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booster/mc swap

ToubabouBob

NAXJA Forum User
Location
Ivory Coast
I've read your forum over the years but I think this is my first question here.

The brake booster in my 98 XJ is shot. I live in West Africa (don't worry, you
won't get Ebola from reading any further) and the junkyards in my area don't
have anything for an XJ better than what I have. I can get a new booster
from the US and have it shipped now for an extra $200 or brought here by a
friend if I wait a month. It's a 5-speed so I can deal with the hard pedal a while.

Or, somone here proposed a booster from a WJ (p/n 5212-8102AB) with its
master cylinder attached, all for $60. I have seen write-ups on putting one of
these in a pre-95 XJ and lots of guys have done it. My Jeep just has 235s but
it has terrible drum brakes that I would like to replace with GC discs sometime.

What do I need to do make it fit besides lengthening the link to the brake pedal?
Can I just use my XJ proportioning valve and use the same lines from the MC
to PV, (looks like they'll just bolt up) or are there flange differences?
If I do one day get the rear discs, do I need a different PV or can it be altered?

Thanks in advance for any advice.
 
LOL, You're funny.

I've done this in a couple XJ's.

The WJ booster works great. Very easy swap.

When you get the WJ booster and master cylinder be sure to get the brake line fittings with it. They're different but use the same diameter brake line. I took the WJ fittings and reflared the XJ lines from the PV to the MC.

I reused the XJ master with no modification.

Also, you'll want to make sure to get the booster spacer that comes on a WJ. It's about 3/8" thick and fits betweent the booster and firewall. You'll want to put that back on your XJ.

You'll have to grind the end of the pedal rod flat as well. All of that is covered in the common write-ups available online.

Keep me posted. I'll be glad to help. (From here, away from the Ebola.)
 
I took the WJ fittings and reflared the XJ lines from the PV to the MC.

Thanks for the quick reply.
I'm not really a mechanic and brake lines are unfamiliar territory.
Do I cut the flare end off the line, remove the XJ fitting, put on the WJ fitting,
and then reflare the line? Is there a special tool to reflare it?

I've got a shadetree (literal) mechanic here who I hope would have what's
necessary to get this done. When we couldn't find the right booster, he was
talking about adapting one from a Toyota.

Edit: I just now saw your second post and the writeup. I'll check it out.
 
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Thanks for the quick reply.
I'm not really a mechanic and brake lines are unfamiliar territory.
Do I cut the flare end off the line, remove the XJ fitting, put on the WJ fitting,
and then reflare the line? Is there a special tool to reflare it?

I've got a shadetree (literal) mechanic here who I hope would have what's
necessary to get this done. When we couldn't find the right booster, he was
talking about adapting one from a Toyota.

Edit: I just now saw your second post and the writeup. I'll check it out.


Yes, you have it right. You want to replace the XJ fitting with the WJ fitting at the MC.

Yes, there's a special tool. Around here you can rent one from the autoparts store. Perhaps you could try that? They're kind of a pain in the butt to operate but you get the hang of it. Also, buy a brake line cutter. They're cheap and very useful.
 
Well, I was going to wait a while until I could find a good used
booster for an XJ or a better-looking WJ one than I found but a
couple of things happened which made me see I need to get rid
of the hard pedal now. Saturday I narrowly missed hitting two guys
on a motorbike and Sunday i was wounded during a robbery in the
bush and my sweet wife had to drive the Jeep for a while.

So, I had my mechanic go get the rusty-looking WJ booster/mc and
do what he needed to adapt it. He got it put in today and the booster
has a lot of power. He reused the XJ lines from the mc to the prop valve
and said they fit and they don't look like they are leaking. The pedal is
a little soft and I think the system still needs to be bled somewhere and
the rear brakes need to be adjusted better, which he should get done
tomorrow. But it stops much, much better. So thanks for your advice.
 
Wounded during a robbery in the bush.......I'm guessing this is a NAXJA Tech forum first. Sorry to hear of your injury and hope for a swift recovery. Glad you were able to see a braking improvement.
 
Thanks for the kind regards. I tried to back away from the first two armed
men 50 yards in front of me, but there were two others behind. One threw
a machete at the Jeep and cut my forearm badly. The took money and cell
phones and let us go. We got to one of our village churches where I got a
bandage and later was sewn up in the city. The doctor says it should heal
completely, praise the Lord.

Bob Engelhart, Baptist missionary
 
Well, I was going to wait a while until I could find a good used
booster for an XJ or a better-looking WJ one than I found but a
couple of things happened which made me see I need to get rid
of the hard pedal now. Saturday I narrowly missed hitting two guys
on a motorbike and Sunday i was wounded during a robbery in the
bush and my sweet wife had to drive the Jeep for a while.

So, I had my mechanic go get the rusty-looking WJ booster/mc and
do what he needed to adapt it. He got it put in today and the booster
has a lot of power. He reused the XJ lines from the mc to the prop valve
and said they fit and they don't look like they are leaking. The pedal is
a little soft and I think the system still needs to be bled somewhere and
the rear brakes need to be adjusted better, which he should get done
tomorrow. But it stops much, much better. So thanks for your advice.

This is scary. The Wj uses totally different fittings than the XJ at the master, if you used the WJ master. If you kept the XJ MC then you are fine. I used the flex line from the WJ and then cut and flared the prop valve side for the XJ fittings.
 
Thanks for replying and expressing your concern. There are a few other things on this third-worldized Jeep that might scare people, too, but somehow it holds together.

I was wondering, too, if the flares would line up and since the pedal is soft, I took it back in to the mechanic this morning.

The mechanic did use the lines from the XJ prop valve to the WJ master cylinder. He said there was no difference between the flares. We took it all apart and I took the photo on the left with my cell phone camera. On top is the connector and flare end of the line that was supplied with the WJ mc, on the bottom is the XJs line end from the prop valve which enters the mc. He sees no difference and I admit I see no significant difference. The line ends appear to have the same diameter and the same form. Or, are the flare differences more subtle than we are seeing? My XJ is a 98 by the way.
IMG0009A_zpse079c0a0.jpg
IMG0009A_zpse079c0a0.jpg

IMG0009A_zpse079c0a0.jpg
IMG0016A_zpsbc82e59e.jpg


In the photo on the right showing the forward outlets, the XJ mc is at left, the WJ at the right. They look to have the same form.

I also noticed that the XJ mc would not fit on the WJ booster - the studs on the WJ are about 3/4 inch wider than the for the XJ.

Anyway, the pedal is soft and there is apparently air in the system. The mechanic thought maybe there is a leak in the seal at the back of the mc toward the booster and is out now trying to get a replacement.
 
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not a bubble flare versus a double flare, but the thread pitch in the WJ is metric and the XJ standard? At least I thought so? perhaps not . I runs WJ booster and MC but I cant remember the thread pitch at the MC.
 
Thanks for the responses and for wanting to help me get this right.
I sure don't want my brakes to fail.

I wrote a few minutes ago to a retired Chrysler mechanic and asked if
he knew what kind of fittings my 98 mc would use and he replied "your
brake lines should be metric at the proportioning valve/master cylinder,
and SAE downward towards the other brake lines."
He owns a 99XJ and
recently changed several of his lines. He did not know about the WJ,
though. The following link says clearly that the WJ mc lines have metric
fittings. http://www.4x4wire.com/jeep/tech/brakes/xj_wjbrakes03/booster/index.htm

So, the master cylinder my 98 had, Mopar P/N 4761-941, has compatible
fittings with the WJ mc. That means that XJs from 95-later that use that
mc can swap to a WJ booster/mc (if they would ever want to) and use
the same lines to the prop valve.


I got the Jeep back today from the mechanic and the brakes work very
well. They adjusted the rear brakes and spent more time than the day
before purging the system. As a side note, I got a call saying that the
area gendarmes surprised a band of four suspected of the robbery and
arrested two and the others are at large.
 
Ya know, come to think of it, you have a good point. I didn't even think about yours being a late model.

The only time I've ever upgraded to a WJ booster was when I had an early model (two 93 models and a 94 model) booster with a single diaphram. There was no reason to upgrade a late model as it's an OEM dual diaphram but you can't get the part so you're using a WJ booster. So, yes, it would make sense that it would use the same fitting.
 
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