Hissing sound

Reinforcements · Post by **Reinforcements** » Sun Oct 30, 2005 10:59 pm

I have this hissing sound that seems to be coming from just behind my brake pedal. When I apply the brake, the hissing stops. And when I get off the brake, it comes back. It doesn't seem to be affecting anything its just really annoying. Can someone please tell me whats going on?

FatMan · Post by **FatMan** » Mon Oct 31, 2005 12:09 am

is it coming from under the hood? may be the vacumm line on the break booster thats the only vacumm line in that area i think.

plowboy · Post by **plowboy** » Mon Oct 31, 2005 6:52 am

The brake booster is most likely going bad. It could be the vaccum line like FatMan said. Check that first. Make sure the line is not cracked around the plastic fitting where it attaches to the booster or that the rubber seal the plastic fitting goes through. In my expierence if the line is good, then the booster will need to be replaced.

Reinforcements · Post by **Reinforcements** » Mon Oct 31, 2005 1:30 pm

About how much will a brake booster set me back?

ranger5.0 · Post by **ranger5.0** » Mon Oct 31, 2005 7:44 pm

It depends on where you get it. You could try taking the vacuum line off of the brake booster and plugging it to make sure if it is the booster leaking. You could also try using a vacuum pump on the booster and see if it will hold the vacuum. One more thing does the engine rev when you engage the brakes?

Reinforcements · Post by **Reinforcements** » Mon Oct 31, 2005 9:07 pm

The engine doesnt rev when i hit the brakes. If I am at idle and I mash the brake hard enough, it seems as though it will die if I keep holding it.

ranger5.0 · Post by **ranger5.0** » Tue Nov 01, 2005 7:09 pm

I would try the other tests then. Especailly the bleed down test on the booster.

plowboy · Post by **plowboy** » Wed Nov 02, 2005 10:07 am

Last booster I bought for my 85 BII was $65 with core and no master cylinder. I think with the master cylinder it was $123. That was at Auto Zone. My 86 has a different size booster that the 85. Haven't had to replace it yet, so not sure if there is a difference in price between the two.

Reinforcements · Post by **Reinforcements** » Wed Nov 02, 2005 12:22 pm

thats not too bad. I think thats what im gonna have to do. I dont have any vaccuum leaks so I think its the booster. That would also explain why I have no power brakes when the truck is turned off. Thanks guys.

ranger5.0 · Post by **ranger5.0** » Wed Nov 02, 2005 6:42 pm

Reinforcements wrote:That would also explain why I have no power brakes when the truck is turned off. Thanks guys.

I don't think anybody has power brakes when the engine is off.

Reinforcements · Post by **Reinforcements** » Wed Nov 02, 2005 10:40 pm

I thought the booster held some vaccumm so if the engine dies or something, you can still stop easily

ranger5.0 · Post by **ranger5.0** » Fri Nov 04, 2005 7:45 pm

Not normally. One some vehicles that haven't been modified and are quite, that is how you can tell the motor is dead by the brakes are harder to push. Maybe if there was a vacuum reservor inline with the booster that might be the case, like in heater controls, but I doubt it.

Reinforcements · Post by **Reinforcements** » Fri Nov 04, 2005 11:39 pm

Ah, alright.