-
Front end of coach slow to “air up”
Arrived Indianapolis with the coach at midnight Tuesday night/Wednesday morning. Used the Level Low system to Dump the air so it was easy to get in and out of the coach.
It was 17 degrees this morning (Sunday). Fired up the coach, set the Level-Low system to “Ride” which should have brought the coach up to “ride height”. Had to idle the coach for quite a while to warm it up. The rear of the coach came up in a reasonable amount of time, but the front end took forever. In the past when it was slow to rise, I’d noticed that releasing the parking brake and putting the coach in drive, it would sometimes come up a little and continue to very slowly rise. I played with the “ride-auto-manual” switch to try to raise it manually, but that didn’t didn’t do any magic.
This morning it was taking forever. Finally the front mud flaps were off the ground so I repositioned the coach from the back-in camping site to a blacktop parking lot to hook up the car; it came up a little more. Finally after I hooked the car up the front end was up high enough that I could drive away.
Went about 50 or 60 miles up I-65 toward home and stopped at a rest stop; the coach was “up” now all the way. So the air system was capable of raising the coach all the way. Cathie mentioned that she “thought” he could hear air escaping/air leak below feet while in the passenger’s seat.
Why does could it take so long for the coach to come up to ride height? I don’t completely understand how the system works, but I’ve come to understand there is a “ride height valve” that I wonder if it’s “sticking” and not telling a (Norgren?) valve to put more air in the front airbags so the coach rides higher.
I’m assuming that as soon as the air system has built up enough pressure (like for sure 120#) that there would be an enormous amount of air available to pump up the front airbags. Maybe the line that controls the Norgren valve or the line from the Norgren valve to the front airbags has a leak or maybe is pitched and air flow is restricted; but I’m just guessing. Of maybe the ride height valve is sticking and now working right.
It seems to me this issue is exacerbated when its cold out. It if were warmer I’d drive the coach up on some wide boards, properly support the front of the coach, and then crawl under it to try to follow the plumbing; but its not.
We’re headed to ETLC at the end of the month and this is beinging added to the list, but I’d like to try to figure out what the problem is before we get there.
-
15 Replies
-
Add some more information because even with information provided it gives no real clues other than it takes time.
Do all pressure gauges come up to full system pressure in what is the normal amount of time?
Can you hear the air dryer purge often as the front is trying to rise? By often I mean the normal amount of time between purge cycles?
You mention cold temps but don’t say if this started since the temps got cold which could be coincidental or a clue.
How often have you been running the aux. compressor prior to the cold temps and how have you been preventing moisture from entering the accessory tank. The Liberty “spitter” is not the best protection against moisture.
-
I would bet there is moisture in the system affecting a Norgren or ride height.
-
This might be a good opportunity to remind everyone that when the temps get below freezing moisture in the pneumatic system can prove to be a serious concern.
Most of the components in the chassis are exposed to the outside temps and those with moving parts could stop working as required. A pre-trip brake inspection becomes important because if check valves or protection valves are affected safety is compromised.
If the moisture is in the accessory system everything else can be affected especially the suspension because Norgren valves in particular will just stop working.
We stress the importance of proper pneumatic system maintenance and with sub freezing temps that advice takes on a significant meaning.
-
Dick, from what I hear from folks, it is normal for the front to raise slower than the rear. There are only 2 airbags raising the front, and there are 6 raising the rear. I bet the normal ride height pressure in the front airbags is higher than the rear?
Does your bus have an accessory system pressure gauge? Mine didn’t. I installed one in my dash and another in the steer compartment so as to know what’s going on with the level system air, etc. The more the accessory system leaks, the longer it takes to air up.
Here is a link for the gauge install
https://prevostcommunity.com/forum/threaddetails.asp?Category=&ThreadID=6196
-
Jon asked: Do all pressure gauges come up to full system pressure in what is the normal amount of time? Yes. After starting the Detroit the two gauges on the dash come up to 120# in a reasonable time and hold pressure.
Can you hear the air dryer purge often as the front is trying to rise? By often I mean the normal amount of time between purge cycles? I hadn’t listened for that, I’ll do a test today and listen. If I understand correctly how the air dryer purge works, more often is better than less often; correct?
You mention cold temps but don’t say if this started since the temps got cold which could be coincidental or a clue. Its often slow when its warmer (50’s/60’s) as well, but not like it was Sunday. Sunday was probably the slowest.
How often have you been running the aux. compressor prior to the cold temps I run the aux compressor to run the toilet when we’re parked and the pressure in the system drops. I noticed that sitting in the coach in the evening (temps low 30’s, hi 20’s) with the aux compressor on, the compressor ran more often than in the warmer temps.
and how have you been preventing moisture from entering the accessory tank. How would I do that? What actions can I take to keep that moisture out?
The Liberty “spitter” is not the best protection against moisture. Is there a better option that I should consider installing?
Don asked: There are only 2 airbags raising the front, and there are 6 raising the rear. I bet the normal ride height pressure in the front airbags is higher than the rear? That tends to make sense to me, but I have no way of determing those pressures and possible delta.
Does your bus have an accessory system pressure gauge? Not on the dash, just in the steering bay. Mine didn’t. I installed one in my dash and another in the steer compartment so as to know what’s going on with the level system air, etc. That sounds like a good idea, I’ll consider that. I like more gauges than less so I can see what’s going on. The more the accessory system leaks, the longer it takes to air up. That certainly makes sense to me. If the aux compressor runs more often in cold temps, that points to a good sized leak or more leaks … leaking air can’t get into the air bags to raise the coach.
Thanks for the advice and comments.
-
Dick,
My coach responds quickly in the manual mode. So If I want to make sure that I am at a proper ride height in front. I can go to Manual and toggle raise front enough that I am above ride height in just a few seconds. Then toggle back to road, And she will settle back down to proper level. The aux compressor will pump a lot of moisture into the system. And I agree the spitter is junk. Any good separator unit placed directly downstream of the aux compressor will do wonders. I placed one with a Auto drain option. And have a clear transport tube run down into a small juice bottle just to see how much it would catch. I plan on running it thru the bottom of the bay eventually where it will drain onto the ground. It has caught enough in the last couple of months to fill a shot glass. Moisture and freezing temps will not be a good combination.
-
With the little more information provided I have some comments and opinions regarding where I would look for the problem.
First add an accessory air gauge if you don’t have one so you have a place to read that system. I installed mine on my 97 coach on the manifold in the steer compartment. It obviously was not visible from the dash, but when I needed to know the pressure I could open the door and look at the gauge. My XLII has a dash mounted accessory pressure gauge.
If you run your aux compressor unless you have a working trap, dryer or other device to remove moisture from the accessory system you are putting water into your accessory tank and devices. I used the word “working” because whatever device is downstream from the aux compressor has to work or it is not protecting the system.
With all the air system issues your coach had when you bought it I think you realize how critical maintenance on the system is. Drain the tanks as often as someone gets under the coach. Service the air dryer and make sure you protect the system at the aux compressor supply side also.
I am guessing but if you have not been routinely trapping moisture from the aux compressor you may have some suspension valves that have been exposed to moisture. That starts a downward spiral because the aluminum bodies in the Norgrens start to corrode and as the spool shifts back and forth it wipes the minute surface corrosion from the spool but that sludge that builds in the presence of moisture remains in the valve body eventually making the spool more and more difficult to slide with the air pressure from the 5 valve manifold valves.
If there is moisture in sub freezing temps the sludge just freezes and the spool inside the valve will not shift or will shift very slowly impeding air flow to the suspension system.
So my guess is you have or have had moisture in the accessory system and if that is not the sole cause of the problem it is contributing.
The front on almost all coaches is slow to rise compared to the rear. The rear takes three times the air volume, but raises the coach at a lower pressure. I measured the pressure to raise the rear of one of my coaches to the ride height and it was about 70 PSI. On the same coach the pressure required for the front was about 100 PSI. Obviously air is going to flow a lot faster if it is met with less pressure so the front is going to take longer. With a full air system on my coach I can come to the ride height in the front in a couple of minutes. If you want to help the front get up faster, lift the tag, but in your case all that will do is mask your real problem.
-
Rocky: I tried that, didn’t seem to make a difference. What kind of a device did you get? Where did you get it?
-
Dick, my bus had 1 SMC brand water separator, to keep moisture from traveling from the aux compressor into the accessory system. I added a 2nd one.
Here’s a thread. -
Jon. “If you want to help the front get up faster, lift the tag” Can you expound on the how and why of this statement? I know how to lift the tag but how does doing so speed the lifting of the front. Also, could/should this procedure be used when leveling the coach?
-
Lifting the tag puts more weight on the drives and unloads the front enough to make raising easier. I use it all the time in a nose low situation and then air it back up when level.
-
Don: Thanks for that link. The big button on the side, what is that for? Push the button and the moisture/water that the device has taken from the aux air system gets squirted out the bottom? Is that how it works?
I notice the manufacturer’s description says it removed water, but not moisture. That confuses me.
-
Dick, that’s not a button, it’s a sight window. To drain them unscrew the fitting at the bottom and let the water drain out the drain tube, then screw it closed until moisture can be viewed in the sight window again, then repeat.
-
From the mfg’s site:
Water separator can remove water droplets, but it cannot remove moisture.
I think that just means that the water has to condense by means of cooling the air before it can be removed. The same principle that we see on Garage Journal with the switch-back air line setups with the ball valve at the bottom of each leg before a spitter/dryer.
-
BD: Thanks for noticing and correcting my transposition. Sounds like the “moisture” must condense to liquid water before the device will remove it. I’ll add one or two of these when conditions permit. Thanks!
Log in to reply.