1994 Cherokee, Country, 2WD. I bought it new, has 270,000 miles. It's not my daily driver but still in great shape. I have been slowly trying to solve for brake pedal going to the floor over the past couple years. It's drivable, but the pedal is soft and can go all the way to the floor. I have replaced virtually every part of the brake system trying to solve this issue: master cylinder, pads, rotors, wheel cylinders, hoses, proportion valve, booster, front calipers. It seems to not have any, or very little, rear brakes, so the pedal travels, then engages what feels like the front brakes. There are no visible fluid leaks and never have been. I solo bleed the system using a hose dipped into a jar of brake fluid, opening the bleed screw and pressing pedal until all air is out of the drain line. My brake light never comes on, even though pedal goes to the floor. I have adjusted the rear shoes to the point where they rub too much and get hot, and then backed them off just slightly. I also felt the push pin was long enough to rapidly engage the master cylinder and adjusted it to be longer such that it is depressing the plunger in the master cylinder.

One part that has me a little baffled is the brake line junction on the rear axle. Pictured below. This square junction has 4 lines, one is fluid feed line, two lines branch off to go to each brake drum on the rear,. But, there's a fourth rubber hose line that goes upward and disappears into the frame rail. I assume this is some sort of vacuum line, but I can't tell where it goes to. I wonder if I'm losing some sort of vacuum or if there's a way air leaks into the system (even though no air is observed in the system when I bleed the brakes). Since this junction feeds the rear brakes, I wonder if it's the culprit. I realize the replacement parts I've installed are likely Chinese junk, but if the master cylinder were bad, wouldn't it be leaking fluid? It is new and show no signs of fluid leak.

Any ideas or feedback is greatly appreciated.

 

As for the rear line junction block, the line that goes up is the rear axle vent. It’s built into the junction block on most vehicles I’ve seen.

as for the brakes. Go back to the basics, Did you bench bleed the master cylinder? I would try a pressure bleeder first. Does that have abs? To many possibilities to guess other than start over. You can measure pressures with right tools

 

Yes, master cylinder bled. There is no ABS on these brakes. 1994 year model, didn't even have airbags then. Not sure what a pressure bleeder is, but will look it up. I love the challenge and have solved countless fixes on this Jeep over the past 32 years, but this one has me stumped. I'll see what other ideas come in, but may have to take her to a brake shop of some sort and let an expert have a hand at it...can't even remember the last time I let someone else work on it...muffler replace about 20 years ago if I had to guess.

 

check your drum shoe adjustment, My 01 did the same thing when the rear drums were very under adjusted. (the PO installed the adjuster backwards on the driver side so it never self adjusted)

 

Couple thoughts..in no particular order and considering what you have already done

1) this sounds a lot like there's air in there, especially given all the parts you've replaced. Solo bleeding the way you're doing it isn't too effective. Get a mitivac or equivalent and suck it out if you're doing it solo and don't have a pressure bleeder

2. Don't get creative with how you set the push pin. Use the shop manual procedure.

3) chinesium parts are always a risk. A bad master cylinder wouldn't have to leak.

But I'm betting on air somewhere

 

My thoughts are behind the master cylinder.......the brake booster or the vacuum lines going to it. It is what gives the master cylinder its power. I have not had to change one on any of the XJ's I have owned but that is about the last thing that you have not replaced/adjusted/checked. Good Luck!

 

I just went through something very similar, I couldn't get a good brake pedal, I used a motive pressure bleeder, you have to bleed the proportioning valve at the front where the button is, with the system pressurized unscrew the fitting till you have a 1/16 plus gap, it will be a little messy, when I bled mine it literally farted the air out.

 

Thanks, hadn't heard that idea yet, will give it a shot.

 

Thanks. I did replace the booster and have put tight clamps on the vacuum hoses. But, I'll double check all that. May be time to invest in a power bleeder...the wife grew tired of helping me bleed brakes on cars years ago!

 

If you’ve bled the brakes on your other vehicles, your Cherokee is no different.
The bottle bleeding method you’re doing is very effective and works just as good as anything else does if done properly. Get someone to help you tho. Nothing against the pressure bleeders.
It was said earlier in the thread but go back to the basics.
Are the front calipers on their proper sides? They’ll bolt up on either side but won’t bleed the air unless the bleeder is at the top.

 

I spent a long time chasing a soft pedal in my track car, replacing or rebuilding most every brake part and losing my mind along the way. It ended up being a slowly failing wheel bearing causing caliper knockback.

Once you've thoroughly bled the system and verified all the brake system parts are good several times over, you need to start looking at any other system that can have an impact.

 

Thanks for all the ideas above. I tinkered on it a bit yesterday and tried bleeding the proportioning valve (which is a new part), and re-bled the master cylinder (using a kit to bench bleed it). Then bled all four corners. Nothing changed,

But, here's something I thought of today that I've not seen mentioned anywhere, so not sure it's a symptom. Today, I popped the cap off the master cylinder and started the engine and very lightly pushed the brake pedal and got a 'geyser' of fluid squirting straight up out of the reservoir. This is not normal, right? Seems all the brake pedal pressure is simply blowing back into the master cylinder (which is a new part too, but likely cheap Chinesium). I took a video of it and grabbed a screenshot of the 'geyser'. I know the master cylinder cover has a rubber gasket, but I don't think that's supposed to fully provide all the 'back pressure' the brake system needs to force the fluid down through the pipes, right? In the picture below you can see the fluid squirting up from the master cylinder. This is with just barely pressing the pedal very gently, not stomping on it.

 

Here's a link to a short video showing the 'geyser'. Again, just barely and gently pressing the pedal.

 

Did you ever set the push rod back to where it's supposed to be (aka per the shop manual)?

 

The push rod is set to engage the master cylinder just as you start pressing the pedal.