I only have 2 air tanks. they are the same size. tank# 1 on drivers side & tank #2 on gauge is located on pass side. the # 1 tank supplies the real wheel brakes. can see the lines out in the open, no mistake there. at one time when applying brakes both tanks would drop simutaneously. A two way check valve connects both the Primary and Secondary tank and this gives you Blended Air. I wonder if this could cause prob if defective?

 

In a dual air system, there has to be three tanks. The supply tank (also know as the wet tank) Secondary (usually feeds front service) and Primary (usually feeds rear service brakes). The supply (wet tank) has two lines from it, one to the Primary and one to the Secondary. Both the Primary and Secondary tank have one way check valves that lead back to the Supply to prevent the tanks from draining, if there is a break in the line from the Supply to the P or S tanks. In other words, the air can only go FROM the supply TO the P and S tanks.

What you might be seeing is that the Wet and Secondary are just one physical tank, but has a partition in it that would then create two reservoirs. This is what I have in my International. Look at the tanks and see how many drain co*cks you have. If you have one tank that has two drain co*cks, one on each end, then that is probably a split tank. The other tank should be the Primary and it more than likely has only one drain co*ck.

Let me know what you see. We can go from there.

If the two way check valve is defective, then when you drain one tank with a drain co*ck, both should empty.

Also, I am not sure if the system is defective, maybe just not operating like it was when new.

 

there are only 2 air tanks under my truck. i'm sure.

 

Two Tanks, but should be three reservoirs. You should have three drain ****s. As I said, Wet, Secondary and Primary.

Maybe the Wet tank is hidden, I have seen that. And, I have also seen tanks with out drain co*cks.

Find the dryer, and chase the line back to the tank it is connected to. That should be the Wet Tank.

Also, the wet tank probably has a Safety Valve on it.

My International has two physical tanks, with one having one drain co*ck on one end (Primary) and the other having two drain co*cks (one for the secondary and one for the wet).

I have never seen a dual air system with only two reservoirs. I have seen them with more, that is very specialized equipment, like fire trucks.

And Dual Air has been out (and mandatory in almost all cases) since the mid 1970's.

 

Mine is a intl. also. it has 2 physical tanks. tank 2, on pass side does have a pop off valve in it, cause I replaced it a while back when I found it leaking. will trace from dryer to wet tank.

 

If it has a pressure relief valve, then it has to be the Wet.

That is because you have to protect the system from over pressurizing in case the governor fails, and you want that to be early in the system.

This doesn't make any sense..... UNLESS someone made modifications with the air system that did not know what they were doing.

There are Drain co*cks on all all tanks

There are pressure gauges ONLY on the Primary and Secondary tanks

Safety relief valve is on the Wet tank, or earlier, could be the dryer

Secondary and Primary tanks have one way check valves at the access point from the Wet tank

A two way check valve is between the Primary tank and the secondary tank.

If you have something other than this, then I am at a loss to explain it.

 

both air lines from dryer go to the one tank on pass side. real aggravating thing is I soaped entire truck. every line front, back, bottom , top, every fitting everywhere. cannot find any leak but entire sys will leak down in 4 hours from 120 psi. A leak that big should be noticable. it's not. if i found the leak that causes all the air to leak out, i'm sure it would help my loss of air when braking. they sell a leak detector that glows in the dark. in warmer weather, i thought about putting 10-12 oz in each air tank & waitng for it to work thru the sys & show itself. or take it in somewhere. wich i would of already taken it in if i knew someone could find the leak. no one can tell me they have the equip to find for sure the leak. cost is not a prob, it's the cost & still having the leak. any way thanks for all the help.

 

Maybe its something thats hidden, like the valve for the airhorns, occasionaly a leak into the trans, slave valave on the side ot the trans, or a range shift cyl leak. Try plugging the line to the trans while the trucks parked........... & the leak sounds like a seperate problem.

What if the foot valve was changed at one time & the lines got mixed up so the secondary air supply is now feeding the primary brake circuit?

If you look close along the airtank you should notice a seam or weld part way along, its 2 tanks built into one with a check valve between.