Brake hissing? Vacuum line sound?

[Egm89]

1987 4.0 swb 5spd 2wd

Helo fellas! I got a question regarding my brakes, they making like a "hizz" sound from inside the cab when the brake its depressed, sort of like a vacuum leak would sound. But when I press on the brake, the "hizz" sounds, dissapear.

here's a video of it, it starts with the hissing, and when I press on the brake the iddle lowers a bit too (I have dummy lights, so not sure on the rpms).

[cruiser54]

Probably best to isolate the source of the hiss first. Pinpoint it. 

 

That said, your booster or the one-way check valve in the rubber grommet is bad. 

[Egm89]

Probably best to isolate the source of the hiss first. Pinpoint it.

 

That said, your booster or the one-way check valve in the rubber grommet is bad.

Well from under the hood I can't hear anything bad, sounds pretty normal, but from inside the cab, like around the pedals area, it sound like a "hizz", that only dissapears when I step on the brake, and I can ever hear it dimishing as I step on brakes harder. The truck stil stops and everything, but Imma go check the valve and the groomet. And if its not that, time to upgraxe to 95-96xj brake booster right?

[cruiser54]

 

Probably best to isolate the source of the hiss first. Pinpoint it.

 

That said, your booster or the one-way check valve in the rubber grommet is bad.

Well from under the hood I can't hear anything bad, sounds pretty normal, but from inside the cab, like around the pedals area, it sound like a "hizz", that only dissapears when I step on the brake, and I can ever hear it dimishing as I step on brakes harder. The truck stil stops and everything, but Imma go check the valve and the groomet. And if its not that, time to upgraxe to 95-96xj brake booster right?

 

Actually 99 to 2004 WJ booster/master swap has more advantages. 

[Egm89]

 

 

 

Probably best to isolate the source of the hiss first. Pinpoint it.

 

That said, your booster or the one-way check valve in the rubber grommet is bad.

Well from under the hood I can't hear anything bad, sounds pretty normal, but from inside the cab, like around the pedals area, it sound like a "hizz", that only dissapears when I step on the brake, and I can ever hear it dimishing as I step on brakes harder. The truck stil stops and everything, but Imma go check the valve and the groomet. And if its not that, time to upgraxe to 95-96xj brake booster right?

Actually 99 to 2004 WJ booster/master swap has more advantages.

Is it still bolt on? Or I have to adapt it?

[cruiser54]

 

 

 

Probably best to isolate the source of the hiss first. Pinpoint it.

 

That said, your booster or the one-way check valve in the rubber grommet is bad.

Well from under the hood I can't hear anything bad, sounds pretty normal, but from inside the cab, like around the pedals area, it sound like a "hizz", that only dissapears when I step on the brake, and I can ever hear it dimishing as I step on brakes harder. The truck stil stops and everything, but Imma go check the valve and the groomet. And if its not that, time to upgraxe to 95-96xj brake booster right?

Actually 99 to 2004 WJ booster/master swap has more advantages.

Is it still bolt on? Or I have to adapt it?

 

Easier than the 95 to 96 and more readily available. 

[Egm89]

 

 

 

 

 

Probably best to isolate the source of the hiss first. Pinpoint it.

 

That said, your booster or the one-way check valve in the rubber grommet is bad.

Well from under the hood I can't hear anything bad, sounds pretty normal, but from inside the cab, like around the pedals area, it sound like a "hizz", that only dissapears when I step on the brake, and I can ever hear it dimishing as I step on brakes harder. The truck stil stops and everything, but Imma go check the valve and the groomet. And if its not that, time to upgraxe to 95-96xj brake booster right?

Actually 99 to 2004 WJ booster/master swap has more advantages.

Is it still bolt on? Or I have to adapt it?

Easier than the 95 to 96 and more readily available.

As in everything, you are probably correct, following ur advice.

Thanks cruiser!

[cruiser54]

 

 

 

 

 

Probably best to isolate the source of the hiss first. Pinpoint it.

 

That said, your booster or the one-way check valve in the rubber grommet is bad.

Well from under the hood I can't hear anything bad, sounds pretty normal, but from inside the cab, like around the pedals area, it sound like a "hizz", that only dissapears when I step on the brake, and I can ever hear it dimishing as I step on brakes harder. The truck stil stops and everything, but Imma go check the valve and the groomet. And if its not that, time to upgraxe to 95-96xj brake booster right?

Actually 99 to 2004 WJ booster/master swap has more advantages.

Is it still bolt on? Or I have to adapt it?

Easier than the 95 to 96 and more readily available.

As in everything, you are probably correct, following ur advice.

Thanks cruiser!

 

I've done booster conversions using 95/96 and 99 to 2004 Grand Cherokee. Prefer the latter.