Brake Hiss/no Pressure/terrible Brakes......

[Kubic40]

1988 mj

 

So the brakes suck haha......i've bleed them to no fix.....pedal goes to the floor no matter how mant pumps with truck on or off.......no fluid leak from calipers or drums.....fluid levels are good still.

 

hissing noise both on compressing and rebound of pedal......brakes only work and barely at that when the pedal is smashed to the floor and I'm no skinny twig by anymeans.

 

I'm assuming the brake booster/master is bad and needs replaced?

[HOrnbrod]

Probably a blown diaphragm in your booster. Use a piece of heater hose and listen at the booster while a helper is working the brakes with the engine running to localize the hissing. Also pull the check valve at the booster vac hose connection and suck and blow to see if it works.

[yellaheep]

After running the truck for a few minutes, turn it off and return after 10 minutes. Twist and pull at an angle on the plastic valve that pops into the booster.  You should get a hiss of air as the vacuum is released.  If not, the booster and/or the check valve is bad as it's not holding vacuum.

[ownedueasy]

I'm having the same problem, after pulling the plastic angle plug there's air coming... Anybody know if a booster from a 2.5/4.0 Cherokee will work? My booster is the plunger type and it's got a new master on it..