Towing XC Chassis

[Troubleshooter]

According to my Freightliner XC Chassis manual, it states that when towing the vehicle, auxiliary air must be supplied to the Schrader Valve (looks like a tire valve) on the Air Dryer, in order to air up the suspension, and to release the spring brakes.
Others that I have talked to with the XC Chassis have stated that they supply auxiliary air to the auxiliary air manifold located in the front of the chassis,for this purpose. I have been told that this cannot be done, as there is a check valve in the air system that will prevent adding air from this manifold.
Today, I decided to see if there is a check valve on our XC chassis.
I made up a male to male automotive quick disconnect fitting, and connected my shop compressor to the front manifold, after dumping all the air from the on-board tanks.
Immediately after connecting the aux air to the front manifold, I heard a "snap", which evidently was the check valve closing, as I was unable to air up the system using that manifold.
Now, at least, I know that if I need to release the spring brakes, or air up the suspension for towing, I have to use the Schrader Valve.
While I carry a 50 foot 3/8" air hose, for airing up my tires, I also make sure I carry a locking chuck in the event I ever need a chassis tow.

Bill
2002 Discovery
2002 XC Chassis

[J Walker]

Troubleshooter, It is good to know where to air up the system. My 200 XCS is probably the same, but I don't know why the check valve is in there. There is information about the front air access being for the purpose of airing up the system for towing, and I believed it. My air tanks stay pressured for weeks at a time so I would be good for towing once they are pressured. I don't have air bags so that might make a difference.

[Troubleshooter]

Jim,
Like you, I don't know why they would put a check valve between the air manifold, and the tanks, unless they didn't want unfiltered air being introduced into the system. By applying air through the Air Dryer, it would be filtered prior to being introduced to the system.
And, like your unit, I don't have any leaks in my air system, as I have left it sit for several months, and still have over 70psi in the tanks when I fire up the rig.

From the XC Chassis Operators Manual, Chapter 10, Under "Towing"
"

Before attempting to tow a vehicle with air suspension
(and during the towing operation), ensure
that the air suspension is properly aired. Air
the suspension through the Schrader valve on
the air dryer. Attempting to tow a vehicle with an
improperly aired suspension may result in damage

to the chassis and body."

From the Freightliner document "Knowing Your Chassis"

AUXILIARY AIR SUPPLY

"Manifold provided for
auxiliary air source
– Up to 120 psi
• Can be used for:
– Air horn supply
– Fill tires
– etc.
• The only approved

location for tying into
the air system."

Based on these two documents from Freightliner, I can only assume they don't want the system aired from the Auxiliary Air Manifold.
Please note: I can only speak for MY XC chassis. Yours may be different.


Bill
2002 Discovery XC Chassis

[J Walker]

That inspires me to look at my manuals again. I read the thick stack of material that came with my MH for about two days and then extracted the service schedule which I keep on my computer. The documentation is not that user friendly since it covers several options. I expect that my air system works like yours but I will take a look at the manuals now that you raised my interest. I learn something new every day about my MH, or someone else's.

[Pigman]

Getting a tow provider to hook to the air drier may be harder than it looks at first. Since the drier is all the way in the back it requires an extended hose from the tow vehicle and also some extensive stringing to keep the hose up off the road. When we required an extended tow (over 100 miles) in west Texas with our former Diesel Bounder, the tow provider connected directly to the air system at the air tanks. He was then able to drape his air hose over a mirror and had it hooked up in seconds.

I don't know if we dodged a bullet or not, but it was a good tow with absolutely no damage. Rather than being concerned about the air, I was scared to death about the tow speed this guy was using. We hit 70 mph twice, once on the way up and once on the way down. (LOL) But as I said, no damage at all and we sure got to a Freightliner facility in record time.

John

[wagonmaster2]

Being towed is one of my biggest fears about owning a diesel MH, next to breaking down in a place with no cell phone service. Can't imagine driving a MH 70 MPH let alone towing one at that speed.

Wagonmaster2
2004 Meridian 36G

[J Walker]

A look at my 2000 XCS Freightliner chassis manuals revealed that they specify pressurizing from an "external" source using the schrader valve. They don't say the connection has to be maintained while towing. I have no shrader valve in the front of my MH or at the air dryer, but I have a quick connection on the front firewall. I have not checked near the air tanks but I don't recall seeing a shrader valve. I don't know if I could pressurize from the front connector, but I am sure there is some way to add pressure somewhere.

[Pigman]

Quote:

Originally Posted by J Walker A look at my 2000 XCS Freightliner chassis manuals revealed that they specify pressurizing from an "external" source using the schrader valve. They don't say the connection has to be maintained while towing. I have no shrader valve in the front of my MH or at the air dryer, but I have a quick connection on the front firewall. I have not checked near the air tanks but I don't recall seeing a shrader valve. I don't know if I could pressurize from the front connector, but I am sure there is some way to add pressure somewhere.

I think Troubleshooter clearly pointed out that the under hood connection can NOT be used. Also, I doubt anyone would want to tow a rig any appreciable distance without a source of air for the suspension and emergency brake release. Rolling down a highway at speed and having the rear wheels lock up is NOT a good thing. The tow driver will know where he usually hooks up and will do what is necessary. They do not like law suits any better than any one else.

John

[Gary RVRoamer]

The tow instructions will vary by chassis type. The XCS chassis is substantially different than the XC.