The Stovebolt Site Forums The Parking Lot Big Bolts '72 C60 air brakes explained???

I have a 72 C60 dump truck that I use on the farm. After this cold winter it has seemed to develop several leaks around components that I have no idea what their function is. None of the lines are leaking. I assume there was condensate that froze and botched things up.
One leak is coming from what looks like an allen head plug in a gadget located on a frame crossmember just above the driveshaft. Another leak is coming from a round cylinder about 1 1/2" diameter positioned vertically on the rear of the air compressor. There may be others but these are the obvious ones.

The air brakes on this truck are the type that are not locked when air pressure is lost. I'm not sure what this type of system is called and have searched unsuccessfully to figure out the workings of the system.
Can anyone here explain how this old system works. Are the parts still available?
Thanks, Dan

The thing on the compressor is your governor. They fail quite regularly and I always keep a dozen of them on hand.

http://www.ryderfleetproducts.com/haldex-midland-kn18530/d2-air-governor-no-core-p-u55-kn18530

Your description is rather vague, but it sounds like your quick release valve. I keep a dozen of them on hand too.

http://www.ryderfleetproducts.com/haldex-midland-kn32005/valve-quick-release-3-8"-ports-p-u55-kn32005

Spring brakes were not required by law until Sept of 1975, but most larger trucks had them as far back as the 50's when they were invented by MGM. Although the parts may not look exactly like what you have, all components of an air brake system are still available

The governor cuts the compressor out at about 120 psi. When you step on the brakes, the foot valve http://www.ryderfleetproducts.com/haldex-midland-kn22150/valve-foot-p-u55-kn22150
sends air to the steering axle brakes and the relay valve for the drive axle. They look something like this. http://www.ryderfleetproducts.com/haldex-midland-kn28085x/valve-relay-plus-core-p-u55-kn28085x You should have a quick release in front and back to release air quickly when you let off the brakes. If you have room for spring brakes, I would highly recommend adding them. Nothing else will really old a truck except chock blocks.

A valve like this is used to operate the spring brakes.

http://www.ryderfleetproducts.com/haldex-midland-kn20021/valve-dash-pp1-hand-operated-p-u55-kn20021

It will pop out at about 60 PSI and set the brakes or of course you can operate it manually as a parking brake. I would forget about the old copper tubing they used and use nylon tubing.

http://www.ryderfleetproducts.com/velvac-20136/nylon-tubing-3-8"-p-u80-020136

If you are near something like a Fleetpride, they can fix you up with everything.

Thanks! I have a better understanding of them now. The relay valve was what had me puzzled as to its function. It seems mine is leaking at what appears to be a allen hex head plug which is baffling. Maybe it is not a plug and is open at the bottom.
It's all hard to tell until I get it cleaned up.

I did replace some of the copper with nylon a couple of years ago.

It doesn't get much use these days as the old 366 is pretty tired and worn out. I try to start and move it around every so often to keep the rats confused. Yesterday I noticed the air leaking.
Time to address the brakes.

It does have an exhaust at the bottom, and when they fail, they usually leak out of the exhaust.

What typically fails in the relay valve? And, can they be rebuilt?

They start leaking out the exhaust. I would not attempt to rebuild the one you have yourself. If no one has monkeyed with it, it should have a tag. If there is no tag, I can probably identify it if you will post a picture. Or take a look at this Bendix catalog.

http://www.bepco.biz/Catalogs/AirBrakeCat/80-82.pdf

The R12 valve is a popular valve that is still used today.

If you look at the R8 valve, it shows a picture of of the bottom side. The round piece of rubber in the middle with what looks like a screw in the middle is the exhaust.

I'll be at the ranch today and will look for a tag.

None of the Bendix valves looked familiar. I'll see if I can get a picture of it today.

Thanks.

Finger pointed to where the leak is.

[IMG]http://i61.tinypic.com/33e25gy.jpg[/IMG]

There is also a lever in the cab labeled "truck tractor protection" Two positions "Normal" and "emergency". It leaks in the normal position, brakes always worked fine in the emergency position. I don't understand the purpose of this lever either.

If you haven't already found it Bendix has an air brake handbook with lots of diagrams, pictures of components, and explanation of how things work.
http://www.suspensionspecialists.com/techinfo/Bendix_Brake_Handbook_2009.pdf

It doesn't look like a Bendix. It could be a Sloan. Where do the lines go. It may be an old tractor protection valve. If it has a tractor protection switch on the dash, it was once tractor equipped. The normal is for driving. Emergency kills the air supply to the trailer. If it is now a bobtail, you don't need any of this. What leaks when you have it in the normal switch. Is it the valve on the dash, or is it the valve in the picture? If it is the valve in the picture, you don't need any of this if you don't pull a trailer and it is best to plug it at wherever it gets its air.

Thanks for the link Grigg! The operation of the lever in the cab makes sense now. I assume this truck was a tractor before someone installed the dump bed. I've never seen any trailer lines.

I still haven't found what type of relay valve it has. Nothing looks like the one I have.

I really should do a compression/leak down test on the 366 engine. If it looks like bad news I may just scrap her out.

If I recall it leaked at the lever in the cab. Perhaps they removed the trailer lines there. i don't know.

I did notice on one end of the valve pictured it was stamped "Tractor emergency". There are two other connections on top that have pipe plugs installed.
I haven't had a chance to trace the three lines out.

After looking at the image closer, the 2 mounting bolts at an angle are a dead give away. It is a spool valve used for a tractor protection valve. If you don't have a trailer, you don't need it anyway, but they are still available. http://www.peterbiltparts.com/brake...706bxw/?gclid=CJCzmsON7rwCFS1p7AodagsA_Q

If it runs, I wouldn't worry about compression readings. Anything with air brakes is handy to have because air brakes are so much simpler to maintain than hydraulic. And you have to remember that even if you have air leaks, you have a compressor to replenish the air. When hydraulic fluid is gone, its gone and you have no brakes.

And, it has an air horn!

Thanks, I'll look into removing the leaking valve.
She runs but is pretty slow coming up the hill. Oil pressure is good so I wondered about pulling the heads and just throw some rings at it and lap the valves. It's got really good tires.
Like I said, we just use it around the ranch. Mainly digging out dry ponds and moving the silt to cover up caliche to get a little grass to grow.
As long as brake parts are still available I'll keep her going.