1943 Dodge WC51 Master Cylinder Repair and 2025 Tractor Show

Ah yes, brakes. One of those systems on an old vehicle that usually needs a lot of work. And this truck's brake system falls into that "usually" category. I figured I'd try the easy three-step fix first. You know, the Dead Dodge Garage (youtube) method.

Step 1 - see if brake pedal goes to the floor

Step 2 - fill the master cylinder with brake fluid

Step 3 - pump the brake pedal until something changes - hopefully the pedal starts to get firm

With this plan in mind, I'll dive right in. The first order of business is to get access to the master cylinder (MC). On virtually all modern vehicles, it's under the hood and in easy reach to allow for servicing. This truck? Nope. It's under an access panel in the cab floor. Fortunately the panel was held in with just "a few" bolts. Eight to be precise...

Once I got the panel off, I searched for the MC. It was nowhere to be found, but in my defense I was looking for a normal-looking MC with a large lid or cap on top. After much searching, both in the cab, under the hood, and on the floor, I found what must be the MC. That brown rusty cover kind of in the center of the photo below with six bolts holding the cover on, and a very small 1/2-inch pipe plug covering the fill port.

Below is a slightly better shot of it.

I tried loosening the pipe plug cap with a 12-inch adjustable wrench but the cap wouldn't budge, so I tried a little heat, which did the trick.

Looks pretty empty in there. I used a long transmission funnel and filled the thing with brake fluid, then did the Dead Dodge Garage pump-until-something-happens trick. It actually did work to some degree. I got a fairly firm brake pedal. Problem was, if I let it sit for just a couple minutes, the "prime" was gone and I'd have to pump eight or ten times to get brakes again. No matter, it should work well enough for my goal of getting the truck on the road this afternoon, which happens to be Veterans Day 2024. It just seems appropriate.

And here she is, back on the road on 11/11/2024 (Veterans Day appropriately enough). It's been at least 12 years since it's seen the light of day out on the open road.

Sigh. It's two days later and I noticed something seeping out from under the truck. Brake fluid, I presume? Yep, brake fluid. Time to remove the MC and either do a rebuild on it or buy a new one if this one is too pitted to use.

That was not an easy process to get the MC out. Even though this is a truck, and an old, simple one at that, everything I seem to touch to fix is difficult to reach. Yes, that includes the MC. After about half an hour, it is out and on the bench. Notice in the photo below the "DPCD" cast in the MC to the left of the number. That means this is an original Dodge/Plymouth/Chrysler/DeSoto part. I don't know if it's original to the truck but it is genuine Dodge.

Here's a little better look at that DPCD.

This is the strangest top cover for a MC I've ever seen. I suppose it's designed for "combat" duty.

This doesn't look so good.

Nope, not good at all. Notice the small DPCD cast into the underside of the lid. It's really too bad this MC's bore is pitted so badly. It would have been nice to reuse this vintage piece.

After quite a bit of honing, the bore is still severely pitted, so this MC is not usable in its current condition. Time to order a new one. They're "only" $130 (plus shipping and tax, so let's say $150), which isn't really outside the realm of sanity considering how old this truck is.

Ok, it's several days later and I have decided to try and sleeve this MC myself. I have the equipment in the basement, so why not give it a try, right? Yeah, things can go south real easily when boring out an original Dodge MC. I'm willing to take the risk though. We shall see in several days if I made the wrong choice. I can always still just buy a new MC but I've already ordered a kit to put new guts into this one when or if it gets fixed.

I did buy a new tool to do this job. It's an adjustable boring head. It was $66 from Amazon. I bought the one that has an R8 shank, as my mill is that size. The mill unfortunately doesn't have the range needed to bore a 6 inch long bore, so I'll be using the lathe. It requires a bit more fixturing to hold the master cylinder rigidly in place. The photo below shows the 90 degree plate I'll bore a hole through to hold the MC.

First a 1/2 inch hole, then a 1 inch hole, then the new boring bar gets to play.

I chucked the body of the boring head into the chuck. A previous photo showed the shank of the boring head was held in the chuck but I noticed it flexed some. This is a lot more rigid.

A 2 inch hole is completed.

The MC is now mounted on the plate. I threaded three holes so I could use the MC bolts to hold the thing to the plate.

The bore of the MC is 1-1/4 inches and I was able to find a 10 inch long section of the same size bar stock in my small steel stash. I stuck the bar stock in the bore and indicated along the part sticking out so I could get the MC positioned exactly parallel to the lathe axis.

I do need to still buy a 7 inch long boring bar, as the long one that came with the boring head is a couple inches too short. I made a small test cut with a short boring bar and it looks like things will work quite well. Cast iron is fairly easy to machine.

The long boring bar came in, so we're off to the races with this part of the job.

The boring is complete and there is some chatter but it isn't going to be a sealing surface so it will be fine.

 The new bore measures 1.356" so I need to find some 1-1/2" bar stock.

Fortunately I happened to have a chunk.

Below is the outer diameter turned down to about 1.355" so it will be a tight slip fit into the MC bore. I'm using a cutoff tool to cut the bar to length.

Next is to drill and bore out the center of the bar.

I had to bore from both ends, as there was too much flex in the boring bar to do an adequate job from just one end of the sleeve. There was a slight mismatch in the center of the sleeve due to boring from each end, so I used a brake cylinder hone to smooth the transition. I think it will be fine....

Here's a test fit of the old plunger in the sleeve. It fits nicely.

Here's a test fit. The sleeve doesn't slide all the way in but it should press in easily.

It's a 7 month gap between the above and below photos, as I got a couple "new" tractors in the collection that I "needed to" tinker with. I know, I have too many projects. Anyway, the below photo shows some JB Weld applied to the outside of the new sleeve.

I used a Harbor Freight hydraulic press to get the sleeve pressed into the MC.

So far so good.

Looking down into the reservoir, there are two small holes in the casting that I need to drill through the new sleeve so brake fluid can get into the master cylinder bore.

A new cover gasket is made.

I decided the MC needed some paint protection.

Here's the new kit.

And it's all back together.

I got everything reinstalled and the brakes bled, then took the beast out for really its maiden voyage since I bought it. Previously I had driven it on the road outside the house for a few hundred feet but for the maiden voyage I took it around the block and got it into fourth gear. The brakes worked but something is definitely out of adjustment, as I had to stand on the brake pedal to get the thing to stop..... eventually.

The main reason for the push to get the brakes done was to drive the truck seven miles to the tractor show my club was putting on over the weekend. I got the brakes done on May 2nd and the show was May 7 and 8.

The truck did make the trip both to and from the show without incident, although the brakes made the drive the most harrowing experience I think I've had in a vehicle. My wife drove behind me both ways, as the beast has no turn signals or brake lights. I did use hand signals so I had that going for me...

This photo below shows the WC51 at the show, it's on the far right.

This next photo shows the small 300 watt Blue Diamond generator (link here) I brought to the show, the little grey thing in the lower right foreground with a trio of 65 watt light bulbs it's powering. That thing ran without a hitch for two days straight.

This next photo shows another row of tractors at the show. Three of them are mine, which are a John Deere LA (second from right), JD BO (third from right), and the JD BN (fourth from left, difficult to see). The last afternoon of the show, I enlisted the use of the BN to pull the kiddie train around, as the Allis Chalmers RC on duty lost oil pressure and started making a racket (coincidentally the one time I drove it).

Here's a better photo of the BN at the show that someone else took. The fellow who took this photo owns the Farmall 300 next to the BN. His tractor is nice. He paid $2000 for it.

Update 6/14/2025: I was under the truck today and noticed this:

Yes, that's brake fluid. It's coming from the left rear brake cylinder. I really didn't want to have to mess with the brake cylinders at this point in time, but I can't really drive the truck with this issue.

Here's a little side tangent. I thought I'd put together a sketch of how the brake adjustments work on this truck. It is a bit different than normal drum brakes.  The brake shoes are the black/red things, the brake drum is blue, the wheel cylinder is orange, and the adjusters are the yellow and green dots. The yellow dots are actually eccentrics that move the shoes up/down and in/out. The green dots move the shoes in/out only.

The left sketch below shows properly adjusted shoes that are centered inside the drum, and when the brake cylinder pushes the tops of the shoes out, all of the friction material contacts the drum. The right sketch shows the shoes up too high, and when the brake cylinder pushes the tops of the shoes out, only the tops of the friction material contacts the drum. My brakes were all adjusted too high when I bought the truck, and the brakes were practically useless. I've since adjusted them to work better.