1959 Cadillac Deville dual master cylinder conversion brakes

[Bucky]

I know there are many archived articles regarding this, with most parts no longer optional....but what is the direct bolt on conversion or compatible year to replace with?
I know that caddy daddy has a conversion kit, but that is worse case scenario.
I'd like to preserve the stock look without the extended look of CPP.
THANKS IN ADVANCE

[Clewisiii]

I bought a 1962 2 zone set up to use in my 1961.

[Gabe Davis]

Hi Buck,

I did this conversion about 10 years ago when the parts were still available. That can be seen here:

http://forums.cadillaclasalleclub.org/index.php?topic=134898.msg295149#msg295149

The A1 Cardone 50-1117 is out of stock everywhere now. Mine seems to have developed a small leak in the master cylinder as I see fluid starting to slowly seep down the booster.

It is the 1968 booster and master with the drum/drum setup. I had to find some adapters to change the larger port sizes to the 1/4 lines on the car. I also added 10psi residual check valve to each line as I never was able to get absolute confirmation that the master had them built in. I have a feeling they were as there was no difference in the pedal once installed.

I have been looking into master cylinders and it appears that the AC Delco 18M1025 looks like it will bolt right up the 1968 booster. It is listed for a 1967 Cadillac. There are a couple of different versions that have ports on the other side and different line sizes.

https://www.rockauto.com/en/moreinfo.php?pk=496384&cc=1320185&pt=1836&jsn=17

I haven't pulled the trigger on it yet but will likely sometime this spring.

The boosters look to be the parts that are hard to find. If you can find something that is compatible with that master cylinder you could be in business and still look stock, depending on the booster.

[Dave Shepherd]

You can check for residual valves by inserting a 1/8 or so drill shank in the ports, you would feel light spring pressure feedback which indicates the valve is in place.

[Cadman-iac]

  Gabe,
I have a question, why do you want a residual pressure valve on a 4 drum system.
   The residual pressure valve is only used for disc brakes to maintain a minimum pressure on the calipers so that the pads stay in contact with the rotors. The rotors will warp slightly just from use, which is normal, but because of this, without the residual pressure valve, it would cause the pads to spread and the caliper pistons to retract, and this then causes a low pedal the first time you apply the brakes. Once you release and reapply the brakes, your pedal will feel normal again.
Likewise, on a drum system, if you install a residual pressure valve in the line, then your shoes will not retract like they're supposed to, causing them to drag and overheat. The only thing that retracts the brake shoes are the return springs. They don't have enough force to overcome the pressure a valve would maintain in the lines.
I'm no expert, but in my opinion, I wouldn't use any residual pressure valve on a drum system. That's just asking for trouble.

  Rick

[Gabe Davis]

Hi Rick,

The post here and the messages afterward explains why I did it:

https://forums.cadillaclasalleclub.org/index.php?msg=245225

Basically it seems to be a good thing to have a little pressure in the lines to give the pedal a "head start", as Bill described it, so it is not as low when pressing it down.

There are different valves with different pressures for drums and discs. And in some cases the valves are integral to the master cylinder.

[Cadman-iac]

Hi Gabe,

I guess I'm just old school. I've never heard of using a residual pressure valve on drum brakes before, but yes, it's right there in black and white.
This theory must be like what we called "the new math" when I was in school, ain't never seen or heard of it, but it's in the book, lol!!
I guess if they say you can do it, and even suggest it, there must be a reason for it.
I still think it goes against regular convention, but then I'm just a couple years younger than my car, so I could be loosing it now.
I would definitely be interested to hear how it works out for you though. Keep us posted on what happens if you don't mind.
  Thanks for the edjamakayshun!

  Rick

P.S.  What I've always been taught is to keep the shoes adjusted properly to minimize the clearance between them and the drum, which in turn keeps the pedal from traveling too far.

P.P.S. Another thing if you are using a pressure valve on your drum brakes is that if you have any weak return springs, your shoes will still basically be applied, resulting in warped drums if you don't catch it in time.

[Roger Zimmermann]

On drum brakes, a small residual pressure is a must. Without that, the lips from the seals into the cylinders will not get pushed against the wall and they will slowly leak.

[Cadman-iac]

  I stand corrected. I've been looking into the use of a residual pressure valve on a drum brake system and found this on the ECI, or Engineered Components Inc. website, explaining why you would want to use one.

10 PSI Valves - These valves are used in a drum brake system to prevent air from being ingested into the hydraulic system when you release the brake pedal. Typical wheel cylinder seals only seal when there is pressure behind them. Rapid release of the brake pedal creates a vacuum in the system which causes the seals to relax and air is ingested into the wheel cylinders. Maintaining 10 PSI in the system at all times prevents this. Some disc/drum master cylinders have 10 PSI residual pressure valves installed internally, some don't. If you're not sure, call us and we can tell you how to check. Also, some new style wheel cylinders have cup expanders which negate the need for the residual pressure valve. Either way, if you are not sure whether you have one or not, put one in. They are not cumulative and it won't hurt anything if you have two. Don't worry about brake drag, it takes roughly 75 PSI to overcome the return springs.

  I was unaware that it took so much pressure to overcome the return springs on drum brakes. I had always thought that any remaining pressure was bad and would cause the shoes to drag.
They also mention the formed spring ends, or the use of fitted cup expanders to prevent any leakage of fluid or the possibility of air entering the wheel cylinders.
All of the cylinders that I've used have had one or the other designs already in them, or the wheel cylinder kit had it, so I never thought about the possibility of air entering around the piston cups.
To be honest, I hadn't even paid any attention to what was in the original wheel cylinders on my 56. I knew that they would have to be either rebuilt or replaced, so I expected the new cylinders or the kits to have one or the other design of springs/expanders incorporated into it.

  I'm into the 64 through 66 Chevrolet trucks, and they originally had a single master cylinder with all drum brakes. No residual pressure valve was used. When I converted to a dual master cylinder, but retained the 4 drum system, I also added a stock metering block with a warning switch in it. But even those don't have any pressure valve in them.
Once I converted to disc brakes, I used a stock proportioning valve from a newer truck, and the only thing it had was a valve for the disc half.

I was going to use the same setup for my Cadillac if I converted it to discs, but due to other considerations, I opted to go with the 4 drum system.

I'm glad I saw this thread, as I hadn't known it was necessary to use the residual pressure valves with drum brakes. I think I'll be getting a pair of them now.
Thanks to all who have argued the point for this.

  Rick

[Gabe Davis]

I ended up going with the Wilwood 260-13707 check valves. One in each circuit. Hit them with a bit of black paint so they aren't quite so obvious.

https://www.summitracing.com/parts/wil-260-13707

[Roger Zimmermann]

Rick, the residual check valve is build into the master cylinder on the '56 cars, no matter if its a Bendix or Delco Moraine master cylinder.

[Cadman-iac]

Rick, the residual check valve is build into the master cylinder on the '56 cars, no matter if its a Bendix or Delco Moraine master cylinder.

Hi Roger,
  Yes, that's true, (a fact that I had forgotten apparently), but I'm converting it to a dual master cylinder with a Hydro-boost unit mounted in the original booster location. This keeps the overall length of the unit just about the same as the original one.
  Since I had to put everything on hold due to health problems, I haven't been able to finish it yet though.
 
On the topic of the residual pressure valve, I dug out a book I got back when I was still in school, printed in 1970, and read through the brake system section. In it they mention that you want to have between 8 and 16 PSI on the system to prevent air from being drawn in around the piston cups.
I admit that I've forgotten all about this, and have been under the false assumption that any pressure remaining is detrimental to the operation of the system.
Although in my defense, better designed springs with formed ends that fit into the piston cups do prevent this problem, negating the need for a residual pressure, and this had been what I was basing my argument on. I was wrong.
But it seems that the popular and prudent thing to do is to install a residual pressure valve in the system.
So it is possible to teach an old dog new tricks.

Thanks, Rick

[Bucky]

Good information to know... keeping this for my records. However, any assistance or information regarding an immediate concern - compatible dual master cylinder upgrades for a 1959 - would be greatly appreciated.
Hard to believe people are still driving these cars with a single master.
If there is no other option, would I have to modify anything to install the "bulkier" CPP, POL..etc.? Running all drums....thanks!

[Cadman-iac]

  Bucky,

I'm not sure what the mounting pattern is on your master cylinder, not familiar with that year. But I do know that GM had used the same pattern for most vehicles through the 60's and up. That's how I was able to convert my 64, 65, and 66 trucks to a dual master cylinder. I did the first one using a master cylinder from a 67 truck, because I was just doing the master, not adding discs.
But if you can, look at a master cylinder for any GM car or truck from 66 to 70 that still had 4 wheel drum brakes and compare the mounting flanges,but also check the depth of the piston where the rod pushes it. You may have to look at one's for both power and manual brakes to find one that works.
It is possible to get there from here, it just requires some work.
I would also suggest that you locate and use the metering block used with the trucks with all drum brakes. The reason why is because it will allow you to wire in a warning light, but mainly because it will block off either line in the case that you have a leak. These are small, and  a simple design. Just using the dual master cylinder alone doesn't work any different than the single master cylinder.
It's a bit more plumbing, but well worth the effort.

Rick

[35-709]

1962 was the first year for a dual master system in Cadillacs.  I would start there looking for a bolt in (or nearly so) installation.  1962 dual masters are no longer available new from what I understand, so the additional problem will be finding that particular year and making sure it is rebuildable.  I would look right up through 1964 as being your best bet. 

[76eldo]

So a 62-64 master will bolt onto the existing 1960
Booster ?