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Brake issue! !!

P

pezman65

NAXJA Forum User
Location
san diego
Hey everybody I'm stumped my 91 XJ intermittently gets a soft pedal, but I'm not losing any fluids .so I'm thinking that the master cylinder o-rings are worn. When I start my engine and I backup the pedal goes all the way to the floor then I pump it a couple times and it gets hard and driving down the road it's usually pretty good and then when I stop and I go to take off its soft again all the way to the floor until I pump it .
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I'm not sure what it is but I went to O'Reilly's and my buddy is a manager there and we could not find this master cylinder on the Internet or in his computer for parts any help would be great! I'm putting pics on here if anybody knows what this master cylinder is or where I could get it would be very grateful thank you!

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Definitely sounds like a master cylinder. Was that originally a diesel or something? Haven't seen that type before in an xj.
 
Isn't that the abs Cherokee brake system? Wasn't there some sort of lifetime guarantee jeep was forced to issue because it was so bad?


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What model have you seen this on before Overland? I can't find it anywhere why would it be on my 91 Limited? WTF!

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Yeah it's definitely the Bendix 9 I'm going to find out about the warranty that be awesome if they covered it thanks

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If anyone here knows about the work and give me a shout thanks much for all the help. Also if I can't get this fixed what would I change this out from?

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Check this link out
http://www.allpar.com/fix/ABS.html
I'd call the 800 number and talk to jeep .

I don't know much about the jeep abs, some of the guys here can probably steer right.

From what I was reading it's a one piece deal, so there will not be the parts for it rebuilt available at auto zone .

You might be able to convert to regular none abs , but that might be fiddley to get right.




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So people say Chrysler refused to fix it others had better luck. From Chryslers pov is 2 grand in parts and labor worth more than the vehicle.


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pezman65 said:
What model have you seen this on before Overland? I can't find it anywhere why would it be on my 91 Limited? WTF
Click to expand...

I have it on a 90 Laredo. I plan on just swapping a regular system in place of it when that project comes around.

I understand that parts of the system are under high pressure and are dangerous to disassemble.
 
Ok, I also have the '91 with ABS. I have that same set up. Or should I say had. Anyway, I went through the same thing. There is a factory lifetime recall and repair. In my experience, it worked pretty good when it worked. The problem is there is a high pressure pump that sends pressurized brake fluid to an accumulator and ,as far as I know,this is only what the recall/repair covers, the pump. The pump itself wears out every couple of years. The dealers don't like that but they have no choice but to honor the repair.

Now, with that being said, your problem is not the pump. It most likely is the master cylinder. I have done a conversion on my XJ so I have all the ABS stuff laying around. All of it worked good when I pulled it out except the pump started acting funny so I pulled it all. You are more than welcome to it.

Let me know.
 
Last edited:
Overland said:
I have it on a 90 Laredo. I plan on just swapping a regular system in place of it when that project comes around.

I understand that parts of the system are under high pressure and are dangerous to disassemble.
Click to expand...

The only thing under pressure is the accumulator (the black bulb looking thing next to the master cylinder). As long as you don't disassemble that, you'll be fine.
 
Kind of a crazy set up really. Instead of a vacuum actuated booster it uses pressurized brake fluid that, through a valve, is shot into the master cylinder behind the master cylinder's cylinders for the power assist.
 
That..... Is.. Incredibly dumb lol never seen that and im sorry you have to deal with early 90s crap. This looks like it was designed by the same guy who designed fords early 90s TBI. I vote to add a vacuum reservoir and put a booster in. I dont know if its possible on these but id sure as hell try my hardest

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So I talked to the dealer and they said they won't even take my vehicle in to fix anything that there are no parts for it so then I talk to Chrysler and they say that they won't do anything either so I asked him so I'm basically just totally screwed! So what if I have to go to the junkyard and pull a brake system what would I be looking for and how hard is? this I'm kind of mechanically inclined but I'm no fabricator. If anybody has a link to a form that shows you how to do this feel free to send it to me thanks much!

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If it was a diesel in a prior life and swapped for a gas 4.0, the diesels do not have enough vacuum to operate a typical vacuum operated booster brake MC/brake booster system, and so they have to do something else to supply the boost pressure. My 85 XJ with the Nissan SD22 diesel transplant has a rotary vacuum pump on the extended shaft on the back side of the alternator. That makes alternator work special fun for me.

So if it was diesel that could explain the odd brake system. Did they still make any diesels in that year? What does that emission tag on the drivers side firewall above the MC say was originally in there?
 
Ecomike said:
If it was a diesel in a prior life and swapped for a gas 4.0, the diesels do not have enough vacuum to operate a typical vacuum operated booster brake MC/brake booster system, and so they have to do something else to supply the boost pressure. My 85 XJ with the Nissan SD22 diesel transplant has a rotary vacuum pump on the extended shaft on the back side of the alternator. That makes alternator work special fun for me.

So if it was diesel that could explain the odd brake system. Did they still make any diesels in that year? What does that emission tag on the drivers side firewall above the MC say was originally in there?
Click to expand...

Nah, he just has the normal 1991 ABS system. I had the same thing.
 
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