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Brake Booster

ken johnson

NAXJA Forum User
Location
Kentucky
Should I be hearing a loud swoosh coming from under the dash inside my 89 xj with standard power brakes.? Only when I apply my brakes!
 
Sounds to me like a bad power booster.

Try this: engine off, pump the brake pedal three or four times and then hold pressure on it. Start the engine--if the pedal drops a little your power booster is working, if not, replace it.

If you have to replace it suggest 95+ XJ MC and dual-diaphragm power booster upgrade.
 
Yeah. If you go 97 Booster, you'll have to swap the rods out.

You have to modify the rod if you are doing the Grand upgrade, or modify the rod/swap the brake pedal assembly if you are doing the 95+ XJ upgrade.

Lots and Lots of write ups on NAXJA for both.
 
If you go with a 97 booster, the rod is too long. It has to be swapped out; unless you like the pedal scratching your nuts?
 
If you go with a 97 booster, the rod is too long. It has to be swapped out; unless you like the pedal scratching your nuts?

Very graphic! LOL!
 
To answer the original questions NO you should not hear this. ... this is just what i had an spotted it about 30 seconds before my foot went straight to the floor when braking yesterday so be warned it could pack up at any moment.

I thought it was the master cylinder ( i dont know why) so swapped that out and was totally wrong. Its the booster.. I'm half way thought swapping it out nnow for one of a 2000.
 
what year booster? I got the whole lot (booster and MC) from a year 2000. The rod is too long so i will cut, sleeve and weld that and getting the flat spot on the end of the rod for the brake light switch too about 6 tries but its pretty straight forward.

I reused the metric line fitting on the MC out of the new model and then just made up some brake lines as they need to be longer to as the outputs on the new MC are on the drivers side and the old one are not. Also the new MC is moved forward a few inches because of the bigger booster. Not a bad swap and its great to have some faith in the brakes.

I wish i had got the $16 double flair brake line tool for Harbor Freight before i did this. I would have made life pretty easy!

If anyone wants a almost new master cylinder for a 87 on they can have it for the cost of shipping. I pad 57 bucks for it and used it for 2 hours before i worked out it was the booster.
Dave
 
I used an '01 XJ booster. I Used a 1/4" spacer between the firewall and the booster, but the brake pedal was still 1" higher than stock. I didn't want to pull the MC out, so I pulled the brake pedal, and welded a "nub" on the back side , drilled a new hole for the pedal, and all is well. The new hole is 1/4" lower, and 3/4" behind the old hole (actually 1 1/16 back from the front edge of the pedal.
The '88 XJ booster rod was 4&15/16, while the '01 rod was 5&15/16. Because of the angle at which the '01 booster sets to the firewall, the new hole will be lower on the XJ pedal (1/4").
If I had known all of this before I did the swap, I would have cut off the end of my old booster rod and would have sleeved and pinned it to the new booster rod, after shortening it--I wouldn't weld on the new rod, for fear of "melting" the booster's internal seals/gaskets.
 
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