Master Cyl Swap from 90 Cherokee

[NiftyFifty]

I know some guys asked about a master swap that was of size and not a custom job and I managed to find one off of a 90 Cherokee at the local wrecker that was the same length as original and proceeded to see if it would work.

Without much effort at all it fit nicely into place. So here's the procedure:

Remove the original master and then remove the push rod and yoke right from the pedal arm. This will need to be adjusted or cut later, as I can't speak for every model and I don't know what rod or length you have, but my old push rod slides right into the new master perfectly and basically the bore isn't changed as the size is the same.

Get a piece of 1/4" flat steel plate and trace the mounting patern of the original master cyl. Cut the edges of the plate to make it close to the original size of the backing plate on the master and mark and drill the three original spaced holes traced from the orig. master cyl. I think their about a 3/8" hole, but you may want to go just one step bigger for a bit of wiggle room to get the bolts in.

Then quickly placing 3 bolts through the holes into the old master, carefuly trace the outside of the bore of the old master and cut that hole "approx 3" with a cutting torch or whatever tool you have. Now place the new master onto the plate with the 3rd hole to the bottom and mark where the 2 new mounting points need to be: Now drill out the holes to 5/16" and use two regular or carriage bolts pushed through from the backside of the mounting plate. I welded the bolts on then ground everything fairly smooth, and welded and grinded until I had little showing above the plate, but enough that there was still strength of the original bolt head and the weld.

Install the plate to the truck with only the 2 top holes receiving lock washers, or use longer bolts and use lock nuts on the back of them to secure. For the cherokee master cyl I had to grind just a tiny bit off the bottom bolt head edge to get it to fit tight to the plate but it's very minor and won't affect the strength. The only other issue is one of the front line to the proportioning valve is in the way of the steering clamp and just need a new line made and re routed from the bottom up rather then around the end. (pics below)

Now feed it through the top with the mounting side facing down and slip onto the new mounting studs and put on locking nuts or lock washers and tighten. This does require some changes from the original line, but you can purchase felxible line and adapters at most jobber spots, for me I ran all new line so wasn't an issue.

Hope this helps anyone looking to go to a 2 res system.

[NiftyFifty]

Here are the pics of the line change to the proportioning valve, it should have been tighter, but I don't have a good tube bender so it's a little longer, but will fit and work fine.

I ran all 3/16" line as that's what the stock cherokee uses and the rear diff I plan to get will be that and the front brakes will be set up for that size.

[HanksB3B]

I won't ask why...because the only answer is "because I can", but that looks mechanically creative to me.

Hank

[JoelOkie]

The advantage of the double resevoir is fairly obvious. I like the idea of being able to keep one set of brakes operable in case of a failure at one axle. Looks very ingenious. Have you been using it? Joel

Edited May 31, 2010 by JoelOkie

[Merle Coggins]

I like it. I'm going to look into it further when I get a chance. I see that you have the proportional valve mounted right to the M/C. Could it be remote mounted to allow more clearance for the plumbing? It looks like it should be possible.

Merle

[oldmopar]

Looks like a good fit I just did may brakes a few months ago but I will have to consider this option.

[1955 plymouth]

nice, looks like it wasn't too bad to adapt. I need to do something like this for the '55 Plymouth Belvedere I have as a project for me and my son, it does not have a master cyl. I saw one on e-bay last night for about $80, perhaps I will try to adapt another instaed. After all it is just a fluid resivour with a plunger inside to push fluid right...

[JoelOkie]

I like it. I'm going to look into it further when I get a chance. I see that you have the proportional valve mounted right to the M/C. Could it be remote mounted to allow more clearance for the plumbing? It looks like it should be possible.

Merle

Good question/point there Merle. I have enough trouble working in some of the tighter places. I am thinking I would like to go with it also. Joel

[NiftyFifty]

Looks tight, but really there is lots of room beside and below, and you can put the valve further down line, but that may make for even more modification to the lines and then trying to find somewhere to mount. Maybe on a car there is less room, but for this it was no issue at all as long as it's on the left side as you face the front.

The why of course Hank is so that you have a completely better braking system compared to the stock, and also on a hard brake you actually have enough fluid to do both side and ends...not a left side grab to through you in the ditch or right to oncoming traffic. Haven't had the truck out yet, ways to go before that but absolutely no reason it won't work, as the valve is adjustable once I get things going and make it perfect.

This is a pretty minor operation so you don't have to have a running mechanics shop to do it, even the 3" hole could be done with a lot of drilling and a good steel chisle

[PatS....]

This would be a great swap for a disc kit. Better brakes and easier to get parts.

Nicely done!

[Frank Elder]

This would be a great swap for a disc kit. Better brakes and easier to get parts.

Nicely done!

Throw in a jeep rearend with discs and you have no more wheel cylinders to worry about either......

[NiftyFifty]

Throw in a jeep rearend with discs and you have no more wheel cylinders to worry about either......

I'm going to a jeep rear end, but still drums...picked up another diff from a 93 Wrangler today....looks like it will be a great fit! I think once you go to rear discs you loose the leaf springs and they move into a strut suspension, but I could be wrong.

[NiftyFifty]

i always get pm's asking how the set up is working, and I can report that I'm in the middle of my 3rd year and the cherokee master is still working great and the brakes feel good with no noticeable grab on one side and a Deffinate feel that the front are doing their job as the main stopping force.

I did this whole set up with the engine trans in, but if out you could possibly skip the plate mount and drill holes in the actual cross member

[Don Coatney]

Looks great! What is the bore size of the master cylinder and do you have disc brakes on the front and drums on the rear?

[NiftyFifty]

I'm drawing a blank on the bore size but as I recall it would be a direct fit for the stock hole if it wernt for the mounting spots being in the wrong spots.

I do have the front disc set up in the front and I run drums in the back with my 93 Jeep YJ rear end.

[pflaming]

I made a mount and mounted my Cherokee Master Cylinder today. I had friends at a quality machine shop build my mount. (I had two made while I was at it). When I put it on, it fit perfectly. With allen wrench bolts, no modification to the MC was required. My proportioning valve hangs on the passenger side of the MC, down and below. It installed with the MC with no trouble.

Tomorrow I will remove the new front 1/4" lines and replace them with 3/16" to conform to what the system was servicing in the cherokee. I haven't decided where to put the stop light switch, probably on the front lines. Once I had all the little things ironed out for my truck, this is a very easy swap. My parts service man was amazed at this swap. This MC and valve cost me $40 compared to a new OE MC at $149.

When my camera arrives from Maine, I will post pictures.

The master cylinder is a Bendix 6241 C (4028 SS 39). The valve number is: Q4KH3406 (3276). The source is a 1997 Jeep Cheriokee. It comes from the same vehical as my rear axle.

Edited July 20, 2012 by pflaming
Parts numbers

[NiftyFifty]

I found a pic of my set up on the bench, and yes the Prop is on the passenger side. I might have had to do a bit of bending or change a line to make it fit nice and low to avoid the starter and steering box...but it's kind of a blank now.

Just be careful when you cut your push rod...give youself lots of adjustment on the threded part that pins to the pedal shaft

I see I posted that pic earlier...really thought I had a better one when I had the engine out of it in place.

Edited July 20, 2012 by 4mula-dlx

[pflaming]

Having problems so went surfing: FOUND THIS SURFING FOR ANSWERS. This answer was on line, so it is someone elses research.

"I've seen this question pop up pretty often, but never seen a definitive answer. So I decided to drive to the parts store, and figure it out.

I replaced the brake lines in my Fiero with the Fiero Store's stainless steel pre-bent lines, and bought an extra proportioning valve and 3-way rear block just in case my old ones were unusable. The prop valve was fine since it was sealed in the spare tire bay, but the rear block was a corroded mess. I cut the old lines off, put the block in a vise, and used a couple Snap-On 6-sided sockets to get the old fittings out of the block. Then I cleaned it off with a wire wheel:

Now, when I was seeing how many different brake line and fitting sizes there were, I was surprised to find there were only two (not counting the two lines going to the master cylinder on top of the prop valve). The big fitting, with it's 6mm (1/4) line, and the small fitting with it's 3/16 line. So I took these to the parts store.

I hate to admit it, but yes, I went to Auto Zone. This is probably the only store in town where I could go behind the counter and do the research in the parts area for half an hour, going through all the fittings. Here's what I found:

The brake lines are European thread bubble flare. Yes, a Pontiac, built in the USA, has European brake lines. I believe this is because the parts probably came from Canada. This is an example of the lines they have:

This line is 3/16 x 08" (line size x length) (4.7mm x 20.3cm). metric thread/bubble flare. European thread bubble flare. All these lines begin with the designation PAE-3__, where the last two numbers are the line length in inches.

They also had PAB-3__ line, which is US thread bubble flare - these will NOT work on the Fiero. The fittings are a different thread.

(Again, the two lines that go into the master cylinder are different, and appear to be regular American-style double flare lines.)

Now the fittings:

First, the large fittings. size is M14 x 1.5 bubble thread size, 6mm tube size. They sell these in a 5-pack, made by the company AGS.

part # BLF-53C-5

barcode # 077146372520

$3.49

The small fittings: size M10 x 1.0 bubble thread size, 3/16 tube size. Also a 5-pack by AGS,

part # BLF-39C-5

barcode 077146368813"

$2.99

Monday morning: I think it's Europes' revenge for the USA going independent and switching from tea to coffee. Yes the fittings on the MC are metric (#12) and the fittings on the valve are SAE (9/16). That cost me a LOT of time.

Edited July 23, 2012 by pflaming

[pflaming]

How my valve is mounted. This has been a challenge. More when I finish.

[pflaming]

We presurized the system with a new sprayer. We could get fluid at all corners and no leakers but could not get pressure at the pedal.

It could be a faulty master cylinder but I "bench tested" it and . . . I know getting pressure a/g one's finger is not a text book test.

Question: What would happen if the proportional valve was mounted backwards?

[TheMoose]

We presurized the system with a new sprayer. We could get fluid at all corners and no leakers but could not get pressure at the pedal.

It could be a faulty master cylinder but I "bench tested" it and . . . I know getting pressure a/g one's finger is not a text book test.

Question: What would happen if the proportional valve was mounted backwards?

I put disc brakes on my autocross car & had a similar problem.

We could bleed the brakes, had no air in line & pressure at all 4 wheels & good pedal, 5 min later no pedal.

Turns out we used too small of a master cylinder, put a bigger one on & problem solved.

No idea if it's your problem but thought I'd throw it out there.

[NiftyFifty]

Am I missing something or did you block one of the ends on the prop valve?? Should be 3 lines coming off of it, or is it just hidden in the pic.

If you bled them the way I explained you should have pedal pressure, if you used a single man bottle type I'd try the manual way. Other then that recheck for any leaks, but if not then you got a bum MC unfortunately.

[pflaming]

My proportioning valve was connected as shown. There is a third port, like yours but it has the port plug and an adjustment screw inside. Only two ports were used on the '97 donor truck.

[perry jones]

Check out my master cylinder conversion on 3/1/11. I also swapped out the rear end with a Jeep Cherokee. Only had to notch the Cherokee spring pads and add a 4 degree shim on each side. The drive shaft and U joints interchanged. Also put in Charlie's disc brake kit. Put in a rebuilt steering box. Now doing a new wire harness. Perry Jones 505-281-1177

[NiftyFifty]

My proportioning valve was connected as shown. There is a third port, like yours but it has the port plug and an adjustment screw inside. Only two ports were used on the '97 donor truck.

Oh ok, deffinately a different set up then, I can't see any reason why it should work then, but as I say make sure you do a manual bleed if that doesn't cure then your back to the wrecker