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Unread 10-23-2012, 09:33 PM   #1
parkerm26
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1993 YJ Wrangler 
 
Join Date: Jun 2009
Location: Norwell, MA
Posts: 525
Warning: '86 e-350 master cyl. Swap unsafe

UDATE FOR ANYONE DOING THE '86 E350 MASTER CYLINDER UPGRADE w/ REAR DISK BRAKES: taking the O-ring out of the proportioning valve will not make this master work with 4 wheel disk brakes! this is a major safety issue.
This brake master is not designed to work with rear disks. this master sends more pressure to the rear and almost none to the front. doing this heats the rear fluid because it is all channelled into one main line. this causes damage to the master and cover gasket.
Further; the top clamp interferes with the vacuum brake booster and creates uneven pressure on the lid gasket. this causes the rear brake reservoir (smaller, front reservoir) to empty as fluid returns from the lines and runs along the bottom side of the cover. it then leeks out through the gap between the gasket and the reservoir. eventualy the reservoir empties and begins to plunge air into the lines. since the front brakes do not work correctly with this master, and the rear empties, you loose brakes COMPLETELY. luckily i have a 5 speed and the air pressure was enough to come to a slow stop with downshifting and get home without crashing.

PLEASE DO NOT ATTEMPT TO USE THE '86 E-350 BRAKE MASTER CYLINDER WITH REAR DISK BRAKE CONVERSIONS.

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Unread 10-23-2012, 09:33 PM   #2
parkerm26
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The '69 corvette bake master cylinder (w/ power brakes: the 1 1/8in bore) is supposed to be appropriate for disk brakes in the front and rear. I just received my new corvette master. I will update soon but i expect it to work flawlessly. the top cover clamps are not in any danger of interfering with the booster or other under-hood components. Yes i know the bore is larger so it will be harder to push but thats okay with me. I have huge dual pistons in the front and MASSIVE single calipers in the back. I'm not worried about them being too hard to push. I will update ASAP about the stopping power. as soon as i get this master bench bled, installed, and the brakes completely bled i will take her out for a spin.
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93' YJ: 14 Bolt, Dana 60, 38's, New hot galvanized frame. Pretty much done... for now.
Check it out: http://www.jeepforum.com/forum/f22/yj-rustoration-1327569/
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Unread 10-24-2012, 01:52 PM   #3
1SASjeepster
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1992 YJ Wrangler 
 
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For my 1992 YJ, I used the 1975-1976 Ford Lincoln Continental Master Cylinder. It is designed for four wheel disc brakes and it fits right onto the YJ's Vacuum booster without modification. Some have wrote that the YJ pushrod has to be lengthened 3/8" but my worked fine. I used a Wilwood adjustable proportion valve also.

Thanks for the "heads up" on your conversion. Good luck with the corvette master cylinder.

Take care,
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Unread 10-24-2012, 02:48 PM   #4
parkerm26
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1993 YJ Wrangler 
 
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what size is the bore on the continental master?
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93' YJ: 14 Bolt, Dana 60, 38's, New hot galvanized frame. Pretty much done... for now.
Check it out: http://www.jeepforum.com/forum/f22/yj-rustoration-1327569/
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Unread 10-24-2012, 03:43 PM   #5
1SASjeepster
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Off hand, I don't know... but I did when i installed it a few years ago. Any auto parts place that has the part should be able to tell you though. The master cylinder is larger than the current YJs.

Take care,
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Unread 10-24-2012, 03:48 PM   #6
skyj
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1990 YJ Wrangler 
 
Join Date: Jan 2011
Location: Helena, MT
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Quote:
Originally Posted by parkerm26
UDATE FOR ANYONE DOING THE '86 E350 MASTER CYLINDER UPGRADE w/ REAR DISK BRAKES: taking the O-ring out of the proportioning valve will not make this master work with 4 wheel disk brakes! this is a major safety issue.
This brake master is not designed to work with rear disks. this master sends more pressure to the rear and almost none to the front. doing this heats the rear fluid because it is all channelled into one main line. this causes damage to the master and cover gasket.
Further; the top clamp interferes with the vacuum brake booster and creates uneven pressure on the lid gasket. this causes the rear brake reservoir (smaller, front reservoir) to empty as fluid returns from the lines and runs along the bottom side of the cover. it then leeks out through the gap between the gasket and the reservoir. eventualy the reservoir empties and begins to plunge air into the lines. since the front brakes do not work correctly with this master, and the rear empties, you loose brakes COMPLETELY. luckily i have a 5 speed and the air pressure was enough to come to a slow stop with downshifting and get home without crashing.

PLEASE DO NOT ATTEMPT TO USE THE '86 E-350 BRAKE MASTER CYLINDER WITH REAR DISK BRAKE CONVERSIONS.
I'm curious with your results I have been running my E-350 on my YJ for close to a year now with no ill affects. I have a Ford 8.8 rear with discs and it works very well. I have not noticed low fluid in the rear brake fluid reservoir, nor does the clamp interfere with the vacuum brake booster, or leaks
This is the first I have heard of your problem and I researched it well on pirate4x4 and here I always check my fluids ( always clean not burnt) and haven't lost a drop since I did the swap.I'm curious as of why yours is doing this?????
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Unread 10-24-2012, 04:53 PM   #7
bgredjeep
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Results may vary. There are plenty of these running around with the setup you state will not work. With brakes you can't always just throw parts together and make them work. Based on your description of most pressure going to the rear, heat should be the last issue to worry about. If you are actually getting more pressure in the rear, the brakes would be locking up in the back every time you try to stop.

I personally used the stock yj master for years with the rear cadi calipers. It was fine until I swapped to some different rear calipers (80s Monte Carlo). This required a larger bore master (soft pedal) so I swapped one from a grand marquis. It was larger bore and mad for disks. I had to use some adapter fittings, and made a small spacer to fit between the booster and master. After this update its rock solid braking again.
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Unread 10-25-2012, 03:45 PM   #8
parkerm26
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I just don't want anyone to experience loss of brakes because of this. i thought it was great when i first got it but now i am definatly not safe with it in there. yes the rear brakes do lock up and the fronts do not seem to be doing anything. but this is only on hard stopping in the rain. it is managable but sooner or later it could cause a serious problem for me. i will post up results for the corvette master since it just got here the other night i have not installed it yet.
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93' YJ: 14 Bolt, Dana 60, 38's, New hot galvanized frame. Pretty much done... for now.
Check it out: http://www.jeepforum.com/forum/f22/yj-rustoration-1327569/
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Unread 02-10-2013, 05:04 PM   #9
dauster500
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1987 YJ Wrangler 
 
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soooo any updates?
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Unread 02-10-2013, 06:08 PM   #10
timatoe
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Quote:
Originally Posted by parkerm26 View Post
.........taking the O-ring out of the proportioning valve .......
In and of itself is a safety issue and should not be done.
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