1989 brake problem

Hi all,

I finally saved up enough money for my XJ to buy it a brand new brake booster. I confidently went into autozone today to purchase a new brake power booster but when I asked the cleric he asked if I had ABS I don't think I do at least I think. But I said no and continued to look at the brake power booster without ABS. Someone once mentioned that I may have whats called the Bendix ABS system but I'm not sure if I have it. How would I check to make sure if I have it?

Another product caught my eye as we were looking on the computer for the Brake Power Booster and it was the Brake Power Booster with the Master Cylinder, That got me thinking if I should go ahead and bite the bullet and just order that and receive it 4 days later.

Here is the symptom that my friends and I have come across:

1. Pedal goes straight to the floor with no pressure or resistance.

2. Makes a hissing noise when pressed.

3. Master Cylinder is full with no signs of leaks.

Now would I have to replace the master cylinder if I just get the Brake Power Booster? I've been told that the master cylinder may be full of air how would I purge the system? I've also been told to prime the master cylinder how would I go about that?

Also, how would I go about replacing the Brake Power Booster on my 1989 Cherokee Pioneer 5 speed is there a diagram on how to do so? On a level of 1 to 10, 10 being the hardest how hard would it be to do it alone / an inexperienced mechanic (me) to do? Or is it something I should have one of my friends (who are somewhat mechanics) help me do it? Also, I am so inexperienced that I don't even know how to bleed brakes so perhaps a write up..(sorry).

Is it hard to replace a Master Cylinder if its bad? Diagrams / write up? How would one purge a master cylinder of air and how would one prime it?

I plan to do the Brake Power Booster tomorrow should the weather permit and if the part comes in, or I could wait for the Brake Power Booster and Master Cylinder combo to come in.

Thanks in advance.

There's no vacuum assist on the ABS. There's a pressure modulator right next to the master cyl. So if you see a whole lot of brake lines and no big black "drum" bolted to the firewall, you have ABS. Otherwise you don't. You can also look for the presence of the sensors ar the wheel hubs.

Assuming it's non-ABS, I would submit you have not diagnose the problem enough to determine the booster's bad. What happens if you pump the pedal? Do it with the engine off and on.

I would also suggest you do NOT mess with it alone. Improperly serviced brakes are a danger to you and everything and everyone around you.

Saudade said:

There's no vacuum assist on the ABS. There's a pressure modulator right next to the master cyl. So if you see a whole lot of brake lines and no big black "drum" bolted to the firewall, you have ABS. Otherwise you don't. You can also look for the presence of the sensors ar the wheel hubs.

Assuming it's non-ABS, I would submit you have not diagnose the problem enough to determine the booster's bad. What happens if you pump the pedal? Do it with the engine off and on.

I would also suggest you do NOT mess with it alone. Improperly serviced brakes are a danger to you and everything and everyone around you.

Click to expand...

this.

Bribe a mechanic friend with some beer to come over and diagnose them for you, and show you how the system works before you go mucking with it.

From your description I would say that your master cylinder has probably failed, but without knowing when/if the pedal gets hard, and if your brakes work and if the master is pushing fluid it's impossible to tell you.

If the brakes were working, and suddenly failed, it sounds like the MC (Master Cylinder) and the Vacuum Booster (VB), are both bad. I have learned the hard way with jeeps to only use a brand new steel housing MC, do not get a rebuilt, and do not get aluminum, they do not hold up. They leak out the rear later and kill the vacuum boosters!!!!!

I never replace a VB with a brand new steel MC now!!!!

The work is not very hard if you do not have ABS. There are plenty of great visual aids and books, instructions that come with the MC, for instance of bleeding the MC.

When you do the job, save some grief later and install a new brake light switch, about $12 more, goes on the peddle end that attaches to the MC.

Google you tube for how to videos on the brake work.

Check each wheel (inside the rear drums, check the brake lines and fittings, and check around the front rotors and calipers) for any brake fluid leak signs just to be sure, but if the MC is full, and you have absolutely no pressure when you pump, pump, pump the peoties out of the peddle, the MC is most likely toast.

Did you just get this jeep, or were the brakes working and suddenly failed with the MC still full of fluid?

The OP said:

Makes a hissing noise when pressed.

That implies it has the vacuum booster, and that it leaks!!! Or in other words, it sucks, LOL!:laugh3:

Oh, and don't buy the cheap beer, take good care of the mechanic friend, LOL!

Saudade said:

There's no vacuum assist on the ABS. There's a pressure modulator right next to the master cyl. So if you see a whole lot of brake lines and no big black "drum" bolted to the firewall, you have ABS. Otherwise you don't. You can also look for the presence of the sensors ar the wheel hubs.

Assuming it's non-ABS, I would submit you have not diagnose the problem enough to determine the booster's bad. What happens if you pump the pedal? Do it with the engine off and on.

I would also suggest you do NOT mess with it alone. Improperly serviced brakes are a danger to you and everything and everyone around you.

Click to expand...

I don't think that I have abs because I have a brake booster (big black drum) that is bolted to the fire wall.

When I pump the pedal with the engine off or on it just does a hissing noise and no pressure builds at all.

I have replaced the brake power booster with the help of my friends who are somewhat mechanics (ie my friend works for a mechanic and is an apprentice.

87manche said:

this.

Bribe a mechanic friend with some beer to come over and diagnose them for you, and show you how the system works before you go mucking with it.

From your description I would say that your master cylinder has probably failed, but without knowing when/if the pedal gets hard, and if your brakes work and if the master is pushing fluid it's impossible to tell you.

Click to expand...

I cannot have beer in my household because my stepfather is a recovering alcoholic. I do believe now that I need a new MC because I replaced the brake power booster in my jeep. I have pressure now but the brakes still don't work, And now my brake lights come on when I press the pedal but they don't go off now or sometimes they don't come on at all.

Ecomike said:

If the brakes were working, and suddenly failed, it sounds like the MC (Master Cylinder) and the Vacuum Booster (VB), are both bad. I have learned the hard way with jeeps to only use a brand new steel housing MC, do not get a rebuilt, and do not get aluminum, they do not hold up. They leak out the rear later and kill the vacuum boosters!!!!!

I never replace a VB with a brand new steel MC now!!!!

The work is not very hard if you do not have ABS. There are plenty of great visual aids and books, instructions that come with the MC, for instance of bleeding the MC.

When you do the job, save some grief later and install a new brake light switch, about $12 more, goes on the peddle end that attaches to the MC.

Google you tube for how to videos on the brake work.

Check each wheel (inside the rear drums, check the brake lines and fittings, and check around the front rotors and calipers) for any brake fluid leak signs just to be sure, but if the MC is full, and you have absolutely no pressure when you pump, pump, pump the peoties out of the peddle, the MC is most likely toast.

Did you just get this jeep, or were the brakes working and suddenly failed with the MC still full of fluid?

Click to expand...

I got this jeep back in December of 2011 but it has been sitting for a couple of months, And yes the brakes were working but over time it kept getting harder and harder to brake. Also, the MC is full of fluid but its not the correct color, as my Step dad told me it looks sandy.

Ecomike said:

The OP said:

Makes a hissing noise when pressed.

That implies it has the vacuum booster, and that it leaks!!! Or in other words, it sucks, LOL!:laugh3:

Oh, and don't buy the cheap beer, take good care of the mechanic friend, LOL!

Click to expand...

I have replaced the brake power booster but there are no leaks that I can see.

I replaced the brake power booster and I have regained pressure in the brake pedal but now there are new symptoms in my jeep.

1. Brake pedal has pressure but the brakes still don't work.

2. The brake light comes on and stays on sometimes when I press the brake pedal sometimes it does not go off it just stays on.

I'm lost as what to do now please help me.

Note from DJ
In your post on 3-19-2012 titled Help please 4WD and Brakes not working
http://www.naxja.org/forum/showthread.php?t=1084452

Now in your original post under the sub title

Brakes:
You stated the following information.

QUOTE:
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”.

My question to you is when you “filled it the day we thought it was out of fluid” was either of the two brake fluid reservoirs in the master cylinder empty of fluid, or just a little low on fluid and if low only, how low?

Don’t worry about the brake light problem for now, that is a easy fix and has nothing to do with your brakes not working properly.

Restruction said:

I have replaced the brake power booster but there are no leaks that I can see.

Click to expand...

It only takes a little bit of brake fluid leaking out the back side of the MC, into the Vacuum booster, to destroy the rubber diaphragm seal in the Vacuum booster, and near as I can tell the brake fluid ends up going into the vacuum line to the engine as a gas over time, evaporates under a vacuum, so no visible fluid leak is ever seen, just low fluid in the MC. My only clue was a brand new Vacuum booster failed in just 2-3 months, and there was a trace of brake fluid on the rear inner area where the MC attaches the VB. The VB was rebuilt, and less than a year old!

There is another valve, accumulator valve inline between the slave cylinders at the brakes and the MC, that can be having problems, especially trapped air!!! Which is very hard to bleed out!!!