I replaced both rear drum brakes and front disc brakes on Saturday, after everything was finished and we bled the brakes they were still soft and spongy going down to the floor and needed to be pumped for the vehicle to stop. I then replaced the master cylinder but the problem still exists (the brake fluid is full and there are no leaks). What could be the problem?

 

Flush the ENTIRE system, the brake fluid probably has water in it.

 

check your fluid levels first. If your brake fluid is fine and you did a good job of bleeding your lines, your master cylinder might need replacing.

 

I'm assuming that you haven't replaced any other hardware such as the calipers as you didn't mention that. If you did, I'd consider possibly having the wrong calipers on the wrong sides. Bleeders have to be up for this to work. You'd be surprised how many people have done this, including me once on a Subaru.

If no new parts other than you stated have been replaced, I'd start with flushing as stated. If this doesn't fix it, then I'd look for some sort of leak somewhere, either maybe in a bleeder screw not tightening up properly or a cracked line (you'd see fluid dripping out somewhere if this is the case) or a wheel cylinder possibly. I'm curious as to why you had to bleed the brakes at all if you just replaced pads & shoes.

 

Thanks guys! I will try flushing it all out =) I already replaced the master cylinder!

 

You have to bleed the furthest brake to the closest. RR, LR, RF then LF.

 

X2 ^^^

Do it right the first time lol

 

X3

 

A bad brake line can balloon and cause a mush pedal.

 

1996XJSport: I want to buy your 92 laredo. How much you want for it? Lolol

 

I'm currently having this same problem. I replaced a caliper and rotor with new pads. I turned the other rotor with new pads. I replaced the rear shoes and wheel cylinders. I even bled the master cylinder. I get brakes if I pump up the pedal. The brake fluid pressure sensor in the proportional valve was leaking, so I just disconnected it and plugged the hole. There's no leak there or anywhere else. How do you flush the brake system?

 

Abs system comes to mind. Didnt the earlier cherokees have a problem with them? Is the brake pedal rock hard with the vehical shut off? and did you bench bleed the master?

 

did you bleed it with it on or off? last time i checked these had vacuum boosters and needed to be running to fully bleed them.

 

Does not Need to be running to completely bleed the brakes.

OP....by any chance did you replace the calipers when you worked on the front brakes? If you did, is the bleeder on the top of the caliper or is it on the bottom? If you answer with "bottom" then that is your problem, mounted on the wrong side.

 

Often caused by the rear shoe adjustment being too loose.

Tighten them till the wheel doesn't turn, step on the pedal to center the shoes, tighten again.
Then back it off 4 or 5 clicks, step on the pedal again to center them, if still too tight, back off another 4 or 5. Repeat, - center the shoes every 4 or 5 clicks.

most folks set them waaaay too loose. Pedal feels spongy all the way to the floor.