to it, and SUCK ON IT. the HOSE that is If you get no RESISTANCE< the diaphragm is good If you CUK ON IT and you continually get AIR< the booster diaphragm is BAD Timf fopt the part store! POWER WASH your engine bay and focus on the space BEHIND the radiator and in FRONT of the AC condenser Here is where bird droppings turd, leaves, feathers and other debris collect over the years! THis will aid COOLING of the engine and help the OIL VAPORS not to from as much! BUT PENNZOIL SYNTHERTICS will prevent ANY ACIDIC HOT VAPORS from, forming at ALL! GOD LOVE this stuff! PENNZOIL gives a remarkable 500,000 mile WARRANTY on the engine if you can PROVE that you usedf it! It's EASY! PENNZOIL makes no waxc, tar, varnish, sludge or COKE and heps the inside of the enigen REAMIN AS CLEAN as on the SHOWROOM FLOOR! HEAT will not cololect>>>it dissipates GOOD LUCK> LEARN from this. THese parts may ROY weith time ANYWAYS> 

Brake boosters practically never fail but they get misdiagnosed and replaced all the time. If you're having a braking problem this very likely the case.

Symptom: 

Reduced or no "power brake" assist.

Test: 

It won't hold vacuum if you evacuate it with a pump.  

(It's leaking because of metal corrosion or a damaged diaphragm). 

Sometimes a master cylinder fails in such a way as brake fluid gets sucked into the vacuum booster.  In that case you'd be running out of brake fluid with no apparent leaks at wheel areas or onto the ground from brake lines. 

-General automotive mechanic since 1972

Hissing sound when applied, filled with brake fluid, leaking out brake fluid, hard brakepedal

The test is to press on the brake pedal hard then start the car. The pedal should move noticeably towards the foot under your foot. If it doesn't or hardly moves at all the assistance is absent.

No power brakes. A sucking vacuum leak noise when applying the brake pedal. It's more likely you have a bad master cylinder or caliper problems if the brake pedal goes down to the floor.

if you got to use both feet and stand on the peddle to brake, thats a good sign ...