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Power Booster

J

jcwxj

NAXJA Forum User
Location
Hazleton pa.
I have a 86 xj and I need to replace the power brake booster. I was wondering if anyone has any helpful tips that I may need? Or if this is something I should let a professional do? I have done basic brakes and master cylinder replacement. It doesnt seem to difficult 4 mounting bolts and pedal linkage. Please help.
 
It should be fairly simple. I've done this on other vehicles before, and if you don't disconnect the master cylinder from the brake hardlines, you usually don't even need to bleed the brakes (but I usually do anyhow, just to refresh the fluid.)

Drain the master cylinder about halfway, remove the two mounting stud nuts, and pull it (GENTLY!) out of the way. This frees up the booster.

Remove the mounting stud nuts and vacuum line, and you can access the thing. You should be able to get enough room to replace it.

Oh - if you're going to the trouble to replace the booster, I'd also highly suggest you change the vacuum lines and check valve while you're about it. You'll have to pull them anyhow, so it doesn't add anything to the job...

5-90
 
Also, make sure you change it out with a '95-96 booster, rather than a new '86. The newer booster are dual diaphram and will increase your braking power substatially.
 
SCW said:
Also, make sure you change it out with a '95-96 booster, rather than a new '86. The newer booster are dual diaphram and will increase your braking power substatially.
Click to expand...

That also means replaced the master cylinder correct? I'm planning this swap somewhere in the future.
 
lawsoncl said:
That also means replaced the master cylinder correct? I'm planning this swap somewhere in the future.
Click to expand...

I'd have to check, but I don't think that's necessary. You're not changing anything hydraulic - just the part that amplifies the force you apply to the m/cyl pistons... As long as the m/cyl mounts up to the booster, you're fine.

5-90
 
I was thinking the interface between the master and booster was different and they wouldn't mate up. Heck, if all I need to swap is the booster that would make life easier.
 
Make sure you look inside the booster for fluid after you remove the master cylinder. If it has any brake fluid in it you will need to replace the master cylinder at the same time.
 
So just so I understand a booster from a 95-96 will fit . I just put a new master cylinder on 2 weeks ago, as long as I dont need to change that and everything else swaps easily than maybe I willl go with the newer version.
thanks,
jcwxj
 
Converting to the dual diaphragm booster requires the newer MC. The old MC's won't properly seal against the new booster; the old, single diaphragm boosters didn't need a vacuum-proof seal like the dual diaphragm boosters do.
 
Point well taken on used brake parts and Pa mts. But as for xjbubbas point about a new master cylinder.Does he mean new as new from a 95-96 xj or will the new master cylinder I just put on my 86 (2 weeks old) seal on the newer brake booster?
jcwxj
 
What I mean is the physical design of the MC's for the '94 and early-er single diaphragm booster won't properly seal when mounted on a '95 or later double diaphragm booster. The MC on a dual diaphragm booster must have an air-tight seal between the MC and the booster to work properly. Your new '86 MC won't work on the '95-'96 double diaphragm booster.
 
Ah, ha. I hadn't looked into that.

I don't suppose there's any way to make an early m/cyl work with a late booster, is there? Which part of the interface does the sealing? Is it something that could be potentially machined into the early m/cyl to retain the nice cast part, rather than the cast aluminum m/cyl with the plastic pressed-in reservoir?

Or am I going to have to take a look at both assemblies firsthand, and see what can be done on my own? :laugh:

5-90
 
There is also an angularity to the face of the '95 up booster that will put the old MC into the hood when closed.

I'm not a fan of plastic under the hood either, but I like to stop :D I figure it worked for the '95 and up, and still does to this day, so how bad could it be?
 
The dual diaphragm MC's have an o-ring arround the snout to seal on the booster. I haven't looked to see what it would take to modify the booster and/or the MC. I saw a post on Pirate4x4 indicating the use of home-made gaskets and "goop" resulted in sealing the MC to the booster--that's not an acceptable approach for me. I'm sure an adapter could be fabbed to do the swap, but have no idea if it's practicable to do so. It may be cheaper to just use the latter MC.

I just recently installed a Mercury Marque MC on my '88 booster to get more volume. I'd also like to install the dual booster and be able to keep the MC I just bought--it's not the money in my case, it's just that I can't find a dual diaphragm MC that will fit the '95 XJ booster that has the identical piston size of the Marque MC.
Check out pictures on napaonline.com http://napaonline.com/masterpages/N...708&Description=Brake+Master+Cylinder+-+Remfd
 
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