Airbag leak- and porpoising

[bpaikman]

I don't know if any of you saw the posts I made while we were traveling through Colorado last month, but we observed the following:
1. hearing a "ch" sound every 30 seconds,
2. experiencing a porpoising effect (We manage to correct that problem by the way we handled the jacks, but it still was puzzling because it didn't do that doing our last 3000 mile trip.
3. When I drove the RV to its storage facility, my husband would follow to look for issues - and he was observing what he thought was a slight lean to one side and it seemed lower than usual toward the back.
4. We lost a rear SnapPad (fortunately under warrant) , probably on a bumpy, but carefully navigated, detour on CO 50 near Montrose. We think it's because the rear of the motorhome is riding a little bit lower than it should've been.
-----We believe found the issue. We took it in for service and they discovered a small leak in one of the rear airbags. interestingly, they told us it could still be driven as is, for some time .... uhhhh we opted to replace. And we are replacing both rear airbags at the same time.
Not a cheap repair, but it IS the first major-"ish" repair since we've had it.
Just thought this information might be interesting.
(W experienced the first symptom of this airbag leak, porpoising.... last year, 4000 miles ago, But we didn't realize what it was... we thought it was operator error. But we did wonder why we didn't experience it for the first 2500 miles).
(Porpoising, or rabbiting, as I call it, Is when the motorhome leaps and jerks forward like a porpoise, and you realize what it would be like without air bags. We corrected the issue by putting the jacks down and taking them up again. We observed that the air pressure has to be maintained above 75 psi before starting off, and preferably 122.5 psi, which it will reach within a few feet of travel.)
Every time we have a problem, which is probably just about every time we have a trip, we learn something new.

 

["EZ"]

The "ch" sound is the moisture ejector spitting out the moisture from the air tank. Sounds like it is working.

The "porpoising" effect is probably caused by worn shocks rather than your air bag system. The air bags support the vehicle and the shocks are what keep the vehicle from bouncing up and down on the air bags. Put new shock absorbers on and you'll be amazed.

If you have an air bag leak you did the right thing by replacing it and the matching one on the other side. Air escaping from your system like that will cause the air compressor to run non-stop. This will over heat the air causing additional moisture in the system. This is adding to the "ch" sound you hear every 30 seconds. It's trying to compensate. It will also waer out your air compressor.

Hope this helps!

 

[Rich W.]

Agree with EZ on all of it - your air dryer is working hence the short blast of air as it discharges moisture. If that filter (desiccant) is over three years old you should change it, especially since it might have been working overtime ever since you had the air bag leak. Also do you drain your air tanks regularly?

On shocks mine are 6 years old with 50k miles. They probably are still good but Id say new shocks are in my near future. Not sure if I’ll stick with OE or go with something else. Im satisfied with the ride right now. I read a good tech tip lately on checking your shocks: use a temp gun and take the temp of each shock after driving for about 30 minutes. If one or more are at a noticeably lower temp than the rest, it/they are worn out. If they are all the same I guess this wont help unless they are close to the temp of the frame or axles - they should be warmer. I’d like to know what temp is “normal” for shocks in good condition.

On the jacks I’d say that was a coincidence since the systems are unrelated to each other.

Regarding air pressure, I let mine air up all the way before starting out so that I have maximum braking ability immediately.

Ride height is adjustable and has a factory spec. When I had Active Air installed, HWH had me contact FL to get the factory ride height numbers and they adjusted the final set up accordingly. So once your new air bags are in, you should have this checked too. The measurement is something like from the center of the lower shock bolt to the frame, but I dont remember exactly. FL will know. For a shade-tree ball-park check, park it on level ground and measure from the pavement to the top of the arc of the wheel wells. It should be the same side to side. Mine is about an inch lower in the front 41” in the rear, 40” in the front. This is an inexact measurement but it will tell you if one side is low.

I’m looking forward to a report on how your coach does after the air bag replacement. Being two years behind you I can anticipate what I’m facing in the near future. Along the lines of PM I had my serpentine belt replaced early (50k miles) and the water pump and idler pulley checked after reading about several premature failures. If I had a side radiator coach I wouldn't worry about it but I don’t want to have to do this job on the side of the road (or at all really) or be towed, and then taken advantage of by some local shop.

Hope this helps and keep us posted.

 

[bpaikman]

It turns out that we had a defective valve and possibly a hole in the airbag I haven't got the story on that yet. i'm not sure I understood everything correctly but the tech was telling us that's why it would help to put the jacks down and bring them back up it was forcing that valve somehow?
Their quite knowledgeable tech guy spent a long time with us educating us about several little things. He showed us how to fast idle to warm up, and talked to us
about how to use that. I'm still not real straight on that But I got the guys email and he's always happy to help.
Sorry that I'm uncertain but there was a lot of freeway noise nearby and it kept swallowing some of the guys words. Hopefully my husband caught everything because he was closer to the guy.