hissing sound from brakes

[mcbg]

When the brake pedal is to the floor there is no sound but when I let off the brake it makes a hissing sound (from behind the dash, when I am in the cab)
- is this normal?
The brake light goes off and on intermittently almost always on going uphill.

 

[LCAM-01XA]

The hissing is from the vacuum booster releasing the vacuum, I'm surprised you can actually hear it over the noise of the engine. Brake light coming on can be something as simple as e-brake pedal being a bit loose, I pulled the switch off mine cause I have no e-brake cables and the darn thing kept tripping the brake light all the time!

 

[icanfixall]

The lite can also be telling you the brake fluid is low in the mc resivour....

 

[typ4]

or the vac pump cant keep up with the leaky booster

 

[LCAM-01XA]

vacuum pump failing would have caused him hard brake pedal tho, and it wuldn't care if truck's moving uphill or not. A loose wire somewhere, or a messed up parking brake switch, however, would be affected by the pitch of the truck, probably by the roll as well.

 

[tknomaj]

brake fluid level would be affected by pitch of truck though

 

[LCAM-01XA]

Well yah, but does an '84 have a brake fluid level sensor? Don't think so...

 

[tknomaj]

Your right just check ALLDATA and no level sensor but low vacum sensor

 

[mcbg]

The leak is a vacuum coming from the pushrod in the firewall from the brake pedal. When I put my hand over the rubber plunger for the push rod I can feel the vacuum.

 

[69dieselfreak]

i guess its time for hydroboost then

 

[mcbg]

what are the benefits of hydroboost?
I want to pull a fifthwheel around this summer- so i will need good brakes.

 

[69dieselfreak]

10 times the stopping power and for 5th wheel hauling a must
ive got hydroboost on mine
if you want ill help you set it up it real easy

 

[LCAM-01XA]

Well I wouldn't say 10 times better, but at least twice better

 

[mcbg]

10 times the stopping power and for 5th wheel hauling a must
ive got hydroboost on mine
if you want ill help you set it up it real easy

That would be great- what should I shop around for?

 

[69dieselfreak]

http://www.oilburners.net/forums/showthread.php?t=29836
mlsc has got it down