Bag, valve or fitting?

[jelmore]

There's a leak in the left rear when it gets cold. Above 60°, it's solid. In the high 40s it's slow, as much 1/4" per hour. In the low 30s it's fast, as much as 1" per hour. The auxiliary air tank holds reasonably well unless it is below 30° and then it will leak out if the compressor is off.

Some history: Prevost Dallas looked at it a month ago. I told them it dropped only when cold. It was 65° and they found nothing except a very slow leak at a fitting on the air tank. They fixed that. I'm going back to them in a couple of days and would really like to tell them where to look. It will be cold there so maybe it will be obvious, but I'd rather give them advice than take theirs. The tech said the leak could be anywhere and the coach would drop at a random location rather than a specific corner. Didn't sound right to me.

Six months ago, Prevost Dallas replaced a couple of 5-way valves and 4 quick-fill tank drain valves back there. A year before that, they replaced a Burkett valve with a 3-way 2-position Norgren.

Anyway, I'm clueless, except for the facts. Can you help?

[Joe Cannarozzi]

Jim if the left rear is going down it HAS to be either one of the 3 bags on that side rear or their related air lines and fittings or the 3 or 5 port norgren on that corner including those related fittings and air lines, period.

If it is going down that fast should not be too hard to find.

You can very easy eliminate or confirm the 2 rear most bags and fittings by soaping them up, there is a 360 degree unobstructed view of those. The front drive bag has to be accessed by removing the outer drive tire and removing the rubber flap that shields it from the wheel well then needing a mirror to see the front half of the front drive bag.

If a tech is looking anywhere but that left rear corner he is wasting your money.

The accessory air leak needs to be addressed but is an unrelated problem and is not why the left rear is dropping.
.

[lewpopp]

Hey Joe,

Have you got that Blagojevich working as a mechanic? If not, he's looking for a job if you guys really want him out of office.

What a country.

[Joe Cannarozzi]

Lew I am very confused.

Usually the cook county and Illinois democratic machine politicians view the kind of stuff he is accused of as resume enhancements.

Why are they throwing him under the bus

[jelmore]

If a tech is looking anywhere but that left rear corner he is wasting your money.

Well, they already did 4 hours of that. Thursday morning it should be cold. Maybe they'll gift it this time. I'll whine.

[hobobimmer]

You can read on earlier posts in the "on the level" section to explain the detail behind my advice, but it was very useful for us to raise our tag and let it sit overnight. If it stands straight, problem has to be with tag bags or fittings or lines to those tag bags. If it doesn't, it has to be the other items in Joe C's list on this thread. By narrowing our issue down to the tag bags, I spent lots more time looking in the right places. This is the way we found faulty airbag on left tag this summer. Also, soap the area of the bag just below where the metal joins the rubber at the top of the bag. Don't judge results immediately. A very slow leak will show up in a couple of hours. But, our defective bag leaked overnight in the heat of summer, not just when it was cold. If they have to replace a bag, don't drive away until you are 100% sure the new bag is not defective!!!!!!!!!!!! Odds are good it will be. You can read all about that in the "on the level" section, as well. Good luck. Hope this helps. Debbie Faires

[Joe Cannarozzi]

Good point

If the symptoms cease after an overnight with the tag up the problem is either the 3 port or the tag bag.( 225 in parts)

If it does still drop it is the 5 port or the 2 drive bags (450 in parts)

Weigh these costs against what you have already spent for the tech hunting, I think you see where I am going.

[Jon Wehrenberg]

Jim,

Good advice above. Recognize a few things so you can speak somewhat authoritatively with the "mechanics".

The air in your suspension system is "locked" in place by the corresponding 5 port Norgren valve when the ignition key is off. If you bus leans left or right or sags down in the front your search efforts on your coach are limited to the respective air bags, the fittings, the 5 port Norgren, and in the case of the rear, the 3 port Norgren between the tag and drive axles. Included in the search for possible leaks is the corresponding three port valve which serves as the exhaust point when dumping air during leveling. PERIOD.

Because you have a 2000 coach and a Liberty you have three three port Norgrens in the steer compartment that are part of the system. You also have an accumulator air tank at their respective axle positions, apparently to serve as addidtional air volume for the air bags. Their drain fitting must be leak free.

Here is some additional leak finding comments besides the ones listed above. If the 5 port valve is leaking internaly no amount of soapy solution will find the leak. Soapy solution is only of value in finding air bag, air fitting, and air drain valve leaks. Internal leaks on Norgrens require a bench test or the use of a stethoscope or ultrasonic leak detector. If the mechanics don't understand that you are paying them for nothing.

If you suspect the 5 port Norgren for example there are other ways to verify it leaks. Remove the incoming air lines and plug the ports. If it is leaking back through the valves the bus will not drop because the path is blocked with the plug. A Norgren valve can leak "sideways" past the spool and let air escape from the end caps. That is visible with soapy solution, but only if you can see bubbles. Just like trying to see bubbles due to leaks around or under the bottom can on the air bag there are some spots you will not be able to see leaks.

But let's get real.....a full set of valves for your Liberty is less than $1000 if all are bought brand new from Prevost. A full set of air bags for your bus is $1100. Allow 10 hours for all air bags to be replaced (Eric has changed one himself in less than 1/2 hour, Joe, Roger, Brian and I have all agreed an hour per air bag on average is a safe number.) Allow 1/2 hour to 3/4 hour per Norgren (you have about 10) and you are done. Spending money to have someone look for soap bubbles, especially if they are not experts is a waste. Get Joe C. to deal with it. He knows what it takes to get the job done.

[phorner]

Joe,

Looks like you can make a career of just dealing with Prevost air suspensions

[dalej]

Jim,

It was down to 0-10 degrees when we left home last winter. Our first stop for the night, I could hear the air coming out from the right rear. When we arrived in the Phoenix area the problem was solved.

When I got back home, I changed all the air bags and things were good again. My bags were made in 94, so they were in use 13-14 years.