Issues w/ the brakes - possibly booster??

Well I just bought this Jeep last week and the previous owner told me that the brake booster was bad. Before I even picked the Jeep up, I found one on Ebay and bought it (only $26 shipped). Anyway, I have the Jeep now and it looks like the booster I bought won't work. I guess my XJ has ABS (which I didn't even think to ask nor did I know that the boosters wouldn't be the same - my Chilton's guide didn't mention different instructions for ABS or non-ABS equipped vehicles). The booster I got has a master cylinder bolted directly to it whereas my fluid resevoir is a plastic container (opposed to the metal type that I usually associate w/ as master cylinders).

So, does my Jeep indeed have ABS and does it still even have a brake booster? I only get about 1/2 pedal travel and it's very hard to push, but the brakes barely work. When I tried the test suggested in Chiltons - to pump brake while vehicle is off, then put steady pressure on pedal, start vehicle and pedal should go to floor - mine doesn't do that - the pedal stays the same. Thanks for any help.

Tried to edit and evidentally there is a rule against that if posted longer than 45min. ago.

Anyway, I've determined that I do have ABS (also have a Haynes guide which has better pictures) and it shows that ABS still has a booster and also a booster pump, but neither look anything like what I have bought, so I guess that's a $26 learning mistake. Haynes also only has one set of booster replacement instructions, so if it indeed is my booster, I don't even have instructions on how to replace!! I'm sure it's just unbolting / rebolting, but it definetely looks like a PITA opposed to non-ABS vehicles. Is there anything else I should look into besides the booster? Where is this pump?

What year is your Jeep? Keep in mind that '95 and up used the newer style master cylinder (ABS or not), and '94 and down had the all metal unit. If you look through old posts, you'll find that the '95 and up unit is the more sought-
after, and many go through the trouble to adapt the newer cylinder to their older rides. new boosters are not too terribly expensive, and boneyards often have a few to choose from.

You may want to call the dealer, the older ABS system was quite problematic, last I knew there was a standing recall on a lot of parts.

Sorry, it's a '91. When I pop the hood and look at the top right corner, I see a plastic containter next to the windshield wiper fluid resevoir. It's a brake fluid container and I don't see the more traditional master cylinder. Is that under this? The plastic container is on a metal "rail" that has several pipes runnign out of it going into the proportaining (sp?) valve, etc. Also, where is the booster pump located? According to the Haynes drawing, the "rail" is the booster and then there is also a seperate "booster pump". The guy I bought the booster from though stated that it would fit all 84-96 XJ (here is a link to another he's selling - http://cgi.ebay.com/ebaymotors/JEEP-CHEROKEE-BRAKE-BOOSTER_W0QQcmdZViewItemQQcategoryZ6763QQitemZ8064295733QQrdZ1QQsspagenameZWDVW )

I stumbled across a link on this site that was on DC's site where you could type in you VIN and it would tell you any unfulled recalls - the only one I had was the switch when you're in park (which mine is bad or needs to be adjusted b/c I have to start it in N). I guess it couldn't hurt to have them check it out...

I'm not sure exactly when the boosters changed, but they did change to a more powerful unit, and I'm pretty sure the one shown is the earlier type. I know my 87 and 89 had the old style with metal fluid reservoir, and the 95 has the new, with a double diaphragm vacuum reservoir and a plastic fluid reservoir. If memory serves, the 93 had the new type too but I don't have one here any more to check, so I might be wrong about that. Anyway, the newer style is a definite improvement. If you have non-working ABS it might be worthwhile researching a way to disable it and put in a non-ABS booster, but the one in that ebay link doesn't look like a good candidate. I have not searched here, but you might try searching for subjects such as booster conversion or booster upgrade, because some people have done the upgrade with success.

gone postal said:

The plastic container is on a metal "rail" that has several pipes runnign out of it going into the proportaining (sp?) valve, etc. Also, where is the booster pump located?

Click to expand...

The "rail" is the master cylinder. The big bell shaped thing is the "booster" which is really just a giant vacumn diaphram that helps pull on the master cylinder rod. ABS adds a set of valves to release pressure from the brakes to prevent a lockup. It also adds a hydraulic pump to add pressure in and keep the brake pedal from sinking to the floor.


On the starting in P problem, do a google on "Jeep NSS Clean" and you'll get a few good writeups on cleaning the switch. It's a relatively easy job and save you from buying a $300 switch.

lawsoncl said:

The "rail" is the master cylinder. The big bell shaped thing is the "booster" which is really just a giant vacumn diaphram that helps pull on the master cylinder rod. ABS adds a set of valves to release pressure from the brakes to prevent a lockup. It also adds a hydraulic pump to add pressure in and keep the brake pedal from sinking to the floor.


On the starting in P problem, do a google on "Jeep NSS Clean" and you'll get a few good writeups on cleaning the switch. It's a relatively easy job and save you from buying a $300 switch.

Click to expand...

Thanks - this clears things up some. So, where is my booster located then? It looks like the master cylinder (rail) connects right to the firewall - I don't see anything that resembles a brake booster like I posted in the link above. (of course I'd remove the master cylinder from the donor booster - I know that all I need is the bell shaped piece). Also, it is safe to say that the booster I bought isn't compatable w/ my system then? How do I know for sure if I have ABS? I'm assuming I do based off of a drawing in the Haynes, but I don't have a build sheet or anything vehicle specific for this Jeep yet.

As for the switch - thanks - don't worry though, I had no intention of spending $300 on another one - that's half the cost of the vehicle!!!

I guess the question should be - do you have power brakes.

Have you tried replacing the check valve on the master cylinder. It's like a $10 part. I had a problem with my brakes where I had to stand on the brake pedal to get the jeep to stop. The pedal would move only slightly and was like stepping on a rock. I replaced the check valve and the brakes now work perfectly. It may be an inexpensive test to verify if you really need to do all that work. Just pull the littel hose off and pull the check valve straight off and push the new on straight on, reconnect the little hose and done. Took me all of 30 seconds to do. Simple as that.

Sorry that this is so difficult - totally new vehicle to me. I found some more info and yes, I do have ABS, so yes, I also have power brakes. I now know that the metal "rail" under the resevoir is my master cylinder / brake booster. This gets it's "boost" from a booster pump which is located on the other side of the engine bay. Here is a pic of my system just in case there is any confusion...




So, now that I know I definetely have ABS & power brakes - what could case my pedal to only go down about half way and be rock hard, but barely stop the vehicle? I assume the brake booster, but I guess it could also be the booster pump, any of the various vavles, etc?

Matt_S - Your brakes sound exactly like mine, but I think we have different systems. I believe the check valve is a vacuum system component whereas my system is completely hydraulic. This is probably going to be a nightmare to fix....

I would start with a good bleed of the whole brake system, which should be done anyways if the vehicle is new to you, and see where that leaves you. That may solve the issue and will only cost you a few bucks in brake fluid

Maybe not related, but some info anyhoo:

There are 2 indicator lights used with anti-lock brake systems. One light is red the other one is yellow. Both are in the instrument panel. The lights are in the circuit with the self diagnostic program in the ECU and signal both normal & system faults.
The yellow light indicates anti-lock system condition. It is in the circuit with the modulator solenoids & relay. The light goes on at start up & goes out when the self diagnostic program determines that the system operation is normal. Do you have a yellow light that does this? Or has the bulb been removed?
If there is a fault the yellow light remains on until the fault is corrected, the battery is disconnected or the ignition switch is cycled {turned off, then on} Cycling the ign. switch may not turn the light off after some faults. Whenn the yellow light is on {system is faulted} the solenoids are disabled.
The red light serves as the system warning light[low fluid, parking brake on, system pressure differential, etc] The light illumintes in tandem with the yellow one when certain faults occur.
There are time delays built into the indicator lights & are provided as a means of identification of some faults.

"....what could case my pedal to only go down about half way and be rock hard, but barely stop the vehicle? I assume the brake booster, ......"

had exact same symptoms on my 98. replaced booster and all is peachy.

I just went thru all of this over a 5 day period last week. (91 Cherokee Limited.) Started out with a Check Antilock light, followed by a brake light, and a hard pedal. Got on this here site, and 5 days and $200.00 later I had a upgraded 95 dual diapraghm(sp?) system, and new rear cylinders. Way better brakes, and I have not even replaced the pads/shoes yet!

I say if you can do the job, Reflare brake lines etc.... Go for it. Im glad I did.
The ABS system in these earlier XJ's suck.

The ABS light doesn't come on - possibly blown/removed bulb, etc. The red brake light is constantly on. I couldn't care less about ABS - this is intended for a trail / beach rig, but I would at least like to have power brakes - especially when I get ready to lift it and put on larger tires. I guess it's off to hunt down a new booster. Anyone done the job before? Just wondering how long it should take and if there are any special tricks that would be helpful to know beforehand. Also, where is a good place to find parts? The local junk yards are always way higher than what I see people quote on this site and even w/ the booster I bought I got it for $26 shipped (10 for the booster itself) whereas the local wanted $50.

go here and put in the vin number to see if the ABS needs recall work, or pull it all and go with standard brackes




http://www-5.jeep.com/webselfservic...recall&country=us&emailUrl=goToEmailForm('R')

I'd like to retract the ABS light info - I assumed the ABS light would be next to the regular brake light, but looks like I was wrong. My ABS light is in the bottom slot of warning lights and there was a piece of electrical tape over it. The light does come on and it stays on. So, now I have a continous brake & ABS light....not good....

I have the same year xj and same problem. Only the ABS warning light went out like a month ago. It stayed on for like 6 months.... There is a factory recall on the pump motor and some other parts. I made an appointment to get it fixed, took it down there, and it has already been done. Lamn! so they wanted to charge me....HEll no i will switch to normal brakes!