Brake Master Cylinder Rebuild on a 1948 Chrysler Royal Question

[Tom Skinner]

Gents,

Having owned 1948 Chryslers for 50+ years I have never rebuilt, or replaced a Brake Master Cylinder. I have 3 Questions:

1. Does the Master Cylinder need to be out of the car to rebuild it, (The Serv. Manual speaks to this) or is there room to replace its inner parts with it in the car.

2. Would you rebuild it, or replace it if you had parts for either (a re-build or replacement).

3. Go over the part about replacing the inner parts with it in place, as opposed to just pulling the floor pan and whole MC out and having to press out the Pin etc.

It would seem to me if it could be re-built in place it would save a lot of labor.

Thanks in advance for any feedback.

Tom

 

 

[desoto1939]

Tom: You state that you have owned the car for over 50 years and have not done any maintenance or rebuilt the MC.  Yes it is not the type of repair work that we do every year like an oil change or other maintenance.

 

I do assume that you do check the fluid level in the MC and that you might bleed the entire brake system every few years. But you have never had the MC apart or inspected during its useful life since you have owned the car.

 

I would suggest that you at least get a NOS unit to have as a spare and or a repair kit. Yes pushing the pin out might be a pain in the butt, but if you learn how to do the job then you will know the internal condition of your MC.

 

If you do not feel confident in doing the work then suggest that you find a mechanic that can do the work for you and would try to get it done now during the winter months.

 

I am a shade tree mechanic not a certified mechanic but curretly rebuilding a distributor for my 39 Desoto.  Yes it is scary doing something that you do not have alot of experience with but if you ask alot of questions and do some research you will be surprise at what you can accomplish.

 

remember that these antique cars are a hobby and that they do not need to be fixed in one day. It might take several days to complete the project and that is the beauty of the project. When you get stumped you can ask for help and diagnosis the issue.

 

Rich Hartung

desoto1939@aol.com  

 

 

 

[Tom Skinner]

Rich,

I have owned 1948 Chryslers (see above - plural a s at the end of Chrysler for 50 years) I always bled my brakes every other year or so. I just replaced all of my Wheel Cylinders and Shoes and adjusted them to pretty good satisfaction, however, the slam the brakes on skid test doesn't work unless I pump the Brake Pedal and then it comes up hard and firm but doesn't skid. I believe the MC is original on my present Chrysler and may need rebuilding or replacing. I have good brakes now, however I feel they should/could be better.

That being said thanks for your input, I can and will finish the job myself as I am still stout enough, I just need some technical input as to where to start and a little step by step advice as to what I may need to look out for that might trip me up.

Tom

[9 foot box]

   I put a kit in my 49 P15 without removing the MC. I honed it with brake fluid as a wetting agent and cross hatched the length of the cylinder and installed the kit from the rear. The push rod and boot were removed for visual inspection of any blemishes by using a light at the forward port before assembly. 

[Roofus]

I dismantled my MC for exchange with a new one, I was able to easily shift the axis of the pedal and take the MC out from below without dismantling the floor, but I may have been lucky.

On this occasion, I noticed that the valve system at the end of the spring which is mentioned in the manual is no longer installed ...

Edited February 13 by Roofus

[desoto1939]

22 hours ago, Tom Skinner said:

Rich,

I have owned 1948 Chryslers (see above - plural a s at the end of Chrysler for 50 years) I always bled my brakes every other year or so. I just replaced all of my Wheel Cylinders and Shoes and adjusted them to pretty good satisfaction, however, the slam the brakes on skid test doesn't work unless I pump the Brake Pedal and then it comes up hard and firm but doesn't skid. I believe the MC is original on my present Chrysler and may need rebuilding or replacing. I have good brakes now, however I feel they should/could be better.

That being said thanks for your input, I can and will finish the job myself as I am still stout enough, I just need some technical input as to where to start and a little step by step advice as to what I may need to look out for that might trip me up.

Tom

Tom:  wih the 1948 Chrysler you have the Lockheed brake system that utilizes the eccentric pins to move the shoes inward and down and outward.  If you have anyone that might have the Factory Miller MT19 Brake setup gage tool then try to borrow that tool since it can set the shoes up to factory specification or even borrow the Ammco 1750 brake gage or even purchase from Keith the tool that he made to adjust the individual shoes on each axle.

 

Since you will have the two wheel cylinder setup you will also start your bleeding at the bottom cylinder and then bleed the top wheel cylinder.

 

If your eccentric pins have the arrows stamped into the ends then rotate the pins so that the arrows point towards each other. You will have to loosen then castle nut on the back of the backing plate first.  On each pin there should be a flat spot to accept an open end wrench might be 9/16 or 1/2 I do not remember.

You will also need a set of feller gages to help gap the shoes at the toe and heel.

 

After getting each shoe adjusted properly then hold the eccentric pin on the outside with your open end wrench. Use a torque wrench and torque the rear castle nut to around 75 foot lbs. Hold the pin from rotating via the use of the open end wrench.

 

Install the drum and make any fine adjustments with the top half moon adjuster.

 

read and reread the factory service manual on the brakes for your car and fully understand the process. It takes some time on the first drum but you will get quicker as you do each drum.

 

On my 39 Desoto I only have a single wheel cylinder and on my brakes the rear shoes on both the front and rears have the short lining shoe installed on the rear and the long lining on the front for each brake.  This was the factory setup since we used steped wheel cylinder pistons.

 

Hope this might help.

 

Rich Hartung

desoto1939@aol.com 

[Tom Skinner]

Rich,

I have done all of the above in your previous post. I use the homemade tool to adjust the shoes with the feeler gauge .006 around Heel and Toe.

I also checked shoe wear with chalk on test runs and removed the drums several times to re-adjust Heel Toe to satisfaction. My only thought is shouldn't

the tires actually skid when slamming the brakes on without one pumping action? That my friend is why I am questioning the strength of my Master Cylinder.

The advice I seek here from another old Mopar War Horse like myself is: What to disconnect first to start the MC Re-Build or replacement.

Roofus came close with his description of shifting the axis of the pedal etc.. I will wait a week or so for a seasoned explanation - sort of step by step, or just plow ahead on my own next week. I even have the bushings - if needed to replace on the MC Pin so I don't lack parts just some simple start finish tips to avoid the usual stupid stuff that may pop up as is usually the case when working on our old buses. Not being so young my bark is getting thin so I have to wear leather gloves so as not to cut myself. LOL.

The Ammco 1750 and the MT19 Tools are best to own but not necessary if using the tool I used, (Which I will admit takes several tries) because the homemade tool is not as accurate. All in all having done Shoe and Wheel Cylinder brake jobs on old Chryslers over the years I sort of have a knack for it. Thank you for your input. By the Way the Cam Nut is 9/16" as you said above The Anchor Bolts are 7/8" Wrench. The real problem I see is the old brake lines going into the back of the MC need PB Blaster for sure as well 

as everything looking kind of crusty so as not to break anything - especially brake lines.

Tom

 

 

[Tom Skinner]

OK Gents here's the tips:

I went on the AACA Thread to get this information. I will mark this Thread as solved afterwards. 

In order to remove the Master Cylinder there is a Pin/Rod at the front of the MC. Use a 13/16" Open Wrench to push the Retaining Clips off the Pin Ends in order to remove the Pedals. If need be use JB Blaster to loosen every Bolt up to and including the 2 Brake Lines coming out of the back of the MC. One Line supplies the front Brakes the other the Rear Brakes. Have a Drain Pan to catch the Brake Fluid after removing the Lines or the Front Push Rod. Remove the Bolts and Replace the MC. by reversing the steps.

The Service Manual speaks to this but to have the tips to remove the Retaining Clips without them spinning and staying on the Pin/Rod is very helpful. Re-install the Pin/Rod with a Mash Hammer if a Press isn't available (LOL) be careful not to Monk up the Pin ends. There is a MC Bleeder Tool (It Looks like a syringe) to Bleed the MC before bleeding the rest of the System. So there it is Easy Peasy. I was just looking for some simple Tips. These could benefit others that would like to replace their Master Cylinders without any reservations as to skill set. I know Rich likes to Push The Ammco 1750 and MT19 Tools for adjusting Brake Shoes but they really aren't necessary unless you have $600 or more to throw away for a tool you may only use once or twice in your life. In addition to that you would be upside down real fast with your old Mopar paying someone else to monkey with it. Unless the Mechanic is 60 years old or better and know what he is doing with these old Shoe Brakes or a Truck Mechanic with Shoe experience. 

For now I am holding my own enjoying still working on and mastering every little thing my Chrysler throws at me, it is a tremendous privilege to continue be able to do so.

Tom