2004 Freightliner XC Air Suspension Question

[cetmanhd@verizon.net]

I purchased a 2004 Winnebago Journey36G on an XC chassis. The coach has the Neway air suspension system. My question is - are the air suspension bags supposed to bleed off when the coach is turned off, all by themselves? The air suspension takes about a half day and drains itself. I would expect it to stay pressurized until I hit the dump button. Should I be checking for leaks?

[willtory]

Air systems are notorious for leaks. I would not be concerned about slight leaks in the air bags, but leaks in other air system components may cause concern. To determine if your system is functioning normally, perform the system test. It was published in a past FMCA magazine, and you should be able to locate it using the search function.

[wolfe10]

While it may be acceptable (in terms of both safety and manufacturer's tolerances) for the system to leak down in half a day, there is no reason that you can not try to identify and correct this slight leak.

After safely installing jack stands or comparable, crawl under with some kiddie bubble solution or even dish washing soap solution. Apply some to each fitting and valve-- a tooth brush (NEVER your own) helps apply it to hard to reach places. If you see bubbles, you have found the leak.

Brett

[Guest Wayne77590]

Brett is absolutely correct about the toothbrush, and everything else. I always use Earlene's toothbrush for cleaning things. I just have to remember to put it back on the charger. Great for those chrome rims and the potty.

I'm so fortunate that I live very close to Brett. (Not fortunate for him.) I've only had to ask for his personal help one time when my wife heard a hissing noise when the engine was turned off. With my "selective" hearing, I could not hear it, and she could only identify that it was coming from the drivers side. Brett climbed under the dash and was able to identify it as one of the lines going to the gauges.

I also had your problem in that after a few hours the air system would be depleted. When the crack in the line got so that it could be heard, it was discovered. A call to Freightliner identified this area as a problematic area and the fix was to replace the entire air gauge module. It was fixed under 2 year Freightliner warranty and now holds for a few days.

Good luck.

[cetmanhd@verizon.net]

Thanks all. I crawled underneath and realized the hissing was coming from one of the leveling valves. I could put pressure on it and it would release air from the rubber vent tube. If I used pressure the opposite way it would stop. So that must be some of the hissing and settling of the coach. As we unload at home we are walking in and out possibly causing the coach to sway side to side and the valves release air so it settles faster over time.

I timed the suspension bleed down so I was more accurate. As long as no one enter the coach to cause a rocking which would then bleed from the leveling vent tube, it stayed pressurized for about 24 hours. That is based on the dash brake gauges and the under the hood aux air port gauge. I may still check with a soapy solution. Another item - why is there only one leveling valve on the front drivers side and two on the rear of this coach?

[wolfe10]

Three leveling valves (two on one axle and one on the other) is common. Yes, there are exceptions such as Gary Jones designed chassis such as Alpine/Peak.

And the ride height valve should vent if it senses "too high". As long as there is no air leak in the "neutral" or in the "too low" position, all is normal.

Brett

[harrysusa]

If I replace the 13 year old air bags on my XC chassis, will it ride any softer?

Harry Salit

[garykd]

Hi Harry,

I doubt new air bags will make your coach ride smoother. The PSI in the bags along with the ability of air to move out of and into the bags as you travel can have a lot to do with the smooth ride. Shocks also play a large part in the smooth ride. For me, I'd get some advice on a shock that will provide a softer ride.

I do not mention tires as the OP did not mention vibration, which could be a tire problem.

[wolfe10]

The PSI in the bags along with the ability of air to move out of and into the bags as you travel can have a lot to do with the smooth ride.

Let me expand on Gary's statement.

The ride height valves control ride height by adding/subtracting air from the air bags, which raises/lowers PSI in the bags.

As I post frequently, ride height is critical for proper ride and handling. Too low and the suspension bottoms out. Too high and the bags are over-inflated and stiff.

Brett

[harrysusa]

HI,

I am just trying to find some relief.

The ride height has been checked by Freightliner & Redlands Truck Service and both say that "it is within specs", and the numbers they gave me confirm that.

I tried the FSD Konis & that did not help.

Bilstein tells me that there is a 15% softer shock then what comes on the coach, It is BD5-2545 & 2546, does any oe have experience with these?

Thank you,

Harry Salit

[wolfe10]

Harry,

When you say ride height is within spec, how far from IDEAL is it?

And on the axle with two ride height valves, if spec is, say, 10" plus/minus 1/8", raising the light side (from 4 wheel position weighing) 1/8" and lowering heavy side 1/8" helps a little with balancing loads. Do NOT go outside specs in an attempt to balance side to side imbalance by changing ride height.

Brett

[harrysusa]

Hi Brett,

For the front Freightliner says 10" +/- 0.25". Redlands measured 10.25" on both sides.

For the rear they say 9.375" +/- 0.125". Redlands measured 9.50". I guess I should have told them to drop them to the low side of spec but the mechanic did not suggest that.

Last time I had it wighted was in 2006 by RVSEF, RF 3825 lbs, LF 3800 lbs, RR 6875 lbs, LR 6750 lbs. I am sure it has changes some over the years but not drastically. I even tried 80 gls of water & 90 gls of diesel last time out & it still rode rough (and that was with Konis !).

What do you know about the softer Bilsteins?

Harry

[wolfe10]

Harry,

You are very close in left/right weight distribution, and on ride height, so I don't think you have a problem there.

And I have not driven a coach with the softer Bilsteins, so I can't comment. But clearly, going from a stiffer Bilstein to softer one would give an improved ride. But, that really doesn't help when comparing shocks by different manufacturers.

Brett

quote name='harrysusa' date='Apr 26 2010, 04:19 PM' post='7331']

Hi Brett,

For the front Freightliner says 10" +/- 0.25". Redlands measured 10.25" on both sides.

For the rear they say 9.375" +/- 0.125". Redlands measured 9.50". I guess I should have told them to drop them to the low side of spec but the mechanic did not suggest that.

Last time I had it wighted was in 2006 by RVSEF, RF 3825 lbs, LF 3800 lbs, RR 6875 lbs, LR 6750 lbs. I am sure it has changes some over the years but not drastically. I even tried 80 gls of water & 90 gls of diesel last time out & it still rode rough (and that was with Konis !).

What do you know about the softer Bilsteins?

Harry

[Avalanchediver]

How dificult is it to change my Neway suspension air bags? They look good overall but each has a couple areas of rubber cracking around the base when inflated. How do I know when they need to be changed out. I am pretty mechanical and would like to do the work myself if it is reasonalby easy.

Thanks,

Eric

[wolfe10]

Eric,

Welcome to the FMCA Forum.

How old is your chassis?

Like tires, air bags can have small cracks and still be 100% serviceable.

There are a number of 15+ year old coaches with original air bags.

Brett

[bhalldorson]

I also have an issue with a 2008 Freightliner air suspension system.

Following the owner's manual instructions, I lower the coach before leveling when we stop for the night. The next morning after the air suspension fills, the air pressure does not build up and the low air alarm remains on. I few times when this has happened, I could correct the problem by turning the ignition off, then restarting the engine and the compressor would start filling. However, 2 weeks ago when it happened the air tank would not refill even after I bled the tanks to zero. I called Freightliners help line and after some trouble shooting routines they sent a non-Freightliner mechanic (I was in the middle of nowhere Texas on Sunday) who bypassed the dryer. After about 10 minutes the tanks started to fill to normal pressure. We started back to Omaha (with the dryer bypassed, but the next morning it gave me the same problem, and again the morning after that. Both times I stopped and started the engine and it started working.

I first had this problem last fall and immediately took it to the Freightliner dealer who kept it for 3 days and could not duplicate the problem. Stored it for the winter, then started for Texas and spent 2 weeks on the road before the problem resurfaced. Today is day 2 at the Freightliner shop and they are telling me again that they can't duplicate.

Any ideas? The chassis is on it's last year of warranty, but since Freightliner can't find the problem, the trouble shooting labor is coming out of my pocket.

[wolfe10]

If the air compressor is working properly and air pressure does not come up, there has to be a massive leak.

It could be a dump valve hanging up, air dryer, etc.

The other possibility is that the governor that controls the air compressor is sticking and not calling for the compressor to operate.

If you can not hear an air leak, consider replacing the governor-- they are not expensive.

Brett

[bhalldorson]

Thank you Brett!! I've been all over this thing listening for air leaks and they don't exist. When the problem occurs, one tank holds at about 60 and the second at normal pressure of about 130 provided I don't use any air. The governor makes sense.

By the way, this was our sixth trip to Texas, avoiding the interstate and enjoying every trip.

Bruce

[dickandlois]

The Other item to consider is (are) the check valves between the primary and secondary air tanks.

Red is Secondary air supply and Green is Primary Air Supply.

The check valves hold air in the system as long as possible so one can stop the coach safely. The check valves are set to hold a 60 to 65 lb. pressure for the air brakes to funtion.

The other item to check is the dump valve to lower the coach . Where the ride height points checked before this problem popped up?

The pressure in the Secondary tank will not go above 60 lbs. if the ride valves are open.. Been there done that...and you do not relay hear the leak.

Rich.

[wolfe10]

Bruce,

NO, if one tank goes to 130, the compressor and governor are OK-- that is all they are supposed to do.

Are you certain this is an actual air pressure issue and not a gauge/sender unit issue???

If one tank is showing 130 and you turn off the engine and hear no leaks, I would start looking at gauges/senders. Freightliner has had issues with this-- check with them.

[dickandlois]

Bruce, Brett is correct about a air module problem and Frieghtliner Chassis. The only thing I question is, you mention one reads 60 psi. Is it changing its reading up and down,or a steady 60 psi.?

The problems with the module have generally been with the gauges jumping from one reading to another.

Generally the green gauge reads the pressure for the rear brakes and the Red reads the pressure for the front brakes and the ride height controls and will often rise and fall between 90 and 120+ psi. as one drives down the road.

There have been times when the plumbing to the gauges was reversed during manufacturing or repair. This will give a proper reading for the rear brake air level that could be on the red gauge,confusing the driver.

The rear brake pressure needs to be above 45lbs. to keep the park brake form engaging.

Brett mentioned using a brush,I have used a spray bottle with success when the connections or the location is very hard to access.

Rich.

[bhalldorson]

A couple points of clarification:

1. Once the tanks have reached normal pressure, I have never had a problem losing pressure while I'm driving.

2. The only time this problem surfaces is when we prepare to leave the camp ground in the morning. Both tanks hold pressur overnight. I start the engine and let it warm up for several minutes, then retract the jacks and and move the suspension switch to "auto". The bags fill and one tank drops to about 60 and stays there. This causes the alarm to sound and I have never attempted to drive until after the alarm goes off.

3. Most instances (not all), if I turn the engine off, then restart, the tank starts to fill to normal pressure.

This is all great advise. Thanks!

Bruce

[dickandlois]

Bruce, I put together some information covering how the air system works.

I will try to attach a PDF file I put together as I struggled to understand how things worked. can not do it directly on the thread.

I sent some information to you in a privet message.

From your description of how the gauge responds. I keep thinking its a dump valve issue. Could be the dump valve for the ride height sticking or the 12 volt solenoid not closing properly. The fact that when you power down the engine and restart it generally clears the low air pressure problem in the secondary air supply loop,because the gauge reads the proper air level within a short time. Think its a sticky valve or solenoid. The other item to check is for a loose or corroded connection at the solenoid and maybe right at the auto switch in the console.

Rich.

[dickandlois]

Bruce ! I just updated some info. on my previous post.

Good luck Rich.

[dickandlois]

Bruce,

Thanks for the resent Private Message.

The information regarding the repair was interesting. I have been looking over some technical information and still have a problem getting my simple mind around it. Just keep an eye on things and keep in contact.

Rich.