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Brake booster upgrade.


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My 88 Comanche I did the 95/96 power booster upgrade. Well after a couple of years the booster is leaking down vacuum. I just acquired a 97 Cherokee rolling body that still

Has the master cylinder and power booster. Will that one bolt up like the 995/96?

 

 

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The bolt pattern is the same as that 95/96 booster. They were the same bolt pattern on XJ’s from 91-01. All 91+ boosters will require some slight mods to the brake pedal connection so your pre 91 brake light switch will work properly. Make sure to hold onto the little aluminum 1/4” spacer that’s behind your booster if you still have it. It will provide the spacing needed for the 97+ booster to clear the pinch seam on the firewall. I run an 01 booster and MC on my 91 MJ. Was a bolt on for me since i have the newer style brake light switch. 
 

However, before you go that route, could it be that you just need to replace the check valve in your existing booster?

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LOL!! Who did that?
 
Even after that, I'll still gladly share the switch that does it all. Cadillac part I think.
 
 
1541765439_Brakelightswitchbooster.jpg.ab841411d33f783e62ca0436ca16a21b.jpg
1270696933_Brakeswitch.jpg.7e99a16f632a0803f0730a1b7d373854.jpg

Thanks cruiser54 on the tip. That brake switch looks like what I used on my 87 XJ 15 years ago. I did the rod modification on my 88 MJ. I sold my 87 XJ 12 years and have forgotten most of everything


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You can also use the contact switch from a later model XJ as well.  Same concept.

 

There are 6 wires coming from the switch, you only need the two for the light circuit.  They are pink/red and white, IIRC.

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1 minute ago, mjeff87 said:

You can also use the contact switch from a later model XJ as well.  Same concept.

 

There are 6 wires coming from the switch, you only need the two for the light circuit.  They are pink/red and white, IIRC.

But you need 4 wires on an auto trans vehicle. 2 for the brake light switch which make contact when the pedal is depressed and 2 to break the contact for power to the torque converter. 

If that switch works, it would be great to know the wiring colors. 

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I did the WJ booster in mine, and after messing with grinding the rod for the brake switch and failing, I cut the end off of my original and the WJ and welded my original end to the WJ rod. I also used this opportunity to shorten it slightly to the correct length. Its been working great for years now. Ill have to remember this trick for next time though!

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12 hours ago, cruiser54 said:

Correct. Remove the white plastic switch and use the Caddy one in it's place. 

 

On another note, the 99 to 2004 Grand Cherokee booster/master is my favorite swap,

Cruiser…any advantage to your favorite swap over the classic 95-96 XJ booster/MC?

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Yes. I've done both. 

First off, availability.

Secondly, the WJ booster installs more easily since its mounting studs are small and you don't have to fight it going in.

Thirdly, doing the brake lines is easier because you have the flexible lines from the master. Just cut off the hard line, install the fittings from your old lines and put a double flare on the pipe.

Fourthly, you don't have to move the washer bottle.

the only thing you have to do other than brake light switch and drilling the booster rod is making a little clearance at the body seam. I'll include photos.

 

I noticed that the braking was also stronger with the WJ set-up.

 

 

Booster clearance WJ.jpg

Booster Clearance.jpg

Booster firewall cut.jpg

Booster firewall.jpg

Booster piping.jpg

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14 hours ago, cruiser54 said:

Correct. Remove the white plastic switch and use the Caddy one in it's place. 

 

On another note, the 99 to 2004 Grand Cherokee booster/master is my favorite swap,


Is there any other rewiring, or is it just remove OE switch -> install OE wires to the correct spot on caddy switch -> install caddy switch to contact brake pedal?  I am an electrical dumbass, so that would be helpful here as well

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6 hours ago, cruiser54 said:

Yep. Make sure you install/adjust the switch properly so it doesn't get impacted by the pedal and just operates the switch. 


Well snap, thanks for that!  I have a WJbooster/master/lines that I havent installed because of the grinding.  Since its that easy, DD booster here I come!

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18 hours ago, cruiser54 said:

Yes. I've done both. 

First off, availability.

Secondly, the WJ booster installs more easily since its mounting studs are small and you don't have to fight it going in.

Thirdly, doing the brake lines is easier because you have the flexible lines from the master. Just cut off the hard line, install the fittings from your old lines and put a double flare on the pipe.

Fourthly, you don't have to move the washer bottle.

the only thing you have to do other than brake light switch and drilling the booster rod is making a little clearance at the body seam. I'll include photos.

 

I noticed that the braking was also stronger with the WJ set-up.

 

 

That makes sense, if you are not starting over, like I did.  When you rip out all of old junky parts, doing it from scratch with '96 parts isn't that tough.  (and besides, I SO much enjoy flaring brake tubing):mad:

 

 

 

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  • 1 month later...
On 11/5/2021 at 7:31 PM, RustyRodder said:


Is there any other rewiring, or is it just remove OE switch -> install OE wires to the correct spot on caddy switch -> install caddy switch to contact brake pedal?  I am an electrical dumbass, so that would be helpful here as well

 

Just did this today, here's a pic to help. 

20211211_161110.jpg

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On 11/4/2021 at 10:24 PM, cruiser54 said:

LOL!! Who did that?

 

 

wow, not sure how I missed this topic but that's an old auto-correct that Rob put in years ago for the kids saying "w.a.t" instead of "what".  :laugh:

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