air system pressurization from outside source

[eplurubus]

Any ideas how to pressurize the air system of an '01 Mack using an outside source of air? Do I remove the air tank bleed valve and pump air in through there?

Also, just today, I learned that trucks of old had starters turned by air pressure. Why is that system pretty much done away with today? It seems like a good way to save battery power, especially in the winter.

[Rev.Vassago]

Any ideas how to pressurize the air system of an '01 Mack using an outside source of air? Do I remove the air tank bleed valve and pump air in through there?

Yeah, get the proper size fitting to screw into where the bleed valve goes, and hook your hose onto it.

Also, just today, I learned that trucks of old had starters turned by air pressure. Why is that system pretty much done away with today? It seems like a good way to save battery power, especially in the winter.

They were also a great way to not have your truck start, especially in the winter. The air systems on trucks are notorious for having moisture in them, and in the winter, that moisture becomes ice. Can't start a truck if the line is frozen. And also, can't start the truck if you develop an air leak that drains the system.

[Bandit102]

Much better to remove the line from the air compressor and put your air in from there. Once full, just disconnect the air supply and your system won't empty itself as there's a check valve in that line.

[Kranky]

Find the "pop off" (relief) valve on the air dryer.

Remove said valve, put a "T" fitting in where the pop off valve was, put the pop off valve in one port of the "T", and put a 1/4 NPT X 1/4" air line fitting into the other port of the "T". Connect a length of 1/4" plastic air line to the fitting, run the air line to a convenient location on the outside of the truck and use a 1/4" air line X 1/8 NPT female fitting and screw a Schrader valve (it looks like a tire valve) into the 1/8 NPT fitting.

Make a suitable bracket to secure the Schrader valve, and use zip ties to secure the plastic air line out of harms way.

This way you don't have to get dirty climbing under the truck to air it up, and it's connected at the air dryer, so all tanks in the system will get air.

[Kranky]

Here is what the "pop off" valve (relief valve) looks like:

[Kranky]

Here's a photo of a truck I put together where I work, showing the external air fill, just below the top step.

In our case we put a "male" shop air hose connector and a shutoff valve on it, that way we hook an air hose on, open the valve and pressurize the system. Once pressurized, shut off the valve and disconnect the shop air hose.

You can substitute the aforementioned Schrader valve for the shop air connector and shutoff valve.



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[devildice]

O.K, I hate to be the "dumb" one but I got to know......why would you want or need to supply air from an external source?

[Jackrabbit379]

O.K, I hate to be the "dumb" one but I got to know......why would you want or need to supply air from an external source?

That's where you hook up an air hose to the tank. For airing up tires, etc...

[Kranky]

O.K, I hate to be the "dumb" one but I got to know......why would you want or need to supply air from an external source?

One reason would be if a truck has dead batteries and is also out of air, you can pressurize the air system to release the spring brakes and then pull start it.

The reason we have them on all our trucks is so that when we have a truck in the shop and we're working on the brakes or some other part of the air system, we can keep the system charged, or re charge the system without running the engine and smoking up the shop.

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[Kranky]

That's where you hook up an air hose to the tank. For airing up tires, etc...

Actually, if you want to use truck air for filling tires, you should put a connection on one of the "dry" tanks.

Air from a connection piped into the air dryer as I described could be contaminated with oil & moisture, both of which are bad for tires.

So:

To fill system, hook into air dryer.

To draw off air for other uses such as tires etc., hook into one of the "dry" tanks.

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[allan5oh]

Or just do what I do, use the red gladhand. I even run air tools off of it.

Most trucks come with a schrader valve somewhere. Most freightliners are by the air compressor, and Volvos have it attached to the external governor.

[eplurubus]

Remove said valve, put a "T" fitting in where the pop off valve was, put the pop off valve in one port of the "T", and put a 1/4 NPT X 1/4" air line fitting into the other port of the "T". Connect a length of 1/4" plastic air line to the fitting, run the air line to a convenient location on the outside of the truck and use a 1/4" air line X 1/8 NPT female fitting and screw a Schrader valve (it looks like a tire valve) into the 1/8 NPT fitting.

Great idea! Thank you!

One reason would be if a truck has dead batteries and is also out of air...

Which is my case. I don't want to start it, but I want to move it.

[eplurubus]

Or just do what I do, use the red gladhand.

Do you mean connect the red air line from truck #1 to the red air line on truck #2? Interesting. It didn't occur to me that air could be pumped in via that line; it makes sense, though. That might be the easiest, quickest solution for now.

[Jumbo]

Do you mean connect the red air line from truck #1 to the red air line on truck #2? Interesting. It didn't occur to me that air could be pumped in via that line; it makes sense, though. That might be the easiest, quickest solution for now.

What he means is if you want to air up your tires or run an air tool hook the hose to the red glad hand.

[allan5oh]

Do you mean connect the red air line from truck #1 to the red air line on truck #2? Interesting. It didn't occur to me that air could be pumped in via that line; it makes sense, though. That might be the easiest, quickest solution for now.

I was talking more about using that air supply for something else, such as filling up tires or using air tools. It's possible that the red gladhand can be used for air in, but that may damage the tractor protection valve, I am not sure.

[Kranky]

You can't pressurize the air system thru the red gladhand.

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