Dumping rear air bags on M2

[RonLC]

Originally Posted by JCAT

The cost for the FL Service Center to install the Dump Valves is ~ $2800 inclusive, but I believe that it might be less once they get into it.

What is Southport Truck Center doing to justify this wildly different cost?

[twc88]

Jcat

Coach drops 2 1/2” when dumped, measured at top of wheel well.

As far as leveling I am guessing it will depend on which end is high whether I dump or not. If front is high I will leave air in, if rear is high I will dump to get closer to level before leveling. In my garage which has a level floor coach levels so much better if I dump first. I assume this is because these sit tail high on a level surface. I will say, I also reset null again with it very slightly high in rear, that way it will not try to pick up front so far. Going to be trial and error I’m sure for a bit.

Ron

I believe that Freightliner is going to put in a ACM (air control module) that is controlled by switch on dash through the ECM. I know that is how I have seen it in factory service manuals.

Tom C

[JCAT]

Tom –
You have it right. It appears you have some latent knowledge and skills at work here. It sounds like your solution is principally the same as on the Cascadia – less an ECM connection, maybe. If I recall correctly, the Cascadia uses only a rocker switch on the dash to an ECM that activates the suspension dump operation. I’ll end up with a rocker switch plugged into an ECM and a “push-pull” knob like the Parking Brake on the dash. As I understand it, the ECM allows Freightliner to then program the “smart switch” on the dash to initiate additional functions related to the dump operation.

Freightliner will only install the dump valve in accordance with their engineering specifications, but if you have the skill, the tools and a place to work, I think DIY is far more cost effective and straight-forward. But, I understand and appreciate Freightliner’s position when working on a customer’s chassis air lines.

Your suspension dump procedure makes good sense given the presence of the suspension dump capability. (What do you think would happen if you dumped the air then “auto-leveled”; giving consideration to the Site slope, of course)

The coach dropping 2 ½” to 3” is what I was expecting so, glad to hear your experience.

[RonLC]

Originally Posted by JCAT

Freightliner will only install the dump valve in accordance with their engineering specifications, but if you have the skill, the tools and a place to work, I think DIY is far more cost effective and straight-forward. But, I understand and appreciate Freightliner’s position when working on a customer’s chassis air lines.

To me one of the most important considerations in allowing Freightliner to do the job is the peace of mind knowing that you did all you could to reduce the possibility of some future owner coming back on you personally if something in the system catastrophically fails.

I still think that Southport's price is excessive compared to the other (mentioned herein) Renegade dealer's prices, assuming that they are also Freightliner dealers. My selling dealer, North Trail, is a Freightliner dealer so I would guess that the other big dealers are too.

[twc88]

Jcat

Most of the info came from reading my M2 factory service manual. My system is basically the same without integrating any Freightliner electronics and doing the same thing but manually. I could essentially dump the air at highway speed, I'm sure the factory system would not allow that to happen. That is one of the reasons I picked a guarded switch, so that is less likely to happen. That same that makes the switch I used also makes a locking switch, I just didn't like the look.

(Your suspension dump procedure makes good sense given the presence of the suspension dump capability. (What do you think would happen if you dumped) the air then “auto-leveled”; giving consideration to the Site slope, of course)

Seems to work fine, just need more experience in different situations.

TomC

[JCAT]

Originally Posted by RonLC

To me one of the most important considerations in allowing Freightliner to do the job is the peace of mind knowing that you did all you could to reduce the possibility of some future owner coming back on you personally if something in the system catastrophically fails.

I still think that Southport's price is excessive compared to the other (mentioned herein) Renegade dealer's prices, assuming that they are also Freightliner dealers. My selling dealer, North Trail, is a Freightliner dealer so I would guess that the other big dealers are too.

I certainly agree about the pricing from Freightliner - Southport and NT. Both have labor rates of $139-149 per hour and most of the cost is for labor hours. In the case of Southport - I elected to wait a week so that the (2) people I wanted doing the installation would be available to do the work.

Tom is correct about the integration of the electronics controlling the operation of the dump valve; one example - as soon as your coach reaches 5mph; if the bags are not aired-up - they will automatically do so.

Freightliner/Southport will only do the installation in a manner that protects their interests and that can be serviced by other Freightliner Service Centers and dealers. Liabilities associated with vehicle manufacturers these days gets a lot of attention so, I understand the reason for their installation design - albeit expensive for sure.

What really bothers me is Renegade not spending the additional ~$200 to spec a chassis with a dump valve. Even if you don't routinely use it, a couple hundred more added to the price of our coaches is negligible.

[JCAT]

Rear air suspension Dump Valve installation completed by a Freightliner Service Center. Performs as expected.

The Procedure

After checking the Site to insure steps will not hit anything when the suspension is lowered; turn ignition to ACC - tap the toggle switch - wait for desired height then push in the black knob which prevents the air bags from re-inflating. Then level the coach with the Equalizer using either auto-level or manual.

When you are ready to leave the Site retract the Jacks - turn on the ignition and if there is sufficient air in the secondary tank the bags automatically inflate if not you start the engine and the pump begins filling the tanks with air as usual. You can not start the coach without the air bags inflating.

It appears to lower the coach 3"; more or less. The bottom step looks to be 3" from level ground when the air bags are fully deflated.

I don't see the need to dump the suspension unless the Site warrants it but, at least the capability is there if needed.

[JCAT]

This photo points to the Dash switch and Black knob:

[twc88]

Jcat

Sounds like a sweat setup, I can only dump full 2.5" or not at all. No option to go half way.

Tom c

[JCAT]

Originally Posted by twc88

Jcat

Sounds like a sweat setup, I can only dump full 2.5" or not at all. No option to go half way.

Tom c

Tom - Yes, but I had to pay someone to do the work. I have been meaning to ask you where you got you M2 Service Manual. I have learned I don't know enough about the air brake system, tanks, dryer, solenoids, etc.

[twc88]

I believe it was EBay. Was cheap money, CD about 2500 pages. I'm in graphics so I printed it to keep a hard copy in coach if I ever need it in emergency.

Tom C

[nccampguy]

Originally Posted by JCAT

Rear air suspension Dump Valve installation completed by a Freightliner Service Center. Performs as expected.

The Procedure

After checking the Site to insure steps will not hit anything when the suspension is lowered; turn ignition to ACC - tap the toggle switch - wait for desired height then push in the black knob which prevents the air bags from re-inflating. Then level the coach with the Equalizer using either auto-level or manual.

When you are ready to leave the Site retract the Jacks - turn on the ignition and if there is sufficient air in the secondary tank the bags automatically inflate if not you start the engine and the pump begins filling the tanks with air as usual. You can not start the coach without the air bags inflating.

It appears to lower the coach 3"; more or less. The bottom step looks to be 3" from level ground when the air bags are fully deflated.

I don't see the need to dump the suspension unless the Site warrants it but, at least the capability is there if needed.

Hmmm.... I want to be able to lower the rear suspension and then slowly back the rig into a garage with a fairly low header height. You said above that you cant stop the system from inflating when the engine is started? If the black knob is pushed in, wont that keep the air from reaching the rear air bags even though the tanks are filling? Am I missing something?

[JCAT]

Originally Posted by twc88

I believe it was EBay. Was cheap money, CD about 2500 pages. I'm in graphics so I printed it to keep a hard copy in coach if I ever need it in emergency.

Tom C

Tom - what year FL chassis were you able to find? Its a great idea and I will do the same if I can find a current manual. Thanks.

John

[JCAT]

Originally Posted by nccampguy

Hmmm.... I want to be able to lower the rear suspension and then slowly back the rig into a garage with a fairly low header height. You said above that you cant stop the system from inflating when the engine is started? If the black knob is pushed in, wont that keep the air from reaching the rear air bags even though the tanks are filling? Am I missing something?

The Dump Valve configuration I have would not work for your intended purpose because as soon as you start the engine the bags air-up. (The black knob will release and I am certain you would not be able to re-engage with the ignition turned beyond ACC. i.e. engine "on")

There are some owners here that have posted some good DIY Dump Valve installations that would probably work for you purpose. But what about the front of your coach - won't that be too high regardless of what you do for the rear?

John