The Stovebolt Site Forums The Parking Lot Big Bolts Air Brakes II

I see post on air brakes. I have a small IH, with them, half of system was off truck in cab when I got it. It also had dual controls, which I removed now. The air tredal (pedal) was just a plug or two in a junction block to remove one side. I have two tanks, in series. ON last tank was a hose, then water trap (plastic) and more hose. I have the system all up and running, but not sure on water trap. I'm thinking it might be for some added feature that was on back at one time. This was a sweeper truck, and had air controls I took out of cab for the brushes, which were all gone, and an engine was on back one time to run all this. I can get pressure and brakes with system as is if I close off that last hose off trap. I plumbed it into a tee where rear brake hoses run off, but that only pushes all the brakes on when pressure gets up. SO, I wanna know if this thing is even neccesary or part of orig system or if it may have gone to a third tank for diff function? My current tanks have bleeders for water, manual. I have hose from pump to first tank, hose between tanks and one big metal tube off last tank that goes up front to system. It goes thru system and back to rear at tee for brake hoses, and same for front wheels. These brakes do not appear to have the modern spring pressure to keep on when parked, or no pressure. I pulled truck home as it was setting. I have an auto trans and cable parking brake on back of it. There is no trailer controls or added system. This seems like much simpler system than I can find a drawing for in most brake mans and parts books I have now. Modern trucks have "back-ups", trailer locks, emergency, and parking features that mine does not have. I'm thinking of just removing the hoses and water filter off the last tank and plugging line at tank. I was told if no air flows thru the filter, no action takes place. With plug at end of hoses as now, no flow takes place. AND, being plastic, if it got hit with stone or such accident, I would loose pressure and brakes while driving, another hazard maybe.
So, what you guys think, take it off? Was it for something else?
I only have a parts book, no shop manual for this IH. This is a B1710 Cargo Star tilt cab, short wheelbase, 345 gas, Allison trans, power steering. I think it will make a nice driving truck once I get brakes fixed correctly. As noted, I have brakes now, haven't taken out to test yet. Think I need more pressure from my slow pump. I put on new governor, but seems slow to get pressure up, and drops quite a bit in use, in garage testing. I need to get the pump belt much tighter first thing, it is pretty floppy. I'm hoping that is all.

Modern air brakes are pretty simple if you realize that there are really two separate systems involved. The emergency (or park) system's job is to keep the springs in the brake pods compressed while the truck is in motion. If your truck does not have dual chamber (spring) brakes you only need to concern yourself with the service brake circuit (with a few changes). The treadle valve (brake pedal) sends air to a relay valve. This relay valve opens and allows air stored in an air tank to flow to the service brakes which applies them. When the brakes are released the relay valve closes, shutting off the flow of air to the brake pods from the tank WHILE dumping the air pressure in the lines from the relay valve to the brake pods. It sounds to me like a relay valve is missing or stuck open.

On the older trucks, when the brake valve is released, air pressure from the tanks goes to the brakes to hold the vehicle from moving but when the air leaks off, the brakes release and the truck rolls away. That is why you have a manual parking brake on this truck. When hooking up to an older trailer without spring brakes, you had to first connect the air lines and charge the brake system before attemping to hook up or else the trailer would roll away from you unless the wheels were securely chocked.

Hope this helps. I think if you study your current brake schematics and isolate the service brake components, you will be able to figure out what items are needed.

I'm having a hard time picturing the plastic "trap" you describe. It sounds more to me that it may be an oiler that was installed in line with an air/electric valve to operate an air ram or other device on the old sweeper bed. I've seen the air rams on belly dumps set up similar to that. Most air driers I've seen on trucks are of steel construction and are plumbed between the compressor and the tanks.

Joe, this thing looks just like something you would have on your air compressor in garage. In and Out hose, plastic jar, with little rubber valve on bottom. You push valve to side and the air or water maybe blows out. You and otheres think it might be for something else and not needed on brakes of truck. Guess I'll just remove it.

Racecarl: If the brakes are working now and give that "whoosh!" sound when I lift foot off brake each time, wouldn't that mean the Relay valve is working? I can push and hold brakes, don't seem to go down in pressure that I can tell.
I'm wondering what "regulates" the pressure of application from treadle? My owner's manual says on downhills to apply brake on and off, not to partially hold like vac brakes, as the pressure will bleed off too soon. Is there any "feel" in the pedal on air brakes? Man, gotta get this rig out of garage and try to run it! Need to finish some little things first though. I got the park brake working now, feel less risky for test drive!

That isnt that terrible of an old truck, the jar your talking about sounds like a water dump valve of somekind maybe??? is the rubber thing like a check valve like a one way valve on a boat drain? if its pressurized? or could it be a place to add alcohol to the sytem maybe.??? Dunno just try it without it... You cant feel air brakes the way you do with hydraulic, First off air compresses...and also the pressure your applyin from the pedal isnt direct to anything that you would feel like hydraulics are to cylinders.....and as far as manuals and instructions they will tell ya anything that isnt necassarily true... Any manual will tell ya not to ride the brakes downhill for any length of time..... But due to the fact you cant feel air brakes the same way...they would probably tell you that cuz..you couldnt feel if they were getting hot and fading like you could with hydraulic... dunno....
Ohhhhhhh i see after rereadin ur last post...yeah that little jar is just a water trap...the push thing is the drain for it...(its a schradervalve type thing in the rubber) you can see water in it to drain.. its not hurting anything where its at...or it wont hurt to remove it...and if i remember right...the second tank is just a reserve air tank,,, it has a check valve in it if the first tank is drained,,,it could also be the trailer supply tank, as the other guy said to charge the trailer brakes. most systems have two tanks anyway with one as a reserve....or emergency tank, as in you stated if ya loose air you still have a second tank to try to get stopped.....those air brake systems can get pretty complicated. Also one last thing,,, the slow buidup..??? uhhhhhh it takes abit to build air..and yeah it dont last long without it running to pump air... belt driven compressors arent any worse than gear driven ones. Id say if i remember right, from no air to a full 120lbs would take about 3 minutes or so at least at high idle.... there are specs for it... Same with bleed down... You hold down the pedal and shouldnt drop so low , in so many minutes but i cant remember how long?

little fmcsa handbooks give the specs for bleed down time etc, you can pick them up at most truckstops. Jar may be for collection of moisture not shore haven't run across it. seems like trucks of the 70's had a place to introduce alchol into air system but I don't remmember now how it went. nowadays with airdryers and proper and regler bleed off not much of a problem. Sometimes pour airline antifreeze in trailer gladhands if there's a problem. suggest you install pull type bleeders on air tanks so you can drain moisture from tanks regularly pain in butt laying underneath truck in freezing weather with a flare trying to thaw frozen valves