Beware of would-be air suspension mechanics

[Darl-Wilson]

I had a conversation this morning with a client, employed by NAPA, that is acquainted with several mechanics. He recommend 2 as being great with trucks/buses and air suspension. Shortly after ending our conversation "Mechanic Dan" called. I told him I was considering replacing all my air bags and the valving. I asked if he was familiar with the Prevost bus and their air suspension system. Ol' Dan told me he had worked on lots of these systems and they were all 'purtty much the same'. Then I asked specifically if he had worked on the Prevost system. Again his vague response was that he is a great mechanic and knows this stuff inside and out. He was willing to tackle replacement of the bags and valves. No Fear. I was still feeling uncomfortable with this guy so I asked him if he knew what a 'Norgren Valve' is. Silence on the other end of the line and finally a feeble, "no".

Needless to say ol' Dan will not be working on my bus or even getting close to it. If I had not attended the seminar (Ok Fly Guy John, Briefing, damn it a briefing) presented by Jon at Pahrump I wouldn't have known these things and may have hired a BS Mechanic that would have left my pocketbook and bus FLAT.

Thanks Jon and Hector for the great information. Score another one for the POG!!

[Jon Wehrenberg]

I won't defend this guy because he was clearly trying to blow smoke. But if the sole objective is to replace air bags and Norgren valves the skill level required is little more than that required to remove and replace. He will not need to know what he is doing or why he is doing it.

Air bag replacement entails locating the air bag, removing an air fitting, 4 nuts, and then reversing the procedure.

Obviously there is a little more involved, such as removing some wheels and the drive axle front fender liner, but that is the jist of what is involved.

Replacing the Norgrens is the same R&R. The difference is if the guy switches an air line by mistake. He does not need to know what the air lines do, or where they go, but he sure needs to replace them on the new valve in the exact same way they came from the old valve.

When all this is done everything needs to be leak tested. No bubbles can be tolerated.

My only concern is when a mechanic characterizes himself as knowing that they are all "purty much the same". This guy can't be trusted to not make assumptions. If he gets creative with where the lines go on the Norgrens sorting things out can be a nightmare. Personally I would rather have the apprentice do the job as long as he understood the ground rules. He will be so afraid of screwing things up he will actually take the time to mark hoses, make sketches, take photos, etc. Just like chickens like me do.

A number of POG members have now one what you want Darl. Especially your closest POG neighbor. Maybe he has some recommendations. I do know Jim repaired stuff done by "professionals" as have others.

Whoever does the work, insist they support the coach. Jim Shoen has shared with me his support techniques and they are superb. Nothing less than absolute support of the coach is acceptable.

[hhoppe]

Darl: As I have recently proven you do not take your Prevost into a shop displaying a Detroit- Allison sign out front thinking they know all the mechanics and service expertise for your Prevost. Some of them cannot be trusted to do the Detroit / Allison portion of the service. This said I reccomend we take our Detroit / Allison work to a factory authorzed dealer that can be trusted. Take your chassis, suspension service to a bus specialty shop. I have found a tour bus company that does all their own maintenence on their Prevost fleet of buses and has been doing it for over 20 years. They indicated they would welcome outside service work for my Prevost. They were reccomended by a friend that ran his own bus fleet for years. The shop is in San Jose, CA.
Front end and chasis alignment should be done by experts in the heavy highway bus and truck alighnment business. I have found two very experianced such shops that did excellent alignment on my 40' Prevost. One is located in Hayward, CA and the other in Sacramento. Anyone interested in any of the above names, please contact me. The only Detroit / Alliison dealer I have had excellent experiance with is in Springfield, Oregon. They have other sister shops in Oregon.

[dreamchasers]

I had a conversation this morning with a client, employed by NAPA, that is acquainted with several mechanics. He recommend 2 as being great with trucks/buses and air suspension. Shortly after ending our conversation "Mechanic Dan" called. I told him I was considering replacing all my air bags and the valving. I asked if he was familiar with the Prevost bus and their air suspension system. Ol' Dan told me he had worked on lots of these systems and they were all 'purtty much the same'. Then I asked specifically if he had worked on the Prevost system. Again his vague response was that he is a great mechanic and knows this stuff inside and out. He was willing to tackle replacement of the bags and valves. No Fear. I was still feeling uncomfortable with this guy so I asked him if he knew what a 'Norgren Valve' is. Silence on the other end of the line and finally a feeble, "no".

Needless to say ol' Dan will not be working on my bus or even getting close to it. If I had not attended the seminar (Ok Fly Guy John, Briefing, damn it a briefing) presented by Jon at Pahrump I wouldn't have known these things and may have hired a BS Mechanic that would have left my pocketbook and bus FLAT.

Thanks Jon and Hector for the great information. Score another one for the POG!!

Darl,

I thrilled to hear the presentation was beneficial. Jon and I worked on the functionality behind the scenes planning a roll out for the Sevierville Rally. He took the same seminar to Pharump and I have seen several great comments. If you get rusty and would like to refresh yourself on the functionality of the suspension, it is available for use 24/7. I have posted it on my website. Checkout the post previously posted with logon information.

http://forum.prevostownersgroup.com/...ead.php?t=2116

Thanks again for the comments. This tool would not have been developed without the assistance of Jon.

The exercise of developing the presentation has meant a higher level of understanding for myself of the complex suspension system. I'm glad it was useful.

Hector
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[Darl-Wilson]

Jon, I totally agree with what you wrote about having someone diligent doing this work as opposed to a sloppy journeyman mechanic. I am diligent, and like you would take care to mark everything so it goes back exactly as it came apart. I hate to admit this but I have a terrible fear of two things; one is of heights and the other is being under the bus. It is amazing I can fly steep banks around a pylon in a flimsy Cessna 150 without fear but I cannot look down the side of Hoover Dam without my feet tingling. I am able to get under a vehicle like my CR-V but getting under the bus with anything less than being in a well-constructed pit is one of my greatest fears. The death of Jim Scoggins did not make this any easier. I would love to fix this suspension like Jim Shoen but I can't so I need to hire it done. I am also heeding your advice about using someone skillful and not allowing them to rip me off.

Harry, we talked about the mechanics in CA before and I would appreciate the phone of both the Hayward and Sacramento shops.

Thanks for all the help and suggestions,

Darl

[Darl-Wilson]

Darl,

I thrilled to hear the presentation was beneficial. Jon and I worked on the functionality behind the scenes planning a roll out for the Sevierville Rally. He took the same seminar to Pharump and I have seen several great comments. If you get rusty and would like to refresh yourself on the functionality of the suspension, it is available for use 24/7. I have posted it on my website. Checkout the post previously posted with logon information.

http://forum.prevostownersgroup.com/...ead.php?t=2116

Thanks again for the comments. This tool would not have been developed without the assistance of Jon.

The exercise of developing the presentation has meant a higher level of understanding for myself of the complex suspension system. I'm glad it was useful.

Hector
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Hector, I sincerely appreciate all the time you and Jon took to make this presentation. This is as professional as anything I have ever seen. I am sure the other POGers share this same sentiment. I plan to review it again before I take my bus to the shop to have this work done.

Thanks,

Darl

[Jon Wehrenberg]

Darl,

I am sure Jim Shoen will echo my words. The tasks you want done are not difficult. Just so you are aware of what I would consider reasonable times you can use the following to determine if your service facility is being fair to you and themselves.

I would allow 12 hours for all the air bags. That is 1.5 hours each on average and that is ample time and includes pulling the wheels necessary to access the bags. Make certain the front air bag fittings get modified if you do not have IFS. Roger and I did his coach quite easily by adding a 4 1/2" nipple to bring the fitting towards the outside where it was easy to get a wrench on it. It requires a new straight 1/2" compression fitting and the nipple and the hose to get cut. I think we posted pictures and the procedure.

There are 3 port and 5 port valves on your coach. The critical thing to remember when changing them is they are to be leak free at all fittings (like the air bags) and this is easier said than done. Jim and I added the fittings to the new valves on the workbench instead of trying to do it while under the bus. I would guess it took me about 30 to 45 minutes per valve at the most. The fittings and hose connections have to be absolutely leak free.

My guess is 2 solid days of work and your bus should be done. They must use ample supports beneath the coach. I double up my supports and I recommend anybody that even contemplates changing air bags or Norgrens needs to do the same thing because the entire chassis is up in the air.

I am going to help Eric in about a week do the air bags on his bus. If the times are any different we will post it.

[Darl-Wilson]

Jon,

Harry was kind enough to email me 2 companies that he recommends to do the 'leans' work. My first question after I detail what I need done will be; how many hours? I also plan to be on the scene when this work is done and to have my laptop and air card so I can access Hector's website presentation.

I am going to wait until we take our 5th-12th of July trip to Lake Shasta before contracting this work. Other than crawling under the coach is there any check or simple, temporary repair I can make to slow my leaks?

I thought not!

Thanks for all your advice.

Darl

[Jon Wehrenberg]

Darl,

You are on the right path changing air bags and Norgrens.

It will cost you more in time and money to chase leaks and diagnose them than it will take to just replace the aging parts.

The key to success however is to have the mechanics verify every fitting and component is leak free. As they replace the parts in a section (Front, LH, RH) they can air up the system and soap the fittings. No bubbles! It must be bubble tight.

Give me a heads up when you will have the work done and I can be sure to be available if you run into any problems. Having Hector's program will help you understand exactly which components (and only which components) are going to contribute to problems if any show up. To prevent having to pay for shoddy and careless worksmanship I would suggest you get an agreement that you will pay for the job to be done right, but will not pay for time spent finding problems to repair the work.

Jon

[rfoster]

Jon your comment regarding "bubble tight" reminds me of the Sevierville Seminar. Hector mentioned a bubble tight test that he used thru the years in the refineries if I remember correctly. Now that being said I don't remember all the details of the device.

Hector - can you help me out here and post a refresher of the bubble tight tester. I don't need it at present, but - but sooner or later I will.

Thanks again to both of you for an excellent presentation at Sevierville.