i have a 1990 cherokee 4wd 4.0 I6 no abs brakes.

when driving I was sitting a stop light for a couple minutes and the brake slowly went to the floor and the red brake light came on. The light turned green brake light stayed on but the brake returned back up and then once stepping on the brake the light went away.

I pulled over to the next chance I could and checked my brakes to see if anything was leaking and saw nothing and then checked the master cylinder and it was full.

I've replaced the rear steel brake lines. Front rubber lines and both calipers. Also replaced the master cylinder.

Any ideas or things I need to worry about? i've had previous problems with the brakes in which the brakes are mushy and got o the floor.

 

Did you check the inside of the rear wheels for fluid? If the wheels are wet then your rear wheel cylinder is bad. Try bleeding the brakes. Start from the furthest from master and work your way to closest.

 

ah forgot to mention i put in brand new wheel cylinders, shoes, springs, and self adjusters so i would really hope its not the wheel cylinders but i will have to check that, I didn't see and fluid coming out of the drum during my initial check

 

try looking into getting a new brake booster

 

i was contemplating that, if i would i would do the dual diaphram brake booster upgrade i think. Would it be worth getting a new one for a new cherokee for getting a junkyard one?

 

Don't think it's the booster. If the pedal goes all the way to the bottom it;s one of two things:

If you don't lose any brake fluid, it means the master brake cilinder is shot. Essentially there's internal leakage from one end of the piston to the next. Don't know if you can get overhaul kits, but I would just replace it with a new one.

If you lose brake fluid you have leak somewhere. You should check for brake fluid at the front brakes (easy) or the rear brakes. Takes a bit more work as you really need to take the drum off. W

Jeroen

 

I have seen the abs dump valve go bad alot on chevys. It is basically the whole abs module. Cause the same thing. But it is much more common for the mastercyl. to go bad. BUT if your brake light is coming on, AND the fluid lvl is good I would lean more towards the abs module

 

well i double checked all the lines and the drums there isn't a leak anywhere, must the be master cylinder but I just put in a new one about a month ago.

possibly the brake booster?

maybe i should just get a dual diaphram and master cylinder together not exactly sure where the best place for that is any ideas?

 

on ebay i found a 97 dual diaphragm brake booster, master cylinder, and proportioning valve for $55 with shipping, what a deal right?

anyway installed it today following "https://www.cherokeeforum.com/f51/xj-brake-upgrade-3352/" and any problems i had were definitely solved.

things that weren't mentioned in that article though is that in moving the windshield washer fluid up you need to splice in some extra wire to make everything reach. same with the brake fluid light one the proportioning valve.

braking has definitely improved but the pedal being so far forward is a little awkward . . . have yet to go on a significant drive where i got used to it.

 

I agree with a couple of guys here... it sounds like it's the master cylinder. I could be leaking out into your booster. Kinda a common problem is for the master to fail and leak into the booster.