Coach leaks down after 10-12 days

[Gary Carmichael]

This is my first Prevost am enjoying very much but that leaking down evry week or two is aggravating when parked for extended periods what do you do not level and just dump all air in the bags The Prevost shop in Goodletsville can not find the leak nor can stuart. the auxilary tank works fine after some adjustment on at 45 off at 90psi Sure do miss my jacks on the Essex. Am I doing something wrong? I level it automaticly levels fine then just slow leak somewhere I guess any suggestions (please).

[truk4u]

Gary,

Give us some idea of year and conversion?

[Gary Carmichael]

2005 Liberty h3-45 50,000 miles Just bought it in stuart this Febuary. The previous owner said he had a leak but was so small no one could find it.

[jack14r]

After you level the coach you should put the rocker switch back in the center position and turn off the ignition switch quickly.that should hold the coach level.Is that the procedure that you are using?

[Jon Wehrenberg]

I will defer to Jack's post about the rocker switch positions, but I am not sure it is necessary. On my first Liberty the leveling switches were active with the key off. The procedure to shut down after leveling was to restore the master rocker switch to the "road" position and immediately turn off the key. That is what Jack has described. What that does is restore all three Norgren 5 port valves to their normally closed position, locking air in the air bags.

On my current coach I find the only way the leveling system rocker switches are active is if the key is on. As soon as I turn the key off the Norgrens go to the normally closed position regardless of rocker switch position. Regardless, I think it is a good discipline to shut down as Jack described.

But you say your coach leaks down. That requires a more specific description. Our leveling systems are not very complex, and in fact while we may view them as a single system, they are in fact three separate systems, front, left rear and right rear that happen to share an auxiliary air supply connection. Does your entire coach settle down or does it lean. If you do a search you will see "the leans" are an issue everyone is going to deal with or has dealt with.

Tell us specifically what is happening with your coach and perhaps we can isolate the specific place or places to look and we can help with the diagnostics. As Tom suggests, add you coach info in your signature line so all reading and helping know the specific model. On suspension issues this is important because model years and converters are different when it comes to suspension issues.

[Donnie_M]

2005 Liberty h3-45 50,000 miles Just bought it in stuart this Febuary. The previous owner said he had a leak but was so small no one could find it.

I just finished up one of those "ghost, nobody could find" leaks last night! Lately, we have been seeing alot of the DOT brass "press lock" fittings starting to leak. Sometimes its as simple as removing the air line from the fitting and cutting a 1/4" off the line and reinserting. But, here lately, we have just been changing the fitting. I will attach a pic of the one we found yesterday. This pic is the Norgren for the right side. When we first started, the coach would stand up for sometimes 1 day and depending on the weather, go as long as a week before starting to lean to the right. We were at "wits" end on this till we "accidentally" pulled on the line while checking other valves and fittings and thought we heard something. We use such a thick solution, Big Blue, that it will show bubbles an hour later and all of a sudden, bubbles! It is very small but it's fixed now! At least on your H, access to these valves is very easy since all you have to do is remove the fenders. Good luck.

[Gary Carmichael]

Thanks, I level just the way you described with rocker switch back to road position and shut down engine quickly. The auxilary tank keeps air in it but the other two gauges after 10 days are at about 10-20lbs probably would go to zero if I did not crank the motor. The coach is down all over but more predominatley on the starboard side the mud flaps are on the ground! and bent back on starboard side. I thought the auxilary air compressor was interfaced with the rest of the system to automaticlly keep air in the system Troy at stuart says no, the engine controls air to the other two tanks, and does not connect to the auxilary system. Are these Norgrens you speak of some sort of check valve or solinoid valve they would not all be leaking at the same time would they? Troy told me to dump all air when parking for a long time that there is a stop so the bags are not flat, but with what you pay for these rigs the thing should work!

[Donnie_M]

I would definetely fix the main tanks air leaking. They should stay 100-120 for weeks. The most common cause for your main tank drop is the ABS valves. They tend to leak from the bottom at the dust cover. there is also a valve on each side that controls air to the "service" side of the brake chambers. These valves have a large plastic piston that develops cracks and leak.

Now for your suspension leak, the Norgrens are solenoid valves that simply switch the air source for the bags from supply air from the tank (via the level low controls) to the supply air coming from the height control valves. And actually yes they could all be leaking at the same time and one is just leaking more! Or you could have a combination of problems such as fittings as well as a valve.

Again, fix the main tank leak.

[Gary Carmichael]

Donnie where is the best place to get this work done . Stuart or Goodletsville? sounds like a pretty costly fix my 90 day warranty is gone but did have both of the these places look at the problem but as I said they could not find a problem maybe they didnot look at the right place?

[Donnie_M]

I have always had real good luck with the Prevost Service center in TN. That being said, the price of the repair will be proportional to the technicians attitude and skill level...lol It's so easy to dismiss leaks as being "too hard to find" and move on. They can be discouraging. But as I said, the main tank leaks should definitely be repaired as they can be a potential problem. Sometimes you can "cycle the ABS valves and "blow the crud out. start the engine and build full air pressure. Shut it down, hold the brake pedal firmly down, turn the ignition on and wait till all the air purging has quit. Turn key off and restart. See if that slows down the leaking from the main tanks. I will check back later.

[Jeff Bayley]

I had most of the Norgren valves replaced in search of why my bus was falling about 3 years ago at Prevost NJ. 4 days and $4,000 later they were still looking for the leak. "oh that part we changed must not be the culprit but it WAS leaking also and needed to be replaced anyway". Uh, huh. I found the leak myself while entering the bus one day. It was a leaking air plunger that worked the false floor that the converter had tied into the aux air tank. The other day the brackets came off of the same plunger and instead of mending it, I took it out and capped off the lines. I never use the false floor anyway. One less thing to leak I figure. Should have done that the first time. Anyway, you can check for a leak there maybe.

Regarding putting the leveling system in the ride position before shutting down, I have NOT been in the habit of doing that but will from now on. The process of learning on these things is something that will never come to and end. The fact that I haven't been shutting it down in the manner suggested by leaving it in the drive position probabley helps explain why I'm having issues again. We've mostly had the coach parked for the last 3 years with the exception of short trips within our home state of Florida. When I have parked it, I've leveled it and failed to leave it in the drive position before shutting down. I've noticed the coach's ability to stay level slowly erroding over the last few years. Now I think this may be the reason why. My aux air gauge is at 70 lbs right now from 120 yesterday at 5pm when we parked. That's about 17 hours to loose 50 lbs. When Prevost finished the work 3-4 years ago, the coach was rock solid and help level for a week or more. After the aux air pressure leaks down fairly low, the coach dumps (at least the rear does) in one fell swoosh of the air flushing out. I think that MIGHT be normal for it to dumb when the air get's low but maybe it's because I don't have the leveler set in the drive position and am not shutting it down right.

Is there anything that can be done for me to lubricate the new (4 years old) Norgren valves that may have spend the last few years in the wrong position while parked to tune them up ? Now is the time while I'm at Oreen Zooks shop seeing to some misc things.

[James]

I read the manual slightly different in that it appears to me that you shut the ignition off and then put the selector knob to the drive position. The paragraph out of the manual reads:

When the ignition key is turned to the "OFF"
position and selector knob to the "DRIVE"
position, the air is entrapped between air springs
and five-way three-position air control valves to
ensure the adjusted level will be kept.

[Donnie_M]

I had most of the Norgren valves replaced in search of why my bus was falling about 3 years ago at Prevost NJ. 4 days and $4,000 later they were still looking for the leak. "oh that part we changed must not be the culprit but it WAS leaking also and needed to be replaced anyway". Uh, huh. I found the leak myself while entering the bus one day. It was a leaking air plunger that worked the false floor that the converter had tied into the aux air tank. The other day the brackets came off of the same plunger and instead of mending it, I took it out and capped off the lines. I never use the false floor anyway. One less thing to leak I figure. Should have done that the first time. Anyway, you can check for a leak there maybe.

Regarding putting the leveling system in the ride position before shutting down, I have NOT been in the habit of doing that but will from now on. The process of learning on these things is something that will never come to and end. The fact that I haven't been shutting it down in the manner suggested by leaving it in the drive position probabley helps explain why I'm having issues again. We've mostly had the coach parked for the last 3 years with the exception of short trips within our home state of Florida. When I have parked it, I've leveled it and failed to leave it in the drive position before shutting down. I've noticed the coach's ability to stay level slowly erroding over the last few years. Now I think this may be the reason why. My aux air gauge is at 70 lbs right now from 120 yesterday at 5pm when we parked. That's about 17 hours to loose 50 lbs. When Prevost finished the work 3-4 years ago, the coach was rock solid and help level for a week or more. After the aux air pressure leaks down fairly low, the coach dumps (at least the rear does) in one fell swoosh of the air flushing out. I think that MIGHT be normal for it to dumb when the air get's low but maybe it's because I don't have the leveler set in the drive position and am not shutting it down right.

Is there anything that can be done for me to lubricate the new (4 years old) Norgren valves that may have spend the last few years in the wrong position while parked to tune them up ? Now is the time while I'm at Oreen Zooks shop seeing to some misc things.

The leak on the step platform should not have any effect at all on the coach leaning when turned off in the drive position. You should beable to completely dump ALL tanks and the coach stand up.

[Jon Wehrenberg]

James, Not all bus leveling systems are alike. The Liberty has a different set of controls.

Gary, You are dealing with several unrelated issues and everybody that responds has to understand there is not going to be a silver bullet to address your issues. I strongly disagree with taking a converter related problem to a Prevost facility and my reasons will be apparent if you want to manage your coach repairs. Note, I did not cay you have to do the repairs, but before you open your wallet at a service facility for someone to vacuum out its contents, please recognize you can get an understanding of your bus a little and get the service personell to concentrate their efforts where the issues might be.

The brake system leaks are Prevost areas of responsibility. You can invest thousands chasing those leaks or you can find and correct them over time. If they take a relatively long period to go from max pressure down to 20 or 30 the leaks are small, and there may be one or multiple leaks. Remember, the only place a tech should look is only those places that have pressure when the bus is parked. Your brake chambers at each wheel have zero pressure until you release the parking brake or use the service brakes so have the techs concentrate only on the pressurized portions of the primary and secondary braking systems. If they are going down simultaneously that focuses the attention to only those parts of the system that are shared. I don't remember which is which, but one brake system is for the rear and the other the front. If they do not leak down simultaneously focus on the system leaking fastest.

There are many ways to check for leaks and a good tech will use all that make sense. They are to listen, use a stethoscope, use soapy water and look for bubbles and use an ultrasonic leak detector. A tech may need to use all four depending on where the leak is and how fast it is leaking. You cannot hear slow leaks easily. If all else fails fill the system with freon and use a freon leak detector.

Now the suspension is a different animal. Make sure you understand this. The amount of air pressure in the auxiliary and primary and secondary air systems in you bus has absolutely nothing to do with whether you bus leaks down, settles down or leans. That bears repeating. When you level the coach and shut down the engine and the aux air compressor, you can bleed all the air from the three systems and the bus should not move. It should not go down or lean. When you lock the air in the air bags by shutting down the bus you are blocking the path for air to or from the air bags. In the front, if the air bags are losing pressure and the front settles, on your Liberty the leak is only going to be in the air lines to the air bags from the Norgren five port valve (not the solenoid valves), or the five port valve itself which can leak in several ways, or the three port valve for those air bags. The air bags could also be leaking (good luck finding those leaks).

The rears are almost as simple. with the addition of a three port valve in between the drive and tag axles being another potential leak source. Liberty does not have a commone three port exhaust valve so the leak in the rear could actually be at one of the electric three port valves in the steer compartment.

My point is if you do some research and provide detailed information about how your air appears to leak down, and in what order the leakage occurs we can likely make some educated guesses as to areas to look.

One point I think needs to be cleared up. Your aux air system is provided with pressure by the bus, but only after the brake systems are satisfied. Up until around 75 PSI the brake systems only get pressure, after that the aux air starts to receive pressure and its rate of pressure tracks the brake systems. The aux compressor will only provide air to the aux systems and it will not back flow into the braking systems.

[Donnie_M]

James, Not all bus leveling systems are alike. The Liberty has a different set of controls.

Gary, You are dealing with several unrelated issues and everybody that responds has to understand there is not going to be a silver bullet to address your issues. I strongly disagree with taking a converter related problem to a Prevost facility and my reasons will be apparent if you want to manage your coach repairs. Note, I did not cay you have to do the repairs, but before you open your wallet at a service facility for someone to vacuum out its contents, please recognize you can get an understanding of your bus a little and get the service personell to concentrate their efforts where the issues might be.

The brake system leaks are Prevost areas of responsibility. You can invest thousands chasing those leaks or you can find and correct them over time. If they take a relatively long period to go from max pressure down to 20 or 30 the leaks are small, and there may be one or multiple leaks. Remember, the only place a tech should look is only those places that have pressure when the bus is parked. Your brake chambers at each wheel have zero pressure until you release the parking brake or use the service brakes so have the techs concentrate only on the pressurized portions of the primary and secondary braking systems. If they are going down simultaneously that focuses the attention to only those parts of the system that are shared. I don't remember which is which, but one brake system is for the rear and the other the front. If they do not leak down simultaneously focus on the system leaking fastest.

There are many ways to check for leaks and a good tech will use all that make sense. They are to listen, use a stethoscope, use soapy water and look for bubbles and use an ultrasonic leak detector. A tech may need to use all four depending on where the leak is and how fast it is leaking. You cannot hear slow leaks easily. If all else fails fill the system with freon and use a freon leak detector.

Now the suspension is a different animal. Make sure you understand this. The amount of air pressure in the auxiliary and primary and secondary air systems in you bus has absolutely nothing to do with whether you bus leaks down, settles down or leans. That bears repeating. When you level the coach and shut down the engine and the aux air compressor, you can bleed all the air from the three systems and the bus should not move. It should not go down or lean. When you lock the air in the air bags by shutting down the bus you are blocking the path for air to or from the air bags. In the front, if the air bags are losing pressure and the front settles, on your Liberty the leak is only going to be in the air lines to the air bags from the Norgren five port valve (not the solenoid valves), or the five port valve itself which can leak in several ways, or the three port valve for those air bags. The air bags could also be leaking (good luck finding those leaks).

The rears are almost as simple. with the addition of a three port valve in between the drive and tag axles being another potential leak source. Liberty does not have a commone three port exhaust valve so the leak in the rear could actually be at one of the electric three port valves in the steer compartment.

My point is if you do some research and provide detailed information about how your air appears to leak down, and in what order the leakage occurs we can likely make some educated guesses as to areas to look.

One point I think needs to be cleared up. Your aux air system is provided with pressure by the bus, but only after the brake systems are satisfied. Up until around 75 PSI the brake systems only get pressure, after that the aux air starts to receive pressure and its rate of pressure tracks the brake systems. The aux compressor will only provide air to the aux systems and it will not back flow into the braking systems.
Jon are you sure this holds true for XLII's?

I have attached a diagram of the air system that will fit the "OP" coach. By following this diagram it makes life quite simpler. There are a few differences between Jon's 97 XL and XLII's. The XLII has 2 24v solenoids that allow primary and secondary air to fill the aux tank (if they are full) as soon as the key is switched on. H's are the same, Pretty much from 1998 to "op" 2005 and this diagram will work.

[Donnie_M]

While were at it, here's an XLII diagram

[Donnie_M]

One more important thing to note and I will let this alone...lol. Try to use a fluid designed for spraying for leaks. This will serve a couple factors such as, not corroding the brass and will continue to "suds" long after you spray so a small leak can be located. And as far as freon in the air system, PLEASE be careful as to what type you use as R22 attacks rubber...just ask all the converters who "swung" out the forward Cruise Air and used rubber lines.

[Gary Carmichael]

Donnie I have cycled the ABS valves from full pressure to none three times will let it set a couple days see what happens thanks

[Donnie_M]

Donnie I have cycled the ABS valves from full pressure to none three times will let it set a couple days see what happens thanks

I'm not sure I understand your sequence ?1. Make sure the main tanks are full 2.while depressing the brake pedal to the floor, turn the ignition key to the "on" position. You will hear the valves start "spitting". When they are finished, turn key off and release brake. Start coach and fill tanks. Note the time you shut it off and the air pressure reading on the gauges. It is a long shot, but I have had some success with this.

[Jon Wehrenberg]

Donnie,

The aux system will never receive air if the brake systems are blow a specific pressure. I think it is around 75, but may be more or less.

That way if you have a large aux system air leak your bus will continue to have brake system pressue. And if the aux system supplies air to the brake system something is wrong also.

[Donnie_M]

Donnie,

The aux system will never receive air if the brake systems are blow a specific pressure. I think it is around 75, but may be more or less.

That way if you have a large aux system air leak your bus will continue to have brake system pressue. And if the aux system supplies air to the brake system something is wrong also.
You are correct, there are pressure protection valves on the primary and secondary tanks. I'm just making the point that an XLII for some reason has 24volt solenoids so that if the main tanks are up and the aux tank is empty, you simply turn the key on and the aux tank will fill to the level of the main tanks. This is different than XL's and H's.

[michaeldterry]

While were at it, here's an XLII diagram

Donnie - do you by any chance have one of them thar fancy drawins that would match up to my '96 (95 chassis) XLV conversion? :)

[Donnie_M]

Donnie - do you by any chance have one of them thar fancy drawins that would match up to my '96 (95 chassis) XLV conversion? :)

Ask and ye shall receive!

[GDeen]

Ask and ye shall receive!

I ran a copy of that one off a few months ago ~ 36" x 60" on our large office plotter. It is taped to the wall in my bus barn and stares at me every time I am in there saying "learn me." So far, I haven't had the fortitude to dive in and start tracing all that stuff out although I know I should.....

[Jon Wehrenberg]

Everybody just needs to remember that the pneumatic diagrams provided by Prevost end with the converter connections.

At that point on the aux system (which on the Prevost is the suspension, engine belt tighteners, front door lock, early model windshield wipers, etc.) the converter adds its own pneumatics. And what may be applicable for a Marathon or a Vantare may bear no relationship to a Liberty or a CC or a Parliament or Millennium.

And the suspension controls and valving to provide the leveling feature is not going to be the same for a Liberty for example, but it may be exactly right for a Royale.

[truk4u]

After the aux air pressure leaks down fairly low, the coach dumps (at least the rear does) in one fell swoosh of the air flushing out. I think that MIGHT be normal for it to dumb when the air get's low but maybe it's because I don't have the leveler set in the drive position and am not shutting it down right.

Jeff,

That doesn't make sense for a 96 chassis year. Mine is older, 93 chassis and does dump the tag when the aux air gets lower than 60 psi. It's a PIA, but not worth the 2,800.00 for Prevost to "reverse the tag logic", 9614-A. I thought they did away with the tag dump after my 94 vintage Liberty.

Jon?

[michaeldterry]

Ask and ye shall receive!

Thanks Donnie! Now I just wish I could read French! :o

[Donnie_M]

Thanks Donnie! Now I just wish I could read French! :o

Ha! Ya know I have been tracing out that diagram for years and never realized it was all French!