brake booster problems

[Crazythingsido2]

i thought my brake booster was bad so i replaced it. it sounded like it had a vacume leak and it "hissed" inside the car. and when i was on the brake it was making my idle rise.
i put a new one in and its still doing the same thing.
what could it be?

 

[rubmehard]

hey man im having the exact same problem with my 1994. exact same symtoms only when i pump the brake it wants to stall out. replacing the booster was my next option. did you find out what was wrong

 

[Zach19Dude]

is it still hissing or is it just making the idle rise ?? it could be a hose or the check valve

 

[redeyed]

What's up all! I have the same problem as this. I have a steady hiss that when I hit the break gets louder, the harder I push on the peddle the lower the rpm's get until the emgine cuts out. With the engine running I still get the hiss but the truck idles just fine and it does'nt get louder apon accelereation. I checked every vaccume line on the whole engine three times and they all seem to be in perfect condition. In general these trucks are easy to tear into but this ones got me stumped.

 

[redeyed]

I was pulling fire wood out of the woods, which these old trucks kick ass for, and I noticed that when I'm low range the hising seems slightly louder and dies out sooner when I hit the breaks. I love this truck and would love to figure out what the hell is going on. I just don't know what the hell to do, a vacume leak is a vacume leak and I dont like them

 

[Mark_88]

The booster acts on a vacuum line from the engine, so if there is a leak you are loosing vacuum, which can affect idle and fuel suction (the suction is actually caused by the intake cycle of the piston so if there is a leak, less or no fuel gets taken into the cylinder for compression/combustion)....

Check for other disconnected or broken lines on the engine...such as those into the intake side of the engine...the pcv line is a prime suspect on later models, but carbed engines have many vac lines to check sometimes...\

And you can check the tube going from the vac tree to the booster...look for leaks or loose connections (i use hose clamps on both ends) and that the plug going into the booster is tight...also make sure that there is slack in the tube because if the engine rocks it could yank the tube out of the booster...

I've replaced boosters for the same noise, only to find out it was a vac line problem...

 

[redeyed]

I'v checked over and over the only thing I can come up with is that the check valve seams to move around alot. Can I just pull it out and replace the worn out grommet?