Remote booster bypass
 

I'm not sure of the protocol, but I have a brake question about my '47 2 ton. Once again I know this is the wrong forum, but with hundreds watching at a time, compared to ten or twenty, I thought I'd get a quicker or more opinions here before I get off work today. So here goes.... Because my remote brake booster was shot, I removed it when I did my brakes. I just don't want to spend another 300.00 at this time, as it won't get hard use for a while. The master Cylinder has a five sided brass block on it's tail with five brake fittings plumbed into it. I kept the right front to it's original place, same with left front and rears. I could have plugged the other two ports, but read somewhere where someone said to run a line between those two ports, basically a loop in the circuit that had previously run to the booster. On my first real test drive yesterday, the brake pressure continued to build until I had to crawl under the truck and relieve the pressure by bleeding off a front wheel, just to keep it rolling. (All 4 drums too hot to touch :-hair). Then good to go if I didn't brake. I have a good 1/2" play in the adjustable push rod, even when they were bound up. Only thing I can figure is I bypassed it wrong.... Or is it something else? Anybody done this? I will buy some plugs at napa today when I'm in town, jic.

I think this is what you are looking for:

http://bigdigiman.com/fp/ford-trucks...kemanifold.jpg

As you can see, simply connect the lines that ran to and from the booster together.

That's what I did, connect those two together. I will check to make sure I got all the other lines back in the right holes. Thanks for the diagram, it is exactly the shape of the block I have. Any reason not to plug the holes to and from the booster? Edit: now I see there would be nothing to feed the system with the stop light/feed circuit blocked. What else could build this pressure?

You do NOT want to plug the holes to and from the booster. If you look closely at the diagram, the system would work like this in that case:

You press the brake pedal which pressurizes the brake fluid in the master cylinder. When the master cylinder is pressurized, that pressure transfers through the banjo bolt in the back of the master cylinder into the brake system manifold pictured and the brake stop switch. At this point, the brake fluid pressure goes out the "to booster" line. If you block this off, your brake pedal will be hard, but no pressure will be transferred to the wheel cylinders. This is not good - so again, you do NOT want to plug the holes to and from the booster.

It may be easier for you to conceptualize the brake manifold as two seperate brass fittings (And since the original piece is not reproduced and hard to find, many people actually end up replacing it with two fittings like so).

The first fitting is a standard T brass connector consisting of these three lines:

1) Direct line from the Master Cylinder (Banjo Bolt)
2) Line to the Stop Switch (Banjo Bolt Head)
3) Line to the second fitting (To booster)


The Second Fitting has 4 connections:

1) An input from the previous fitting (From Booster)
2) Front Left
3) Front Right
4) Rear Axle T fitting

At first I didn't get it, but then I looked closer and edited my post. I still haven't looked at my setup since you posted the manifold diagram. Maybe after I finish my ice cream I will run down to the shop and have a look. There were a lot of bends in the line and tight tolerances, so it would have been hard to switch them up, but not impossible. I'm so glad to have a diagram, because without x-ray vision its hard to see where the fluid travels in there.

So, I went down and sure enough, I have two of them reversed. But now that I look at the diagram again, I wonder if the reversal is the problem. I have the one on the left that went to the booster near diaphram looped up into the top one which is labled 'to rear wheels'. The rear wheels are fed by the one in between those two, which is labled 'to booster end fitting'. But... since these two are fed by a 'Y' in the internal circuit, isn't that about the same? I thought I'd found a simple solution to my brakes binding up and locking while underway, but I think the plumbing is ok, unless I am missing something. What I guess I'm saying is as long as I'm feeding the manifold with a line from the central stop switch circuit (master cyl) into the central system, it shouldn't matter what else is in the factory position, as the lf, rf and rears will all get the same volume and pressure. If you agree that it's ok how I have it (a pita to change back), I will try shortening the pushrod a bit more, and see if I can drive a few miles without all 4 brakes binding harder and harder until I have to downshift to 3rd on the flat just to keep going. Slightly cracking a bleeder releases them and she rolls as free as can be..

You are correct that you can pipe the outputs any way you'd like as long as you feed the internal Y of the manifold. Sounds like your plumbing is fine. If things lock up and you have to bleed them to get them going again, I would suggest rebuilding your master cylinder. NAPA has rebuild kits available. I've rebuilt the cylinder with out removing it from the vehicle. Saved lots of hastle dealing with the plumbing. Just be prepaird for the brake fluid rain.

Here is a link to the NAPA part:
NAPA AUTO PARTS

Edit: The more I think about it, it seems that it could be the valve in the master cylinder failed or is installed backwards - I did that on my first master cylinder rebuild and I think my symptoms were very similar to yours.

All I did was hone it and put in a kit I got at napa. It seems tight and no leaks. The PO could have installed the valve backwards I guess. I will shorten pushrod just a tad bit and try again. Thanks for all your help.

So, I've been preoccupied with work stuff and for some reason buying a '58 f6 fire truck. Now I'm back at it with the locking brakes on my '47. All 4 drums are adjusted properly just shy of dragging. All 4 wheel cylinders and master rebuilt last winter. Push rod is as short as it can be adjusted. There is about an inch of pedal travel before any resistance. I can drive the truck about a mile before I feel the resistance of the dragging brakes. This mile would involve quite a bit of braking. The more I brake, the more resistance I feel. At this point I can be headed down a fairly steep hill and the truck wont roll. After the initial application of the brakes, the pedal is rock hard. Now, I go under a front wheel and bleed a front wheel cylinder and it rolls perfectly. I have read much about brake hoses collapsing inside, holding the pressure, but I doubt it's all 3 hoses. I drove into my shop with the brakes hot and stuck on, and jacked it up on all 4 corners. I could not budge a single wheel. Another interesting thing is the brake light remains on until I release the pressure at a bleeder. Instantly the wheels roll without a sound and turn freely. I am beginning to believe that when I rebuilt the Master cylinder, I installed the valve backwards. Can someone describe how this valve works and what it does? If it was facing the other way, wouldn't it be impossible to force fluid through the system? Also, anyone have a diagram of what's in the MC? Looks like if that's the case, I could fix it from underneath. Had been hoping to do the parade with a load of salvaged beams on the bed, but now not too sure. Thanks so much and sorry for the extremely long winded post.

Here is the diagram
2178 is the valve

harleymsn beat me to the Master Cylinder breakdown picture...
http://bigdigiman.com/fp/ford-trucks...terrebuild.jpg

Since it's a big truck, you can simply get on your back and correct the valve from under the truck with out removing the master cylinder or playing with the brake plumbing. It should go something like this (forgive my memory):

*Remove the cotter pin thelarger pin it retains connecting the brake pedal to the push rod.
*Remove the pushrod
*Remove the rubber boot
*Remove the retaining snap ring CAREFULLY... When that snap ring comes off, the master cylinder will releive itself of all the brake fluid it contains and the inner components will fly out as they are sprung loaded. It would help to use a turkey baster or somehow remove much of the brake fluid from the master cylinder beforehand.
*If possible, observe the valves orientation as it is removed from the master cylinder and compare to the breakdown diagram. For your sake, I hope it is backwards.
*If all the components look good, reinstall per the diagram. If you need new parts, NAPA has a rebuild kit, napa part number UP 1.
*Reinstall the rubber boot, pushrod, and brake pedeal linkage.
*Fill Master Cylinder with brake fluid and bleed your brake system well.
*Last, but not least, take a test drive and confirm you are ready for that parade!

Thanks, Ill do it after work tonight, that is if my employees don't work me too hard. I have been on their case about pushing to the finish line on a couple of jobs with July 4th deadline. The summerfolk are returning from their winter dens, but they bring fresh $ from the mainland! I appreciate all the help. Thanks!

OK, here's what was in there. Starting with the bottom or blind side of the cylinder to the right in the photo.... Rubber washer/grommet seal thing, Valve which is pretty sure the correct way, spring attached, Main cup, Piston with new rubber installed from kit, Thick washer, spring retainer, boot. A mechanic friend I questioned suggested that the supplied piston may be too long, preventing the resevoir from refilling or the excess bleeding back in. Measuring the feed hole in the MC, I find that at rest with the piston against the retainer/washer, the small feed hole is located between the two cups. Is this the right place? Is the rubber gasket/seal supposed to be the first component to the right? Edit: Looking at the photo, I have set the main cup with the brass ring facing opposite direction of how it was installed. The flat, brass ringed face goes against the flat, perforated face of the piston, as in the factory drawing.

I question the fourth item from the left, primary cup. Was it installed as shown, leaning against the piston? I believe there should be a seal at the left of the piston. Makes me want to go out and disassemble a MC I removed, just to see how it is assembled.

Yep, looks backwards