1950 Ford Custom Brake Master Cylinder
 

Is the stock OEM 1950 master cylinder reservoir "pressurized" during brake application or pedal return?


A little history on the issue and reason for the question.


I had a soft pedal and checked the reservoir (once I got the cap off which I believe has been on the car 75 years too) which was low; no apparent leaks. This is the second time for a soft pedal in the last two years. The cap and gasket were very dirty.


What I think was happening is a little fluid was escaping from the master cylinder cap each brake actuation and the residual was moving around under the car as it was driven. No static leaks other than oil that probably had some brake fluid in it looking back...




I applied the brakes a few times; I had a soft pedal due to low fluid and after adding fluid the pedal firmed up nicely.


My question is: Is the master cylinder reservoir pressurized? Because while I was applying the brakes with the cap off fluid would "squirt up" an inch or so in the reservoir which makes me think the cap is holding pressure but probably not much but enough to make the cap leak if the seal is bad.


Pretty sure the cap and seal are decades old. I cleaned the threads out they were very dirty and cleaned the gasket area which was caked with gunk. I reinstalled the gasket and added an o ring to seal it which seemed to work very well.


I will bleed the brakes just to make sure there is no air in the system and change out the fluid.


THANKS IN ADVANCE for any thoughts on this.

Re: 1950 Ford Custom Brake Master Cylinder
 

No, the master cylinder chamber is not pressurized. The "squirt" that you see is the pressurized fluid outboard of the master cylinder, the brake lines and wheel cylinders, squirting out the bypass port when the brake pedal is released. In addition, the master cylinder caps and gasket are vented to maintain atmospheric pressure. I just looked at a few links and I liked this one for graphic explanation.

https://www.youtube.com/watch?v=rcvhntRbTb4

Re: 1950 Ford Custom Brake Master Cylinder
 

Thanks for the link to a really good video on the operation.


So the return bypass fluid would increase the pressure in the reservoir but the cap it is vented so it can't build up; makes sense.


I will keep checking the fluid level and see what happens with the new seal on the cap...

Re: 1950 Ford Custom Brake Master Cylinder
 

When is the last time you did an R and R on the brake system? If the cap and seal is decades old I suspect the system is decades old. It's time to replace all the components and flush the lines of old fluid.

Re: 1950 Ford Custom Brake Master Cylinder
 

Yes that's correct the cap vent prevents pressure buildup from the pressurized brake fluid squirts out the bypass hole.

Re: 1950 Ford Custom Brake Master Cylinder
 

I'm with TJ. I love fresh brakes.

Re: 1950 Ford Custom Brake Master Cylinder
 

Yes, every two or three years, you should flush the whole system. Look into your master cylinder reservoir and when it starts looking brown, it's time to do it.

Re: 1950 Ford Custom Brake Master Cylinder
 

Well that's a good question...
Best answer is: A full system fluid change will be done soon.
Thoughts of changing over to a dual master cylinder is on the list too... just need to look at all the modifications needed for that before opening that can o worms...

Re: 1950 Ford Custom Brake Master Cylinder
 

I would definitely flush all the old brake fluid out. On a vehicle that is driven regularly you are supposed to replace the fluid every two-years because the brake fluid attracts moisture. I was a fleet mechanic for 30-years. What we did was drain the master cylinder and fill it with new fluid. Then as we were changing the brakes we would open up the cylinder on that wheel and let the old fluid gravity drain out while we were changing the lining. I would look at the rear of that master cylinder and make sure it's not leaking from the rear seal. It's normal for the brake fluid to squirt up as the pedal returns, that's just the fluid returning back to the resevoir, If you have a bad gasket it can slosh out and empty your resevoir You want to really keep an eye on single systems, you hace no emergency secondary resevoir to stop it with like modern cars There's nothing wrong with a single systems "if" they are maintain.

Re: 1950 Ford Custom Brake Master Cylinder
 

Ok so found the leak! Pretty sure the fluid is leaking from the master cylinder which is no surprise really. The "oil" under the car was in fact part brake fluid probably coming from the push rod. I haven't removed all the mud shield to verify but it will be removed when the Master cylinder is replaced.


After reading the replies here I decided to replace the entire system minus the hard lines. I purchased the ShoeBox Central "kit" with all the wheel cylinders, hoses, linings and hardware so the car should be good to go brake wise for a while.


ANY TIPS on a full system replacement? My plan is to open all the lines bleed all the old fluid out cap them off to prevent contamination, replace the master cylinder and each wheel hose, cylinder linings and hardware. THEN bleed the entire system with the new master cylinder installed...


Any issues you guys can see? Different sequence maybe?


TIA

Re: 1950 Ford Custom Brake Master Cylinder
 

Bleed the brake lines after you install the new master. This will give you nice clean fluid throughout.

I like to use 1-1/2 turns of yellow teflon tape, wrapped CW, which is good with hydrocarbons.

Look at the new wheel cylinders carefully and keep the old until you know they are working correctly. Some of the "new" wheel cylinders have issues with bleeder drilling and cups being too short ...

https://www.fordbarn.com/forum/showt...rake&showall=1

Re: 1950 Ford Custom Brake Master Cylinder
 

Your plan looks sound to me.

One thing I recommend to make your fill/flush easier is the Motive Products power bleeder. https://www.motiveproducts.com/collections/all

Super nice for a one-person job. Make sure you get the correct adapter for our master cylinders. I also like the quick release fittings connector. PM if you have questions.

Ken

Re: 1950 Ford Custom Brake Master Cylinder
 

I just bought and used the attached which functions based on low pressure from a venturi. I usually use a vacuum pump but have also pressure bled. This tool I like the best.

https://www.amazon.com/dp/B0CDV3D5ZS

Re: 1950 Ford Custom Brake Master Cylinder
 

Ok so probably NOT MY LAST QUESTION...


With the planned replacement of the master cylinder, all flexible brake hoses and wheel cylinders what would be the brake fluid of choice?


DOT3 seems to be the front runner based on what I have read so far...

Re: 1950 Ford Custom Brake Master Cylinder
 

I like DOT4 with it's higher boiling point. Be ready for the DOT5 comments :-)

Re: 1950 Ford Custom Brake Master Cylinder
 

Actually, this thread got me thinking and I did a little research. I used to be a "DOT4 guy", but after a little digging, I'm starting to lean towards DOT3. The main advantage of DOT4 fluid is a higher boiling point (around 440° F as I recall). However, its downside is that it picks up moisture more quickly than DOT3. The boiling point of DOT3 is 407°. The way these cars are used and the very nature of the brake systems tells me that we will probably never need those extra 30°.

As things stand now, I think I'd rather have the reduced moisture pickup and retention than the extra protection offered for "heavier vehicles and trailer pulling".

Speaking of moisture in brake fluid, I purchased a tester about 15 years ago that will determine the moisture content of your DOT3 or DOT4 brake fluid. I use this every year to check my vehicles. I have found that for collector cars stored under favorable conditions, DOT4 brake fluid doesn't reach a minimum moisture level until after 9 years. If DOT3 extends that even a year or two, I'll start using it, because I don't use my old cars to pull trailers and I hate changing brake fluid.

I put DOT5 in a '68 Corvette I owned years ago. After I got it in and bled, it was great, but not near worth the effort.

Re: 1950 Ford Custom Brake Master Cylinder
 

Thanks, I didn't know about the longer service life for DOT 3. I have motorcycles that specify DOT 4 so I'll be staying with DOT 4.

I used DOT 5 in my '40 decades ago but it never felt solid regardless of multiple bleedings. I lived with it for a while and then flushed with DOT 3 at that time.

Now I'll see what my unused tester that I bought a few years ago :-) tells me tomorrow.

Re: 1950 Ford Custom Brake Master Cylinder
 

Good info guys. I've always been a DOT 3 guy, mostly because we have used it for eons. I knew some guys that got on the DOT 5 bandwagon and regretted it, mostly because of the soft pedal. Just never went to DOT 4.

I'm amazed to hear that some conventional fluids could laxt that long, even though I have often been delinquent in flushing. Will be interesting to see your results.

Re: 1950 Ford Custom Brake Master Cylinder
 

Thanks for the reassurance 4 has to be better than 3 right and then there is 5

DOT 3 for the win... Parts arrive today so should be fun after watching a few videos on the replacement well not sure fun was any of the words ised to describe the process

Re: 1950 Ford Custom Brake Master Cylinder
 

The process is tedious, but rewarding. I recently replaced the master cylinder on my '50 convertible, which is made much more difficult by the additional X frame.

The YouTube video by Chris at Shoebox Ford is a very good guide. Make sure you take pictures of everything you take apart to help you get them back together. There are lots of washers and spacers in place that may be glossed over in the video. Avoid taking any shortcuts.

If you hit any snags, I'll be glad to help you.

Ken

Re: 1950 Ford Custom Brake Master Cylinder
 

Hi, the video is good but.... I did mine two years ago. Order new pedal bumpers while you are at it. The inner fender bolts came off by thorough cleaning, blaster penetrating oil, and some heat. I have carpeted floors and there was no way I was going to pull that carpet back to reach the bolt heads. Most important, the Shoebox Central M/C casting needed to be trimmed so the brake pedal would clear. I found this out the hard way as I had already put the new M/C in. Oh, and Ace hardware had the new snap ring. Hope this helps. It's a pain, especially on your back and I'm not young. :)

Re: 1950 Ford Custom Brake Master Cylinder
 

x2 on the new pedal bumpers. You need to have the pedals off to properly install them and this is your opportunity. Make sure you have proper snap ring pliers to remove that snap ring from the brake pedal shaft. I used the pair recommended by Chris.

Here is a source of the pedal bumpers if you don't have them: https://shoebox-central.com/1949-195...rubber-bumpers

Ken

Re: 1950 Ford Custom Brake Master Cylinder
 

Thanks guys for the info and offers of help; I hope all the washers are there when I get it disassembled. I did order the pedal bumpers and rubber seals.
More fun to be had!!


I found and watched this video too; seems like a pretty good breakdown of the parts involved.


https://youtu.be/bdHoIpENbfA?si=BYwhg3k0mIOIQDUO

Re: 1950 Ford Custom Brake Master Cylinder
 

OK SOOOOOOOO....
After watching a few videos on the brake master cylinder and then looking at how the piston and seals are inserted HOW can there NOT BE a rebuild kit with seals that can be changed without removing the cylinder?

One C-clip ring a retaining washer holds the piston in.

Thinking it would/should/could be easy enough to pull the piston out and replace the seals.

I must be missing something...

Re: 1950 Ford Custom Brake Master Cylinder
 

OK so apparently there are several options to rebuild a master cylinder just had to get the search words right (rebuild kit) vs seals or piston etc.

Anyone have experience with any of the options from Dennis Carpenter Classoc Industries, Summit pr Speedway?

TIA

Re: 1950 Ford Custom Brake Master Cylinder
 

Last year I installed an o-l-d MC repair kit in my '50 Crestliner - while it was in the car. Worked fine. I probably had the kit in my parts bag for 15-20 years.

Then, on my '50 Convertible I installed a new MC repair kit (purchased last year from one of the normal suppliers) and the MC leaked worse than before. I don't know if the problem was because of the condition of the MC or if the new kits are not of the same quality as the old ones. I then installed a new MC and all is well.

It is not an easy task to install the repair kit without removing the MC, but somewhat easier than the total replacement. I would not be afraid to continue with the total replacement.

Ken

Re: 1950 Ford Custom Brake Master Cylinder
 

THIS is why Ford Barn is awesome!! Figured it was hard to do needing to dissemble much of the same items as replacing the MC so THANKS. I plan to replace the MC and will get a rebuild kit for the old MC keeping it as a spare.

Re: 1950 Ford Custom Brake Master Cylinder
 

Replaced the MC on Saturday and the process was pretty painless.


Having access to a full height car lift is the key IMO.


Took about 3 hours total being very careful and deliberate but I spent another two hours greasing all the fittings I could find and looking at other stuff... ALWAYS more stuff to do.

The shield was the only real issue due to three of the self tapping screws being replaced with nuts/bolts; so I needed a helping hand.


Once the shield was loose the clutch pedal bolt was easy to remove, I had already removed the foot pedals so I could remove and install the new bumpers.


I decided to loosen all the bolts up before removing them and I think it helped keep the process "organized".

Once everything was loose it became obvious the grease fitting on the through shaft had to be removed in order to have enough clearance to slide it all the way out. Once removed and the others removed the through shaft slid right out.


Install was just as easy the only real problem was tightening the banjo bolt without rotating the brake line block.


Bled the brakes until fresh clear fluid bled out of each. IT WAS DIRTY!!!


Now I have a FIRM brake pedal and the car tracks straight when brakes are applied (straighter than before) so must have had some air or just bad/worn out/ contaminated brake fluid near the wheel cylinders.


Clutch works fine no issues with the new bumpers installed the "old ones" were pretty new looking not compressed so no adjustment was needed.


Easy Peasy really; the only suggestion would be to get or make new felt washers as mine were compressed and a little oil soaked. FWIW little soap and water and pulling apart the fibers helped restore their shape and hopefully better do their job.


AND the "wavy washers" thrust washers/ anti rattle washer one of the videos described were not installed my car, it has washers that are stamped with a raised inner area so that's what went back on...

Re: 1950 Ford Custom Brake Master Cylinder
 

Congratulations! It is satisfying when you can do a job like this yourself. Having the reliable brakes is the real payoff. I'm happy that you took the job on and handled it.

I agree with you about the lift - had to do mine laying flat on my back.

Ken

Re: 1950 Ford Custom Brake Master Cylinder
 

Great , love happy endings!