M939 Air tank help

[simp5782]

Does anyone know or have a diagram of air tanks primary secondary any additional locations thanks

Go into the TM section and download the p2p manual. It has them all. Download it to your desktop. Follow the instructions it has.

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[jcollings]

P2p manual?

 

[Ford Mechanic]

P2p manual?

It's in the TM section at the top of the main page. But it doesn't help you, if you don't have anything to download it to as in my case.

As far as locations of the air tanks, follow your lines back that lead from the drains on your passenger side. There are only 4 tanks.

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[jcollings]

So as to those drains 1 2 3 4 so #1 being primary #2 being secondary ?
The reason being ever since I change my air dryer the primary loses a little bit more after it sat for a while then the secondary and I just wanted to confirm if if the primary tank is back there by the air dryer.

Thanks

 

[Ford Mechanic]

So as to those drains 1 2 3 4 so #1 being primary #2 being secondary ?
The reason being ever since I change my air dryer the primary loses a little bit more after it sat for a while then the secondary and I just wanted to confirm if if the primary tank is back there by the air dryer.

Thanks

Honestly I don't know, how much is it losing and how fast? Cause we're "supposed" to be draining the tanks daily. If I don't I tend to have a valve stick during cold mornings not allowing the brakes to release.
I use a spray bottle with dish washing soap to find air leaks.

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[simp5782]

So as to those drains 1 2 3 4 so #1 being primary #2 being secondary ?
The reason being ever since I change my air dryer the primary loses a little bit more after it sat for a while then the secondary and I just wanted to confirm if if the primary tank is back there by the air dryer.

Thanks

The tank in front of the air dryer is the wet tank. It feeds both tanks and catchs most of the water. Secondary tank is the lower tank under the passengers tank. Primary tanks are the other two. Some air loss after sitting could be numerous things. Unless its not a massive air loss in like 3 to 5 mins of sitting do not go chasing a potential bag of worms.

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[jcollings]

Simp 5782 greatly appreciated thank you very much

 

[jcollings]

What would you consider acceptable pressure loss in relationship to time with truck not running?

 

[Ford Mechanic]

Mine will lose 60 psi overnight. How bad is yours?

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[jcollings]

about 35 to 40 pounds before changing the dryer after changing the dryer I lose more like 70 on the primary side only although I did find a leak that I tightened up, I have to test again.

 

[simp5782]

about 35 to 40 pounds before changing the dryer after changing the dryer I lose more like 70 on the primary side only although I did find a leak that I tightened up, I have to test again.

More than likely you have a cracked diaphragms on the spring side if yor primary drops more than 30psi in 10mins. If you secondary is bleeding off and u hear no leak in the cab then the Q2 is leaking on the check ball seal and its leaking out the intake.

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[Ford Mechanic]

More than likely you have a cracked diaphragms on the spring side if yor primary drops more than 30psi in 10mins. If you secondary is bleeding off and u hear no leak in the cab then the Q2 is leaking on the check ball seal and its leaking out the intake.

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Good info there!

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[jcollings]

Q2?

 

[jcollings]

Also air loss described was overnight not in that short of period

 

[simp5782]

Also air loss described was overnight not in that short of period

That is good tho. Also good to drain your tanks overnight and leave the valves open. Takes someone longer to steal it.

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[jcollings]

I usually do drain tanks every night except occasionally l don't to see how good of a air seal I have.

You also described Q2 what exactly does that refer to?

 

[MtnSnow]

The Q2 valve is mounted on the vertical plate just forward of the front axle.

 

[jcollings]

You're not referring to the service and emergency glad-hand connection?

 

[Ford Mechanic]

You're not referring to the service and emergency glad-hand connection?

No that square plate under the engine has a air valve behind it.

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[Ford Mechanic]

I need a good couple day class on air brake theory and operation myself.

40 psi overnight is nothing I'd worry about. That's normal for most air brake trucks.

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