XC Chassis: How Long Should Air Pressure Hold?

[vicsryd]

How long should the air system on a FTL XC chassis keep pressure? My air tanks loose about 40psi (starting at 120psi) in the first 24 hours and another 10psi per day after that. After three days in storage the coach starts settling because there isn't enough pressure to keep the suspension inflated.

I did have a audible air leak in a brake line way back during the first shakedown cruise which was quickly fixed. At the time the dealer made references to "settling is normal" and so I've really not thought about it much. However, I recently saw a '04 Meridian in storage near me which had been sitting there for three weeks and the suspension had not settled. So now I'm wondering if I do have a very subtle leak somewhere.

[vicsryd]

How long should the air system on a FTL XC chassis keep pressure? My air tanks loose about 40psi (starting at 120psi) in the first 24 hours and another 10psi per day after that. After three days in storage the coach starts settling because there isn't enough pressure to keep the suspension inflated.

I did have a audible air leak in a brake line way back during the first shakedown cruise which was quickly fixed. At the time the dealer made references to "settling is normal" and so I've really not thought about it much. However, I recently saw a '04 Meridian in storage near me which had been sitting there for three weeks and the suspension had not settled. So now I'm wondering if I do have a very subtle leak somewhere.

[Cruzer]

The XC feeds it's air bag suspension via a partitioned air tank. Once the air leaves the tank it goes through some height sensing valves. These valves control how much air goes into the bags. If that particular end is low, the valve will open, allowing air to fill the bag until it is at the proper height. If that end is too high, the valve goes the other direction and dumps excess air out of that bag until it returns to the proper height. Assuming that your coach is at the proper height, there should be no settling because the height control valves stop airflow either in or out of the bags. So, even if you drain your tanks, you'll still have air in the bags.

But, this is assuming that you drove the coach and parked it as is. If you use the levelling system you'll be dumping the bags and then the valves no longer block flow to them. When at rest the Freightliner specs show a static pressure drop test of 1 PSI within 2 minutes. After 4 hours your tanks could be empty and it would be within tolerance. But, as mentioned before, your bags should remain inflated.

[vicsryd]

This occurs in storage only without jacks/dump.

I have prooper ride height (checked by FTL dealer).

If I lose height at all four wheels and lose pressure in the tanks then I have to assume some general systemic problem.

I'll put this on my end-of-season list for the FTL dealer alongside the 6 month oil change.

Thanks.

[ppeter313]

Another variable here is the number of times you go in and out of the motorhome once you've shut down the engine. The air suspension will continue to compensate as you walk around, open and close the slides, and go in and out. That's the random hiss of air you hear every once in a while.

Paul

[NHRAF145]

I have the same thing. I park my coach and in 4-6 days it is down on the bags as if I hit the dump button.

Shawn

[CaptBill]

Mine is also the same; 4 - 6 days the bags are deflated and the rig is sitting on the frame. When I called Freightliner 2 years ago, they told me that this is well within spec. I was not concerned since we would have the jacks down if we were staying in a CG, and would dump the air when the rig is in storage.