Community Forums

RV Manager · 07-08-2015, 04:01 PM

While driving down I 15 suddenly lost all air pressure. Managed to get offf on to a side street. Have called for roadside help but while waiting looking for ideas as what it might be

abarkl · 07-08-2015, 04:03 PM

Could it be simply a broken belt?

Sky_Boss · 07-08-2015, 04:05 PM

When you say you lost all the air did your airbags deflate also?

What happened as this started to unfold?

Glad to see your safe!

Good Luck!

Sky_Boss · 07-08-2015, 04:12 PM

Quote:

Originally Posted by abarkl

Could it be simply a broken belt?

I have to admit this opens up a few questions for me. What happens to the whole system in a worse case scenario? Of course I would expect an air pressure alarm and if ignored the park brake to be activated. I am wondering if the air bags would also drop on there own or are they protected by check valves to isolate them?

BrianGlenn · 07-08-2015, 04:15 PM

Start up coach, rev to 1200 rpm - do the air pressure gauges show you are building pressure? If not - go outside and listen for air leaks - should be quite noticeable - air rushing from end of hose. You may have had a fitting blow off, or air hose rupture/develop a hole.

Are you pulling a toad with air connection? It may be faulty?

If nothing the air compressor on the engine may be not working correctly - governor may be faulty. That is a mechanic fix.

Brian

EDIT: as mentioned above, the air alarm should have sounded at 60psi dropping and the parking (service) brakes (spring loaded) should have come on about 40psi dropping.

Pigman1 · 07-08-2015, 04:29 PM

Listen closely in the area of your air drier. If you have a hiss there, get under and look at it. There is a purge valve on the bottom of the unit that does NOT have a wire going to it. If it's leaking, shut down the coach and when it stops hissing, tap it with a hammer or heavy pair of pliers. Then see if your air comes up. If it does press on, but you will need a new valve. If the purge valve is still leaking, pull it off and put a 1/2" pipe thread plug in it. You will need to manually drain your air tanks daily, but you can go indefinitely without the valve until you get into freezing weather.

I had just this problem a month ago on the Alaska highway. We drove almost 1000 miles until I got to Valdez with the plug in it. Tiffin sent a valve to Valdez and I replaced it. All fine now.

theroc · 07-08-2015, 05:11 PM

Quote:

Originally Posted by Sky_Boss

I have to admit this opens up a few questions for me. What happens to the whole system in a worse case scenario? Of course I would expect an air pressure alarm and if ignored the park brake to be activated. I am wondering if the air bags would also drop on there own or are they protected by check valves to isolate them?

Yes, the air suspension system is isolated. Check valves only allow air to flow in one direction.

If you keep driving once the "low air" buzzer and light are activated at approximately 60 psi, the spring brakes (emergency/parking brake) will be applied when the air drops into the range of somewhere between 25-45 psi.

I posted that video of the transit bus CDL test preparation recently in another thread. One of the tests that should be performed regularly is the "parking brake protection valve" test. This will tell you at what psi your own spring brakes will be applied. See 4:07 in the video.

https://www.youtube.com/watch?v=eYTvdGUkNac

So you'd want to do what the OP did and once the "low air" warning is sounded (at approximately 60 psi), try to get off the road as quickly as possible as once the air drops to a certain point below that, your parking brakes will automatically be applied.

JFXG · 07-08-2015, 05:45 PM

Catcoach, I know you're probably busy now with the roadside tech, but when able please clarify. Did you suddenly lose all pressure, or did the pressure gauge suddenly start to decrease? Did your low air light and buzzer activate? If you suddenly lost all pressure, how did you manage to get off I-15 onto a side street without your e-brake setting? Or did your gauge TELL you the pressure was lost, but everything seemed to
be operating normally? (I've had that happen, too) These are all symptoms that indicate failure of different components, but you have to be accurate or attempts to help will be misleading.

Fulltiming since '12
2002 DSDP 40, FL, Cat 3126

JFXG · 07-08-2015, 05:59 PM

Catcoach, I had a fairly rapid pressure loss a couple of years ago. Turned out to be a brass plug vibrated loose from the air dryer body. Depending on your specific symptoms, could be an air valve, air dryer, compressor, governor, VDC....

Fulltiming since '12
2002 DSDP 40, FL, Cat 3126

RV Manager · 07-09-2015, 08:17 AM

Update. The problem was and is the purge valve on the air dryer. I am parked at a diesel repair facility having it replaced this morning.
To answer some of the questions, I am a gauge fanatic, so as I was driving I noticed the air pressure dropping, then about the time I pulled over the low air alarm went off. At that point I had he about 65 psi but was in a very precarious spot along side the highway. Very slowly and carefully I drove to the next exit, exit 59, in Cedar City, Ut and pulled off onto a side street. By then pressure was below 60 and I was worried about the e- brake coming on at any moment. As I stopped the pressure was under 50 and the e-brake automatically applied.
By then the pressure was so low there was no noticeable Hissing sounds. Called Freightliner and they offered some suggestions, also called Good Sam.
45 minutes later Austin from Bar M diesel arrived and we began to diagnose the problem. Because I had no pressure at all it was impossible to detect a leak. Eventually we attached my air compressor to the air dryer Schroeder valve in an effort to get enough air pressure to get me to a safe place. That was when we could feel and hear the purge valve blowing air. Austin the bypassed the air dryer and the coach aired up fine.
To answer a couple of the other questions, yes the air bags slowly deflated as I was parked along side the road.
Luckily at no time did I lose total brake control, but I knew what was going to happen once I went below 48 psi, so knew I had to get to as safe as place as I could asap.
If you ever have any issues in the Cedar City/Beaver Ut area I can highly recommend Austin at Bar M .Diesel. Also even though I often complaints about Good Sam they did as advertised, provided roadside assistance and paid for the service cal and one hour of time. No problems or issues.

D Lindy · 07-09-2015, 09:07 AM

When I drove truck we carried the brass fitting needed to bypass the air dryer for just this reason. I still have the fittings and they're now in the coach parts bin.

DMTTRANSPORT · 07-09-2015, 09:20 AM

Quote:

Originally Posted by Catcoach

Update. The problem was and is the purge valve on the air dryer. I am parked at a diesel repair facility having it replaced this morning.
To answer some of the questions, I am a gauge fanatic, so as I was driving I noticed the air pressure dropping, then about the time I pulled over the low air alarm went off. At that point I had he about 65 psi but was in a very precarious spot along side the highway. Very slowly and carefully I drove to the next exit, exit 59, in Cedar City, Ut and pulled off onto a side street. By then pressure was below 60 and I was worried about the e- brake coming on at any moment. As I stopped the pressure was under 50 and the e-brake automatically applied.
By then the pressure was so low there was no noticeable Hissing sounds. Called Freightliner and they offered some suggestions, also called Good Sam.
45 minutes later Austin from Bar M diesel arrived and we began to diagnose the problem. Because I had no pressure at all it was impossible to detect a leak. Eventually we attached my air compressor to the air dryer Schroeder valve in an effort to get enough air pressure to get me to a safe place. That was when we could feel and hear the purge valve blowing air. Austin the bypassed the air dryer and the coach aired up fine.
To answer a couple of the other questions, yes the air bags slowly deflated as I was parked along side the road.
Luckily at no time did I lose total brake control, but I knew what was going to happen once I went below 48 psi, so knew I had to get to as safe as place as I could asap.
If you ever have any issues in the Cedar City/Beaver Ut area I can highly recommend Austin at Bar M .Diesel. Also even though I often complaints about Good Sam they did as advertised, provided roadside assistance and paid for the service cal and one hour of time. No problems or issues.

Air Dryer service is a must, if you come from a wet environment into the dry air of the southwest....cracks happen when it hasn't been serviced like it should.

dpinvidic · 07-09-2015, 09:25 AM

Quote:

Originally Posted by D Lindy

When I drove truck we carried the brass fitting needed to bypass the air dryer for just this reason. I still have the fittings and they're now in the coach parts bin.

Can you elaborate on what fittings are needed for this?
Is if a short hose, or just a plug?

Sounds like a good item to have.

Dan

Loren Rice · 07-09-2015, 09:34 AM

Catacoatch,

I hope that I do catch an air problem as you did. I try to watch my gauges as well, but there's always that chance where you just looked and then the event happens and you don't notice till the alarm goes off and you have much less time to react. Or it could be you happen to be driving through a particularly intense stretch of road that require your eyes on mirrors, signs and the lane ahead of you. (not unlike parts of I-5 going through LA)

I have thought about what I might do if such an occurrence happens to me. I feel I would want to do as you did, "find the nearest safe place to park it."

Your reference to good sam. Is that the auto club or do you have insurance through camping world? I am just wanting to understand which of those two gave you your satisfactory report of service.

Hope for your continued good & safe travels.

Loren