Screw in front master cylinder reservoir?

[Bad B-rad]

I was tinkering with my 69 power drum brake car yesterday, and I went to add brake fluid and noticed a Philipps screw inserted into a hole in the front reservoir(closest to engine, in the part where you add the fluid).
Is this normal?
I have only had manual drum brakes(duel reservoir and single) in the past, so this is my first power drum brake master cylinder, but it looks kinda off.
I will try and post a photo of it later, the screw is inserted in to the hole/port with the raised boss cast into it, it looks to have three total holes/ ports(two open and the screw in one)
Thanks.

[A383Wing]

that doesn't sound right.....sounds like someone was trying a backyard fix to cut the fluid flow to the brakes....kinda like a proportioning valve.....

[BLK 68 R/T]

If probably the retaining screw for the piston.

[Bad B-rad]

having hard time posting photo, I can email photo to someone if they can post for me.


I had thought maybe someone blew a brake line or had leaking wheel cylinder and maybe that was their fix??

[birdsandbees]

 

[Bad B-rad]

Big thanks to birdsandbees!!!


As you can see the screw almost looks like it has a washer under it, but I think that is cast into the bottom.
I only had a few minutes to mess with it before I had a job to do.
I got the #'s 383 running and tuned up nice, so next I need to make the brakes work so I can test drive my baby!!!!!

[BLK 68 R/T]

Never mind on my comment above  didn't realize it was on the inside

[birdsandbees]

Yah, I almost posted this pic for him !

[Bad B-rad]

So am I correct in thinking that the screw should not be there?
Was someone trying to remove fluid from the master cylinder with out getting air into system?(system was empty when I got the car)
I am just grasping at straws.

[BLK 68 R/T]

Yah, I almost posted this pic for him !

That's the one I was thinking of. Figured maybe someone replaced the bolt with a Phillips head machine screw or something.

I would not use that master cylinder 

[Bad B-rad]

So the plot thickens.......
I tried to pump up the brakes a bit, and they go in a little hard, but petal will not return on its own power.
So I pumped it and pulled it back up a few times, just to see if I unstick something, and it had no effect.
So I remove the screw, and it is not a screw, it is a Philips head port plug!!!?
It looked like a screw when it was installed, but when I removed it, it has maybe 5/16 of an inch of threads, then about 3/8 an inch of a "Dowel" on the end of it.
Again looks like it is designed to plug up a port in hydraulic systems???

So I am certain I will be getting a new master, but I still wonder what this is all about.
In all of my previous duel circuit Mopar brake systems, drum brake master cylinders had the bolt down cap.
Disc had the bail arms.

I have a 67 Charger power drum master in my shop attic, and that and the 68 Coronet masters I have are both the bolt down tops.
I am not Mark Worman, or Tony D'Agostino, I do not know everything Mopar ever did, but I have been playing with them for a while.
So what is going on here?
Ultimately it really wont matter, as I will be replacing this master, but just trying to get to the bottom of this, LOL.
My power drum brake master, has bail arms,not bolt down top,(and the two reservoirs look the same size) and it looks as if this port that the screw was in belongs in the hole?

Anyone have a power drum brake master with bail arms, and this third "hole/port" in front reservoir? and if so is it plugged or open?
Thanks, again, it is not the end of the world if I cant get an answer,I just want to know.

[Bad B-rad]

And one more thing, the power booster on my 69 Charger, is also different then the booster on the 67, and 68 setups I have.(the masters that have bold down cap).

I am gonna guess the difference maybe the midland and bendix,mfg??
So could that be the reason the masters are different(one bendix, others midland?) and are there any"rules" as to what cars got what?
As far as WHERE they were built,or  WHEN they were built?
thanks.

[sccachallenger]

If probably the retaining screw for the piston.

I think this is correct, I remember rebuilding one back in the '70s and kit came with this screw.
Maybe look up a rebuild kit for the master and see what it comes with.

[green69rt]

If probably the retaining screw for the piston.

I think this is correct, I remember rebuilding one back in the '70s and kit came with this screw.
Maybe look up a rebuild kit for the master and see what it comes with.

Here's a look inside my Disc/drum MC.  I got it from Dr Diff so probably not correct.  Just for info.

Amazing the details that come up on this forum!

[Bad B-rad]

What does your booster look like?
  I will take photos of the one on my 69 power drum, vs 68 power drum, and post after I get back from the doctors.

[gtx6970]

Cant say Ive ever see that before.

I thought the question was about the one in the side of the casting ( that ones piston retainer )

[Bad B-rad]

https://www.napaonline.com/en/p/UBP474




Here is the screw/plug in a rebuild kit photo.
It is the screw/port by the "A" in napa
If you + you can make the pic larger, it is the first one on the left side, you can see the end of the screw has the thin, dowel like end.

[BLK 68 R/T]

Did some digging and came up with this thread. It shows in reply #7 there is no piston retainer that I can see in the photos except for the small tab on the very back of the master cylinder. I think the rebuild kit is the same one as the napa link you posted. Going by what I can see from yours, my guess is that screw is the piston retainer on yours. Maybe different sn ranges or batch lots just used a different retainer method or something like that 

If you are planning on replacing/rebuilding yours or are just super curious, you could see how yours comes apart and whether or not the guts will come out without removing that screw.

http://www.dodgecharger.com/forum/index.php?topic=121612.0

[Bad B-rad]

I am more just super curious and I was hoping I could just throw some fluid in it and bleed the system, and I would get the brakes working well enough to drive the car to my buddies body shop, 2 miles away from my place, and I can start on the 1/4 replacement.

I like to learn, and I had thought at first this "Screw" was just something that had been slapped in to the port as a backyard mechanic way of cutting down flow/volume, or to "Plug" the system.


Also according to Dr.Diff, I have the "Good" bendex booster, he said they put them on drum AND disc cars, and my master has the bail arms not the bolt down top.

I will probably put on power disc brakes, and then I will check out mine.
The funny thing is, a rebuild kit is $30, or a re-man master is $35?(with no core charge)
WTF!!!!!