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I apparently had a leak in one of my flexible brake lines after storing my '66 at my folks' house for a few months, because last time I got in it to take it for a spin and blow out cobwebs the pedal went to the floor. I have had a dual MC on this thing for a few years now and it worked great. So I just assumed that I must have leaks in at least one front and one back line to empty both bowls. But when I pulled the cover, the front bowl (for rear brakes) is full and the rear bowl (front brakes) is bone dry.

Isn't the point of a dual MC to have separate systems? I am worried now. I have absolutely no pedal at all which means if this had happened going down the road I might as well have had the old jelly jar! Ugh.

Any ideas how this is possible?
 

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Double check your plumbing, something isn't right. Also, if one of your rubber lines is bad, the rest probably are too.
 

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If the rest of the rubber lines were bad though, wouldn't both sides of the MC be drained?

I'm curious to learn what you find out. I've got a jelly jar MC right now and was going to switch to dual MC... but if it doesn't do anything, then I'm not going to put the money into it.
 

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Disclaimer: Not saying this is the right way to do things. That said, I plumb the brakes completly seperate front and rear, no "H" block/portioning valve. Then install a manual portioning valve in the rear brake line to adjust bias front to rear.
 

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Folks. The dual master has been a safety requirement since 1968 models (67?). This never meant failure proof. With the single compartment master any significant leak gives no brakes. The two comparment master gives two separate unconnected hydraulic systems. Both systems have to fail to give you no brakes. With a vehicle that is frequently driven it would be very unlikely that suddenly you lose fluid and or lose line pressure on both ends, both systems. If during storage one systems leaks almost dry while the other is going bad you could take off andf have no brakes!

Years ago I had a 37 Ford. It was in incredible condition at the time. In 1971 I drove it frequently to work. On the expressway I was comfortable driving 65mph with the traffic. By the way the 37 Ford had mechanical cable operated brakes. No problem losing brake fluid and if properly maintained/adjusted were damn good brakes!

My point is any technology is an advantage if maintained...working. Dual master is no help with front and rear failure...yup. Does ABS help with a failed system? Traction control?

Slim
 

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If the rest of the rubber lines were bad though, wouldn't both sides of the MC be drained?

I'm curious to learn what you find out. I've got a jelly jar MC right now and was going to switch to dual MC... but if it doesn't do anything, then I'm not going to put the money into it.
Kelly,

If one of the front rubber lines has dry rotted and is leaking, that could mean that the others are not far behind. In your case, if one of them seemed fine but went bad while driving, voila, you have no brakes.

It is NOT a myth about the dual MC, it's not that you should get one, it's that you need one. They are dirt cheap, CJ has the lines prebent. You can get a USA made, raybestos master cylinder new for under $80. Total is only $100. You can do it yourself too.

Although, I just read your signature (man, your car is awesome!), you are in the classic situation of having a manual tranny and wanting a dual master cylinder WITH power brakes. I think that gets trickier as the clutch can be in the way. I think there is a booster that works though.

PS - I am sure someone will chime in saying they have driven a single master for 45 years, and they are fine. My response would be, a properly maintained system IS fine. I wouldn't run out to buy a dual setup. BUT, why on earth when these cars costs thousands upon thousands of dollars would someone not add redundancy to their brakes for $100?
 

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True indeed! My problem is that I've got a booster and it stands out to compensate for the z-bar clutch. With the amount of space my booster takes up, it's impossible to switch to a dual bowl MC because the shock tower won't allow it. As it is, the single bowl MC almost touches the shock tower.

As far as I know, there's only one company that makes a power booster / dual MC setup for '65/'66 cars with manual clutch linkages... Master Power. They've got the booster/MC combo selling for $385 last time I checked. So it's not really so much $100 as it is $400 :) I suppose I'll have to drop the cash eventually... trying to find a place that'll do it for less though since I'm running out of money!
 

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Please, please... get a dual MC. I know from experience how it sucks when the fruit jar fails and you have no brakes. I was going to replace mine, but just hadn't gotten around to it (money issues at the time) and I was backing out of my garage which was on a hill. You guessed it. No brakes and I kept going backwards... right into my neighbors front lawn!

I couldn't imagine if they had gone out when I was driving around town with my kids in the mustang! I was extremely lucky it happened when it did.
 

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True indeed! My problem is that I've got a booster and it stands out to compensate for the z-bar clutch. With the amount of space my booster takes up, it's impossible to switch to a dual bowl MC because the shock tower won't allow it. As it is, the single bowl MC almost touches the shock tower.

As far as I know, there's only one company that makes a power booster / dual MC setup for '65/'66 cars with manual clutch linkages... Master Power. They've got the booster/MC combo selling for $385 last time I checked. So it's not really so much $100 as it is $400 :) I suppose I'll have to drop the cash eventually... trying to find a place that'll do it for less though since I'm running out of money!
Ouch! Tell you what, just make sure your parking brake works, they are supposed to be pretty horrible and barely able to get the car to stop, but it is better than nothing. You could downshift in an emergency to help slow down some.

I think the other thing people do is use a cable or hydraulic clutch, and a cheaper booster/master combo.

Don't panic or anything (not that you are), just enjoy the car, but I would put it on the to do list at some point. I would just check my fluid level a little more often and make sure my rubber lines are not dry rotted, or older than maybe , i dont know , 8 years?
 

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Oh yeah, I recognize that it has to be done - going to be a daily driver so everything needs to be in good shape! My rubber lines are in good condition, as are my brake lines, but I'd still like to switch over. My parking brake doesn't even hold the car on a slight incline either, which is another thing I need to go through. I had it tightened to where it would hold the car a few months ago, but then I couldn't actually pull out the brake because I wasn't strong enough! In between a rock and a hard place on that one.

The Z-bar clutch is staying - have heard questionable things about all 3 types of setup (mechanical, cable, and hydraulic). I prefer to stay with the simplicity of the mechanical setup on my [more or less] stock engine because I can forsee just about anything that would go wrong with it :) Plus, if I switched over to a cable or hydraulic setup, I'd still have to get a new booster / MC so I'd just be shooting myself in the foot financially.

I apologize for the thread hijack, but if anyone knows of any better solution for the booster / dual MC problem I'm having, PM me! I do need to switch it out by August.
 

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True indeed! My problem is that I've got a booster and it stands out to compensate for the z-bar clutch. With the amount of space my booster takes up, it's impossible to switch to a dual bowl MC because the shock tower won't allow it......."
Kelly, if the $400 system is too rich at the moment, I recommend getting the basic dual m/c from CJ or elsewhere with the bent lines, etc. and forget about a power brakes/boost system. If the brakes are in good condition and adjusted properly, a manual savefront disc.rear drums, right? If so it;s the 1974 Maverick master cylinder you will be buying.

I think this system will be plenty safe, and without the aggrevation of getting a power booster to fit.

Z.
 

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a dual master cylinder will NOT prevent a brake failure just because you have 2 separate containers of fluid. i had a front brake line failure and lost all brakes and one container of fluid was still full. i rolled into a parking lot,bought a plug and refilled the empty part of the master cylinder-got brakes and drove home only replacing the rusted thru front brake line to the left front wheel to restore my brakes so i had some brakes. no one has explained that so im not a believer of dual master cylinders. this happened about 6 years ago while towing a mustang to the paint shop, in traffic going 40 mph. talk about messing your britches- i almost did. wes
 

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a dual master cylinder will NOT prevent a brake failure just because you have 2 separate containers of fluid. i had a front brake line failure and lost all brakes and one container of fluid was still full..................only replacing the rusted thru front brake line to the left front wheel to restore my brakes so i had some brakes. no one has explained that so im not a believer of dual master cylinders. .........."
there are only two possibilities:

1) your brake system was plumbed improperly

or, more likely

2) your rear brakes weren't working at all before the leakage and you had been unknowingly relying on only the front ones.

Z.
 

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This same situation came up on the early bird forum a year or so ago and the problem was that there was not enough throw in the brake pedal to master connecting rod. The brake pedal had to be redrilled to get full travel. In normal operation hydraulic pressure from the rear moves the front piston. When you lose one end or the other then there is a mechanical push but it requires more pedal travel than normal. A factory install works fine or at least it does on my 68.
Good luck
 

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this was on a 92 caddi brhm rear wheel drive-all factory. i pumped and pumped with only 1 empty reservoir-no brakes but as soon as i added fluid and plugged the rusted line i had all brakes except left front where the bad line was.Go figure! wes
 

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It is NOT a myth about the dual MC, it's not that you should get one, it's
PS - I am sure someone will chime in saying they have driven a single master for 45 years, and they are fine. My response would be, a properly maintained system IS fine. I wouldn't run out to buy a dual setup. BUT, why on earth when these cars costs thousands upon thousands of dollars would someone not add redundancy to their brakes for $100?[/quote]

To respond to this quote.I will tell you a great story.Once while driving a 66 G.T. That I've had for years. I had all new and good condition brakes (Disc front with stock master) and brake lines . I was on a parkway ,beating on my car I admit it. The rear u joint failed I lost the driveshaft,it hit the rear brake line on it's way out.I lost the brakes. Try stopping your car from 75 mph or so, without being able to down shift and using the friggin parking brake handle. You should ponder that as you are driving to the autoparts store to buy a dual master. So up until that moment in my life I was perfectly content with single master cylinders.LOL. So if you are running a single master please RUN OUT AND BUY A DUAL !!!!!!. Sorry I yelled.

As far as the original posters problem,I wish he'd chime back in with how his system was plumbed, I'd bet it was done wrong. I always seperate my fronts from my rear.
 

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Kelly,

If one of the front rubber lines has dry rotted and is leaking, that could mean that the others are not far behind. In your case, if one of them seemed fine but went bad while driving, voila, you have no brakes.

It is NOT a myth about the dual MC, it's not that you should get one, it's that you need one. They are dirt cheap, CJ has the lines prebent. You can get a USA made, raybestos master cylinder new for under $80. Total is only $100. You can do it yourself too.

Although, I just read your signature (man, your car is awesome!), you are in the classic situation of having a manual tranny and wanting a dual master cylinder WITH power brakes. I think that gets trickier as the clutch can be in the way. I think there is a booster that works though.

PS - I am sure someone will chime in saying they have driven a single master for 45 years, and they are fine. My response would be, a properly maintained system IS fine. I wouldn't run out to buy a dual setup. BUT, why on earth when these cars costs thousands upon thousands of dollars would someone not add redundancy to their brakes for $100?
For the same reason that people who have "drivers" do not replace their oem pulley's......they are grenades waiting to explode (whereas the MC's if inspected & maintained are safe). At the bell portion of the stamped steel pulley's, weakness is inherient because of metal fatigue & can be verified by magnufluxing.....back in the 1990's I started seeing pulley failures on the Fords from the 60's....on one evening alone on the way home from a show I personally witnessed 1 65 mustang pulley shatter going through the hood and a 65 IIRR T-Bird's going through the radiator.
 

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or, more likely

2) your rear brakes weren't working at all before the leakage and you had been unknowingly relying on only the front ones.

Z.

This is my vote. There are two separate circuits. If one fails, the other will work, however, the pedal will feel like it's traveling most of the way to the floor before it starts to work. Also, the other system has to be working properly. My guess is the rear brakes are not adjusted properly and there's too much pedal travel. Therefore, you have no brakes.

Dave
 

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This is what happens if you do not change your fluid as a normal routine. Brake fluid is hygroscopic (attracts and sucks water out of the air) if fluid is not kept up, unworn parts of the bore will get contaminated, and when the other reservoir goes dry the the unworn contaminated portion of the bore gets used. Well because the unused bore is all contaminated, or eroded, the piston seal cannot seal. This will in turn not will allow the system to build up pressure when in this dangerous situation.

Oh if you wonder why is water bad. Water corrodes and lowers your boiling point of the fluid. If your fluid is no longer translucent, or black it needs changing.
 
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