Military-Vehicles: [MV] '41 Dodge Master Cylinder -Reply

[MV] '41 Dodge Master Cylinder -Reply

U. N. Owen (
Wed, 29 Oct 1997 15:31:40 -0600

On 10/29/97, at 02:09 PM, WIDD-James(MAJ) Rice (WIDD-James(MAJ) Rice)

>Your situation sounds a great deal the same as on my 43 GPW. I also
>blasted mine to clean it up and also found the holes to be clogged. A
>small drill bit, twirled between the index finger and thumb will usually
>open the hole up with a moderate amount of pressure.
>As for the cone shaped apparatus, that is the piston which "should"
>move forward when pressed by the rod connected to the pedal. Mine
>too was absolutely frozen. Look at the edges of where the piston and
>the cylinder come together. There should be a snap ring which retains
>the piston (when it isn't frozen in place). Remove the snap ring. At the
>opposite end of the master cylinder, there should be an electrical
>pressure activated brakelight switch. Remove it. This will allow an
>opending through which you can pour "Liquid Wrench" , WD-40 or some
>type penetrating oil. I would fill it up with oil and allow it to sit
for a few
>days. After sitting a few days, pour out the excess oil. Using a long
>narrow punch, through the pressue switch opening try knocking the
>piston out. Best bet is to have two people to do this. One guy should
>hold it steady on top of an open vice. The jaws should be set just wide
>enough to allow the piston to pass through, but close enough to support
>the edge of the cylinder. Expect to have to hit the punch pretty darn
>hard. I used a 3# hammer on mine. If it does not seem to budge, you
>may have to apply some heat. I prefer not to do this as it can screw the
>cast up if you get it too hot. It will also cause the inner piston seal,
>is naturally rubber, to burn and stink along with the penetrating oil.
>The above is what I did on my GPW master cylinder, with the exception
>of the heat. When I finally got it all apart, it was badly rusted inside.
>bead blasted it and then I honed the daylights out of it. It cleaned up
>but still had some VERY MINOR pitting which was bascially dark spots
>that could be seen, but not felt. It put a new rebuild kit inot it and it
>works great to this day, two years after the fact. It did leak a small
>amount at first, but after a day or two and some operation, it quit.
>I would have posted this to the list, but something about my address here
>at work makes all my postings bounce. Feel free to post it to the list if
>you so desire.
>Jim Rice
>'43 GPW
>'52 M38
>'51 M100 Trailer
>>>> "U. N. Owen" <> 10/29/97 02:42pm >>>
>Hello list,
>Mr brother and I are working on our 41 WC-6 Command Car.
>I was blasting the bellhousing and pulled the brake
>master cylinder off. After looking at the master cylinder, I got
>side tracked and started to take it apart. After pulling the cover
>off, I saw that the inside was 1/4 full of rusty flakes. I blasted it
>out and suprisingly it came out very clean. Now I don't understand
>the operational concept of a master cylinder, I've never really
>looked at one up close until now. Hopefully you guys can help
>answer a few questions. Now, try to follow along.
>There is a "push rod" attached to the brake pedal that runs into the
>master cylinder. That's simple enough, but the question is this. Where
>this "push rod" enters the master cylinder, it enters a hole that is
>cone shaped. Is the "push rod" meant to push this cone shaped
>apparatus forward (ours doesn't move at all, is it supposed to?) which
>creates the pressure? If so, ours seems to be rusted in place, any
>suggestions on freeing it up? I hate to just start banging away!
>Next, inside the master cylinder fluid resevoir, at the bottom, there are
>two small holes. Obviously to allow fluid passage. It looks like only one

>of the holes is actually drilled completely through into the passage on
>the other side. The other hole seemst to stop about half way, therefore
>going nowhere. Is this hole actually clogged?
>Lastly, I've got 3 of these things and none of them are in working order.
>Where can I get one, if I can't get any of these working? What would be
>a average price I can expect?
>Thanks in advance,
>Corey Elliott
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