Help please 4WD and Brakes not working

Hi all,

I have a 1989 Jeep Cherokee Pioneer 5 speed that is giving me problems. My friends say that If I can find the problem then I can probably fix it with my friends help or by my self being said it is easy enough, My friends are all mechanics and are above average with Jeeps. I would just send it away to my mechanic but I want to be able to fix my own Jeep if its not to hard, Plus there wont always be a mechanic available when I go wheeling and what not. Also, should this help the Jeep was family owned first purchased by the father then sold it to his son, Its only been owned by 2 people but of the same family, I am the third owner, not family.

Here are the problems:

1. Pedal brakes are not working but the hand brake works like a charm.

2. 4WD does not work.

Let me go in depth in both problems for a bit.


1. When I was first looking at the Jeep before I bought it the previous owner said the it would need new brakes in the rear. About a month or so the Jeeps brakes were in good condition but it started to show its age and the brakes started to show signs of replacement, Or so I thought. I finally purchased new brake shoes and brake pads and I was ready to put them on. Well, When I was ready to put the new pads and shoes on I saw that both the rear and the front brakes were still at 50% and less. So, I did not replace them instead my friend suggests that it might be the Brake Power Booster. So, I have a friend who says that the Brake Power Booster is shot and another friend things that I don't have brake fluid in the Master Cylinder and another friend says that I have air in the lines and another says my brake lines are crimped somewhere or that I have a leak somewhere.

Well I don't think I have a leak somewhere because my master cylinder is full of brake fluid in fact I filled it the day we thought it was out of fluid. Also when I step on the brake pedal I do not see any puddles of brake fluid anywhere where the Jeep sits. I may have air in the line because when we took off the tires we saw that one brake caliper was missing the bleeding attachment that is used to bleed the brakes. The reason my friend says its the brake power booster is because when I press the brake pedal down it makes a loud hissing noise whenever I push the pedal either slow or fast it makes the hissing sound. One weird thing is that when we bleed on the drivers left front tire the brakes came back full force when the Jeep was off but when the Jeep was turned on I pressed the brake pedal and it did the hissing noise and it was the same as before straight to the floor. My step dad looked at the fluid in the master cylinder and said that the fluid in there looked almost a "sandy' color. Not sure what that means but I don't think that's a good sign.

So I'm at a loss as to what it could be. If it is the brake power booster how hard it is to put one in and what would I need? Maybe new brake fluid and a bucket to drain old fluid.

2. So, My 4wd does not work and I'm not sure why, I checked the vacuum lines and everything is in good working order. When I pull the lever for the 4wd it goes in to the selected mode but the "Part Time" light does not turn on. It makes a grinding noise when I move front or backward when its in 4wd mode but the front tires do not spin on their own. I have a friend who tells me that the linkage might be stretched or misaligned and because of that its not engaging correctly. If that is the case then how would I fix that?

Thanks in advance for the help.:cheers:

If the brake pedal goes all the way to the floor it usually means the master cylinder is either bad or needs to be primed. It may just be full of air.

The booster hissing may or not be a major issue. If you push the brake pedal and it takes two feet to stop the vehicle, it is likely an issue.

The rear brake wheel cylinders have a tendency to seep. Pull the dust boot off the end of the wheel cylinders, just crack the front of the wheel cylinder boot a little, if you open the back of the boot it can be a pain getting it back on again. The wheel cylinders can seep and loose very little fluid, but can suck a lot of air.

If the pedal goes almost all the way to the floor it may be a combination of bleeding and rear drum brake adjustment. If it is air, the more you pump the brake pedal the better they get. Unless the master cylinder has lost it's prime, or the seals are way bad, then you get pretty much nothing. My guess would be air in the master cylinder, without the air, you usually get either front brakes or rear brakes,, rarely do both fail. The master cylinder is a dual system, half for the fronts, half for the rears, though it isn't perfect, both can fail.

Anytime the brake master cylinder looses brake fluid or even seems over full, you have an issue. It doesn't loose fluid unless there is a leak someplace. If it seems overfull it may be an intermediate event, air farther down the system is pushing the brake fluid back to the master cylinder reservoir . The air usually eventually finds it's way to the top of the system.

There are other less likely problems, plugged proportioning valve. Maybe a rubber brake line that has a bulge where the layers have separated but not fully bust yet.

Like I said my best guess would be a brake fluid leak someplace. Brake fluid out, air in.

Next problem 4X, ratcheting sound. Do you have a shift motor? Right rear side of the front differential on the axle housing. It has vacuum lines running to it. Vacuum leak or sticky shift motor, either may give you a ratcheting sound.

Do you have the terrible Bendix ABS system? If you do, swap it out ASAP, more headaches than it is worth. have you checked/verified your t-case shift linkage is in good shape?

You said:
"when we took off the tires we saw that one brake caliper was missing the bleeding attachment that is used to bleed the brake"
That's troubling. If you mean the bleed screw then you dumped all of your brake fluid somewhere. You'll have to bleed the entire system. If there is air in the master, that can be a big difficult to get out.

8Mud said:

If the brake pedal goes all the way to the floor it usually means the master cylinder is either bad or needs to be primed. It may just be full of air.

The booster hissing may or not be a major issue. If you push the brake pedal and it takes two feet to stop the vehicle, it is likely an issue.

The rear brake wheel cylinders have a tendency to seep. Pull the dust boot off the end of the wheel cylinders, just crack the front of the wheel cylinder boot a little, if you open the back of the boot it can be a pain getting it back on again. The wheel cylinders can seep and loose very little fluid, but can suck a lot of air.

If the pedal goes almost all the way to the floor it may be a combination of bleeding and rear drum brake adjustment. If it is air, the more you pump the brake pedal the better they get. Unless the master cylinder has lost it's prime, or the seals are way bad, then you get pretty much nothing. My guess would be air in the master cylinder, without the air, you usually get either front brakes or rear brakes,, rarely do both fail. The master cylinder is a dual system, half for the fronts, half for the rears, though it isn't perfect, both can fail.

Anytime the brake master cylinder looses brake fluid or even seems over full, you have an issue. It doesn't loose fluid unless there is a leak someplace. If it seems overfull it may be an intermediate event, air farther down the system is pushing the brake fluid back to the master cylinder reservoir . The air usually eventually finds it's way to the top of the system.

There are other less likely problems, plugged proportioning valve. Maybe a rubber brake line that has a bulge where the layers have separated but not fully bust yet.

Like I said my best guess would be a brake fluid leak someplace. Brake fluid out, air in.

Click to expand...

The brake pedal does go all the way to the floor but the hissing sound comes from the inside when I push on the brake pedal. If the master cylinder is bad then how would I go in fixing it or if it is full of air how would I purge the system? I'm guessing bleed the brakes? Also how would I prime the master cylinder? And what is priming? I'm such a noob and I'm sorry that I'm inexperienced.

I don't think that there is air in the system because as you said "the more you push on the pedal the better it gets". Well when I push on the pedal it does not get any better it just stays the same. What is a proportioning valve and where can I find it to look at it and diagnose the problem.

8Mud said:

Next problem 4X, ratcheting sound. Do you have a shift motor? Right rear side of the front differential on the axle housing. It has vacuum lines running to it. Vacuum leak or sticky shift motor, either may give you a ratcheting sound.

Click to expand...

If by shift motor you mean a 5 speed then yes, If not then I do not know what a shift motor is.

Johnnie Walker said:

Do you have the terrible Bendix ABS system? If you do, swap it out ASAP, more headaches than it is worth. have you checked/verified your t-case shift linkage is in good shape?

Click to expand...

I'm actually not sure if I have the Bendix ABS system, How would I find out if I had it short of asking a mechanic look at it and tell me?

The shift linkage underneath the Jeep? I have not looked at it, but tomorrow I look at it in the morning.

jworth said:

You said:
"when we took off the tires we saw that one brake caliper was missing the bleeding attachment that is used to bleed the brake"
That's troubling. If you mean the bleed screw then you dumped all of your brake fluid somewhere. You'll have to bleed the entire system. If there is air in the master, that can be a big difficult to get out.

Click to expand...

Yes, The bleed screw is missing but I have a full master cylinder full of brake fluid. Should there be air in the master cylinder how would I purge it?

Restruction said:

The brake pedal does go all the way to the floor but the hissing sound comes from the inside when I push on the brake pedal. If the master cylinder is bad then how would I go in fixing it or if it is full of air how would I purge the system? I'm guessing bleed the brakes? Also how would I prime the master cylinder? And what is priming? I'm such a noob and I'm sorry that I'm inexperienced.

I don't think that there is air in the system because as you said "the more you push on the pedal the better it gets". Well when I push on the pedal it does not get any better it just stays the same. What is a proportioning valve and where can I find it to look at it and diagnose the problem.



If by shift motor you mean a 5 speed then yes, If not then I do not know what a shift motor is.



I'm actually not sure if I have the Bendix ABS system, How would I find out if I had it short of asking a mechanic look at it and tell me?

The shift linkage underneath the Jeep? I have not looked at it, but tomorrow I look at it in the morning.



Yes, The bleed screw is missing but I have a full master cylinder full of brake fluid. Should there be air in the master cylinder how would I purge it?

Click to expand...

Unless it was swapped, you have a the vac-disco D30 axle. Check to see if the vac lines/connector is connected to the axle properly, that can be part of the issue, as the light is also controlled by this.
IIRC, the bendix system did not have a booster for the brakes?

The booster on my 87 hissed for years, it never got any worse and stopping the Jeep didn't require any extra pedal effort. If the brake booster is the/a issue, the force require (how hard you have to push the pedal) to stop the Jeep increases.

First thing I'd do is an inspection of the brake system, there may be multiple problems. Take a flashlight and follow every brake line front to rear, look for stains from brake fluid. Check the rear wheel brake cylinders.

Make a list of what you find, then take it to a mechanic. From the sound of things, you may get in over your head, trying to do it yourself. Brakes can turn into a pain, the parts rust and seize, the fittings, if you have to replace something, can turn into a nightmare even for a good mechanic.

Two things you have to have is good brakes and tires, most everything else is optional.

Brake fluid can remove paint, be careful with that stuff, you can wash it off with soap and water pretty well.

The only real way to get un-NOOB-ed is to watch how somebody else does it and research. There really is no substitute for crawling around under your Jeep. I've likely spent more time under my Jeep than I have on my wife.

I used to have a Gremlin, hit the brakes one day and went right through an intersection. Old style single stage master cylinder, the Jeep master cylinder really shouldn't do that, it is dual stage. That is what makes me think it may be full of air. But seriously if you don't trust it, have somebody swap it out. Change out the front brake caliper at the same time, it's doubtful you'll ever get that broken bleeder valve out of there.

The front axle shift motor or front axle disconnect, is located on the back side of the right axle housing. Block the tries, crawl in behind the right front tire and look towards the front of the Jeep at the backside of the axle housing. I always take a flashlight, the extra light tends to show up flaws you may normally miss.

First thing to check is if any of the vacuum lines got torn out, I've done it. A stick gets wedged in there and tears out the vacuum lines.

You can take the vacuum lines off of the shift motor, carefully, they get brittle. Spray some oil into the vacuum openings, it's in the book and really seems to help.

Next go to the front of the vehicle and look behind the front bumper, right side (right as you are sitting in the drivers seat), There is a black vacuum canister in there. Make sure it hasn't fallen off and the vacuum lines are still connected. The larger line runs under the battery box, it tends to rot in this spot.

Not enough vacuum and the shift motor or front axle disconnect, whatever you wish to call it, isn't going to work right. What the front axle disconnect does is slide the right front axle out of the differential (basically) and allows the front differential to free wheel. Newer XJ's don't have a shift motor. If it's there, it has to work, or no 4X.

There are also vac lines to the transfer case, these are for the dash indicators for 4hi, 4lo. The plastic vac lines get brittle, you can splice them with rubber hose.