Grand Cherokee Master Cylinder and Brake Booster Swap

[scoobyxj]

So you have swapped the booster and now your brake lights stay on all the time?

Sounds like you didnt take enough material off the end of the booster rod and now its putting constant pressure on the brake light switch.

Not sure about earlier models but on my 99 you can adjust the brake switch. Quarter turn counter clockwise to remove it and then pull the plunger out. Reinstall, and pull back on the brake pedal to set it correctly.

 

[Talyn]

My old 91 was the same way as is my 2000. The switch is adjustable.

 

[XJLI]

Why would my brake lights stay on all the time? Ive got an 88 I am in the process of doing this mod on.

My 93 did this. Idk why, but it stopped fine.

 

[Muad'Dib]

Not sure about earlier models but on my 99 you can adjust the brake switch. Quarter turn counter clockwise to remove it and then pull the plunger out. Reinstall, and pull back on the brake pedal to set it correctly.

87-90 is not adjustable.

 

[lawsoncl]

87-90 is not adjustable.

Rock Auto has the whole switch for $3.75 plus shipping. Local auto store probably still be under $10. It might just need cleaned. There really isn't much to them, but at that price I'd just replace it. Make sure you note the order the washers went on when you remove it.

 

[stefanoquinto]

I'm finishing the installation of the wj's brakes on my '90 xj (abs bendix).
now I have to flaring pipes.
can someone show the pic of right flaring tool?
thanks

 

[SonicCougar99]

Bumping this back up as I am looking into this. My brakes in my 89 are terrible, and the booster might be bad (vacuum noise when I press on the brakes partially). I live in a fairly remote area where junkyards are a bit of a journey for me, so I really need to know everything I need in one trip to the j/y. From what I'm reading, I need a WJ MC/booster and some brake line. Is that all I would need to pull from the yard? Or are there other pieces that would make the swap easier? I have very limited free time with working two jobs, and my XJ is my DD, so I need to be all done in one day. Thanks.

 

[2stix]

if you have access to wj stuff thats good. but what i did was use the duel diaphram booster and master from a 95/96 XJ. since i had the bendix antilock system i also needed to replace the entire pedal assembly, so i grabbed that too from the junk yard. not sure if your pedal assembly will work with the WJ stuff so you will need to research that. i used all the stuff from the 95 doner and it all bolted right in. no cutting, bending, fabricating of any sort except making a few new hard brake lines. i also used my old proportioning valve since the doner one had a small nick and was leaking. all worked perfect. just make sure you get the small hard brake lines from the master and proportioning valve as they are hard to make with those short small bends.

 

[SonicCougar99]

My 89 doesn't have ABS, so from what I've read, that makes things slightly less complicated. I just want to make sure I get everything I need in one shot, because I don't really have the ability to be running back and forth to parts stores or back to the j/y in case I miss something the first time around.

 

[BulletMaker]

I'm personally doing the ABS conversion, and found this on a 1990 XJ same model as mine (even had the ABS) but the abs went bad and they did this mod to it.

You probably don't need the proportioning valve, but you need the booster, the master cylinder, I grabbed the proportioning valve, as it was attached to the same assembly (and needed it anyways). There's also a big vacuum tube that connects the booster to a hose fitting just above the EGR valve.

Also, you may need to dig around the yard quite a bit, a lot of the grand cherokees have ABS brakes on them, you can tell because there's a big ABS pump sitting right in front of the booster/MC assembly.

 

[SonicCougar99]

Just to make sure I have this right, I need to find a non-ABS WJ for the swap? Does it matter I6 or V8?

 

[Talyn]

I need to find a non-ABS WJ for the swap?

Good luck. There is no such thing.

 

[Tacedaddy]

all of them are the same.. I6 or V8 and yes they all have abs.. make sure you grab the lines that go from the master to the ABS unit. that will make your life much easier

 

[SonicCougar99]

Got it, thanks. Didn't know that the ABS was standard on the WJ's. Ah, to live the life of constantly having old(er) cars where things like "ABS", "Power Steering", and "Air Conditioning" were optional items lol.

 

[89Mock]

Very old bump because the information is relevant...and old stuff is the best stuff.

Has anyone experienced cruise control no working properly after swapping the WJ booster into an older XJ? I just did my swap and cruise control works until I hit the breaks. It doesn’t cancel. It speeds right back up no matter how much I seem to slow down. Can anyone come up with an idea why the cruise control would start back up after doing the swap?

 

[kastein]

Do your brake lights work? If not, you may have not mounted or wired the brake light switch right and the ECU only knows you hit the brakes because of the same switch.

 

[89Mock]

Brakes work.
Brake LIGHTS don't come on when I push the brakes.

I think I cut too much off when I did the swap. Apparently there needs to be SOME tension on the brake switch when it is connected to the master cylinder. I plan on measuring the thickness of it at some point. One DIY showed it being about 0.241" so I'm guessing mine is closer to 0.230 or skinnier and I'll need to add some duct tape or something to make up the material I took of. It seemed to be pretty tight when I put the bushing back in.

I don't recall unplugging the switch. I think I just removed it and left it connected.

 

[kastein]

The fact that the lights don't work is why the cruise doesn't disengage.

 

[89Mock]

I assumed so. Pretty sure if I push the brakes hard enough the cruise disconnects. Lightly tapping the them doesn’t turn off cruise. Either pushing them much firmer canceled it or the vehicle canceled it under a certain speed because I had it cancel yesterday. When I get time I’ll mess with the switch to see if the lights are always on, or not coming on. I ground the booster down to where the switch would sit flat and the bolt slid through somewhat easily. Saw NickInTome’s video saying the switch should have some resistance which is why I believe I took too much. I ground down until the bolt went it thinking it needed no resistance and the spring would compress when I pushed the brakes.

 

[denverd1]

My old 91 was the same way as is my 2000. The switch is adjustable.

Adjustable mounting of it? Changing the switch itself? Did booster on my 98 but didnt get rod depth set right or something. Brake lights stayed on until I shimmed the pedal

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