Technical Help Identifying Master Cylinder

Hi All,
I recently inherited my dad's 1940 Ford 2 door sedan and I am trying to get it on the road again. I am having a brake issue. It has no brakes unless I pump the pedal about 5 times, then pretty good firm brakes, but goes away again the next time and right away. There are no leaks anywhere and the master is topped up with fluid. I am thinking the MC is shot and I should replace? The car has an aftermarket booster and MC under the floor. There are no markings but there are 3 bolts on the front of the booster and 2 bolts on the MC. Is this a GM or Vette master cylinder
and does anyone know a replacement or part number so I could buy locally?
Thanks,
Matt

 

I’d look into bleeding the brakes, may as well practice with what you have instead of buying another MC and doing it anyways

 

If they pump up hard the master is OK. Adjust the brakes if drum, then bleed all 4 corners. Should fix your issues.

 

yes, bleeding it first would be a good idea.

It's easier to ID master cylinders if you can take a picture of it from the top, which is hard to do when it's under the floor

 

Thanks for the replies. Disks in front and drums in back. I'll bleed them to see if that works. Just didnt feel like that. Pedal will go right to floor unless i pump them, the it goes right to floor again if I let up. Seemed like fluid getting by the MC but bleeding is cheap so I'll try that first. Thanks again, will post back results.

 

I also would suggest troubleshooting before R&R.
5 pumps for pedal THEN it's good is something doing strange stuff.
On disc, the square seal should retract the piston just enough to keep the pads from dragging.
On drum, fully released should also just barely clear the shoes. This one especially can cause problems. Also, there is a residual valve in the picture. These are designed to keep a small amount of pressure in the lines to avoid your problem. 2 pounds on disc, 10 pounds on drum. Make sure they are correct and working. Once the system is fully bled, let it sit for a few minutes. Then crack a bleeder and see if there is any pressure released. If you do not get a small spurt of solid fluid, something is wrong.
www.youtube.com/watch?v=DIVDjqniUX8

PS The MC could be bypassing, but it's almost always going to change the pedal feel depending on how fast you pump, and will also tend to bleed down if you pump up to a firm pedal, then relax SOME of the pressure.

 

Here is a pic from the top.

 

Adjust the rear brakes to you get a drag then bleed the system. If the rear brakes aren't adjusted properly it won't work with front disks. Ask me how I know !

 

That looks like a disc/drum MC (big/little).

 

Like I said adjust the brakes then bleed.

 

sounds like the car might have been sitting for a while....so it's likely that it needs some new rubber parts?

 

I think it is a mid '70's Ford M/C like this one from Speedway.

 

Also something to check. Does the car have residual pressure valves. The under the floor MC can gravity blead back. Do you know if the system ever worked correctly? Best of luck with your project

 

Bleed the MC only (preferably on the bench), but if on chassis make sure the MC is level.

Block off the MC outlets with plugs and if it holds pedal height, the MC is good.

Bleed the complete system.

Crimp the front brake hose(s) (gingerly) and if the pedal height holds the front circuit is good. Crimp the rear hose and if the pedal height is good (and shoe adjustment comes into play here), the rear circuit is holding pressure (or is frozen - pistons).

DISC/DRUM under the floor MC needs a #2 RPV on the DISC circuit and the rear drum circuit requires a #10 RPV.

Depending on how long the car has sat and if the brake fluid was never changed, it is full of water, trash and corrosion.

Ain't no getting around it.

​

What calipers are on it? If they are GM D154 (METRIC) (popular with CHI-CON off shores kits), they are low drag and require a step-bore MC or the ever popular CORVETTE STYLE.

 

To properly identify it you need to share the port thread sizes and the piston bore

 

Thank you all for the input, much appreciated. I was able to spend some time on it in the past few days. The DS rear was dragging and I could not spin it by hand when I got it off the ground. I backed off all 4 adjusters and it spins now. I couldnt get the hub off. Tried a 3 jaw puller but felt like it was going to snap one of the jaws so I gave that up for now. I'll get the proper puller and revisit that later.
I cleaned out the MC, added fresh fluid and completely bled out all 4 corners. Brakes work great now, including the DS rear that I backed off. Still going to get in there when I get a puller but for now should be enough to get to Ty Rods next weekend.

 

Thanks again for talking me out of RRing the MC and just bleeding it. The way it was acting seemed like it was done for. Saved me some $ and hassle. Thanks.

 

So glad you got it working, at least for now.
This may sound like a broken record, but the little temp guns are great for keeping an eye on suspect stuff. If you have one, keep it in the car for the run. Check the hub and brake temps to catch if it starts acting up, and to see what is normal. It will catch a low tire, a misfiring cylinder, a radiator with plugged tubes, a failing u-joint, anything that is hotter or cooler than normal.

 

Sorry about your Dad, he left you a good lookin 40!

 

Glad you got your brakes working and nice looking car. As for identification my first thought was AMC. It looks a lot like Raybestos MC36306.
They list a lot of applications. Here's a link;
https://www.raybestos.com/brake-master-cylinder-mc36306.html
Summit Racing sells them and lists a 1-1/8" bore.

 

Flathead Ford drum puller. Never use the 3 jaw.
https://www.ebay.com/itm/183765904026

 

The trouble with trying to ID a MC (or most any brake component - incl calipers) these days is that most are CHI-CON SLOPPY COPIES and are made to fit more applications than the vehicle dedicated OEM styles.