Brake pressure noise?

[Metlic53]

90 cherokee, the brakes work okk...the back drums are gone i'll fix that but when i push the brake pedal it will sound like air is leaking out somewhere constantly, maybe busted brake line? i haven't checked yet, but if i hold the pedal down as hard as i can the air noise goes away.
Thoughts?

[4.3LXJ]

That is actually air leaking in. If it is a constant hiss, rather than momentary, then you have a leak in the vacuum diaphragm.

[PolarXJ]

x 2

[BrianXJ]

That is actually air leaking in. If it is a constant hiss, rather than momentary, then you have a leak in the vacuum diaphragm.


Vacuum Diaphragm? Where is it located in the Booster?

[bigjim350]

Yep sounds like you need to replace the brake booster

[XJ4IV]

my first XJ had that SAME issue and I remember that it didnt effect the ... LACK of functionality i guess but I did replace the booster at one time in an attempt to improve the braking system... which STILL sucked but the noise did go away!

[Metlic53]

my first XJ had that SAME issue and I remember that it didnt effect the ... LACK of functionality i guess but I did replace the booster at one time in an attempt to improve the braking system... which STILL sucked but the noise did go away!

ya im sure its the booster, it doesn't really affect how it will stop, it'll lock up the front if i slam them on real hard, i'd like it better but i wont be daily driving this one as much as my white one so i'll fix it later on down the road. the sound is just annoying sitting at a long stop light.
Hows the dana 60 swap going?

[4.3LXJ]

Unless the leak is real bad, it will still stop for you. One thing you can do is use a ZJ double diaphragm and improve your braking. It takes slight modification, but very doable.

[XJ4IV]

ya im sure its the booster, it doesn't really affect how it will stop, it'll lock up the front if i slam them on real hard, i'd like it better but i wont be daily driving this one as much as my white one so i'll fix it later on down the road. the sound is just annoying sitting at a long stop light.
Hows the dana 60 swap going?

at a light... put in park! 60 swap is a goin got the front axle two weeks ago and also ordered and recieved the front brackets for the coils n such, just need upper arm mounts and rear leaf perches and shock tabs for rear axle and drive shafts n wheel spacers...

[Metlic53]

at a light... put in park! 60 swap is a goin got the front axle two weeks ago and also ordered and recieved the front brackets for the coils n such, just need upper arm mounts and rear leaf perches and shock tabs for rear axle and drive shafts n wheel spacers...

why would i put it in park when i can put it in neutral? :stars: :D
thats cool, shes coming along

[BrianXJ]

why would i put it in park when i can put it in neutral? :stars: :D
thats cool, shes coming along

In park so you can take your foot off the brake

[Metlic53]

In park so you can take your foot off the brake

i know that...but in neutral i could take my foot off the brake too, just hold the e brake barely

[LizardRunner]

It's probably caused by a leaky mastercylinder leaking fluid into the booster diaphram as already mentioned. I have that problem for now, but it still stops quite well for me. The fix is a new master cylinder and booster install. I'm going to put in a dual diaphram booseter as was suggested above, along with the new mastercylinder.

[BrianXJ]

will the XJ master cylinder work on the ZJ booster

[LizardRunner]

part numbers for the master cylinder are the same. It's the same master cylinder, just a different booster and that means a little simple fab work at the pedal connection and maybe the fire wall. having looked at one for a 98 ZJ, they look just about the same everywhere.