I've had some issues with this 1998 cherokee classic 2x4 auto without ABS lately.

I've been bleeding this cherokee like a pig lately to get some pedal but to no avail. the brake pedal has been pretty terrible before but now i can't even get any brake. I have replaced the master cylinder, brake booster, wheel cylinders in the rear, fluid reservoir, and pads in the drums. i also took the rear lines off to see if there's any trash and blew a little air in it.

when starting the car with the 1st pump of the brakes the light comes on. after two deep pumps it shuts off and i continue pumping and bleed it. after bleeding it the same thing happens. the pedal is weak and slightly firms up. what i notice is if i pump till the light turns off and leave it alone i hear a low idle sound. about 3 seconds of leaving it alone i pump again and the pedal weak and the light comes on again. seems to be some vacuum issue. i have no idea what i can possibly do to get some brake pressure.

 

Seeing any leaks on fluid? Spongy pedal is usually air in the lines. How do they look? Any leaks or ballooning?

Second, how are the drum adjusters? Sometimes if they have been stuck or rusted they don't work, which will usually give you a low pedal but may feel spongy too. There are a bunch of threads on adjusting them.

If you hold your foot on the pedal, engine running, does it slowly go down? Cause that's usually the master cylinder not holding pressure.