WJ Booster Incompatible with MJ

[cruiser54]

There is a critical measurement between the booster pushrod and the master cylinder. 

 

 

booster rod.pdf

[Salvagedcircuit]

Thanks a ton for the document Cruiser!

I don't know if my booster is adjustable as shown in the document, but this at least gives me some insight master+booster fitment and booster troubleshooting procedure.

Thanks.

[cruiser54]

I learned that lesson the hard way many years ago.

[Salvagedcircuit]

Curious, was your booster shaft too short and you had reduced brakes and pedal drag? I was hoping that by purchasing a new 3rd party booster and master designed for the identical vehicle that the two parts would have the proper fitment.

[cruiser54]

Booster rod was too short. 

You can measure it yourself. 

 

[Salvagedcircuit]

I wonder if the 1999-2001 Grand Cherokee service manual mentions the acceptable push rod clearance values. I should try and find the WJ service manual.

[cruiser54]

1/32" will be fine. You want it to have teentsy bit of clearance. 

[Salvagedcircuit]

Good news all,

One of my theories was correct: The rod inside the booster was not lined up with the master. Because of this, the booster rod is now off center and the master is slightly damaged. This is why nothing was flowing from the master cylinder outputs when the brake was pumped.

 

Also, I grabbed the '96 brake pedal assembly from the JY and it fits perfectly. The brake light switch housing is simpler and more robust, but I still have to modify it for the automatic transmission cable clip bracket which I will have to weld.

 

In addition, I ordered a new old stock '96 dual diaphragm mopar booster+master from omix-ada / morris 4x4. It came completely dented and is not unusable. No packaging material was used.

The WJ booster I ordered from napa was unpainted and remanufacturered which was not mentioned. It is a centric part, in case anyone was curious.

 

After my testing with the new WJ brake setup, I discovered that my main brake line from the front-back is shot.

 

I will update with photos later on.