Panel Adhesion Problems

[JIM KELLER]

Thought I would start a Thread under this heading for future research. Jon and others have entered important information under Ah, Nice Coach.

It is my understanding many XLII"s have had an adhesion problem for years before it is discovered. In fact, the problem is usually uncovered by Prevost Facilities rather than owners. The panels start leaking water behind the adhesion and runs out the bottom side. Sometimes water leaks or stains are discovered inside the Coach as evidence of the compromise. Although the Techs are willing to talk about the procedures and repairs, I think they have been instructed to not divulge information.

[ajhaig]

While our "rivet" coach is for sale, someday we would like to get another coach. I view this XLII panel issue as a huge problem and sense that XLII owners somewhat downplay the issue.

We saw several XLII coaches at Prevost in Cal. & FL. being re-skinned. I was told the it was 300 hours in labor to remove the panels and install the new ones. Then add in the cost of the parts and paint, not cheap.

When I dropped our coach off at Panterra Coach I watched two guys re-skin the rear quarter of a "rivet" coach, I was amazed at how quickly they did it.

My longer term concern about these coaches is that as these coaches age will the adhesive issue become more widespread and at what point will Prevost no longer pick up the tab?

Many XLII entertainer coaches don't have the stainless panels, perhaps this is the way to go?

AJ

[Ray Davis]

We saw several XLII coaches at Prevost in Cal. & FL. being re-skinned. I was told the it was 300 hours in labor to remove the panels and install the new ones. Then add in the cost of the parts and paint, not cheap

Although certainly not cheap, am I not correct in that Prevost is handling this as a warranty item for customers. And, I believe they are also giving an allowance to the customers to pay for polishing and repainting. It seems that Prevost is bearing the brunt of this issue, not the customer (in terms of $$)

Ray

[rickdesilva]

I wonder if they have published some sort of a technical bulletin regarding diagnosis and repair. Generally manufacturers are reluctant to print this info because it gets into the public domain. Perhaps Prevost could make some sort of a policy statement for us.

[Jon Wehrenberg]

I have several comments to make, none of which are worth much.

For decades aircraft have used bonded construction. Adhesive bonding has been used on military, commercial and general aviation applications. Planes see more temperature extremes, and thus more movement of the affected parts than a bus will ever see. Why is Prevost having issues? Did they try to re-invent the wheel?

The bonding problem could be for a variety of reasons, or even combinations of reasons. The wrong material could have been selected. The engineering could have been faulty and the surfaces to be bonded should not have been bonded, such as two surfaces or materials that expand at different rates as temperature rises. Or there could have been a faulty manufacturing process. Is there a vintage coach that Prevost used as a test mule running around out there with bonded side skins that has no bonding problems or did Prevost just stick what they thought was a good idea out into the market to allow owners to be part of a massive field test?

Do seated coach operators have a bonding problem on their XLII coaches? If not, why not. At one time the word on the street was Prevost had no problems except those caused by converters that used excessive heat polishing the coach skins, causing the bond to fail. If seated coach operators are having problems also the converters are not the cause of the problem.

Why isn't Prevost sharing with owners the techniques to detect bond failure? Yes this alerts the marketplace to a problem, but in today's world with the internet does Prevost really think this is a secret?

While the lack of rivets makes the exterior look great and eliminates the usual paint lifting around rivets, and eliminates the skin buckling between rivets has anybody considered the use of riveted panels as replacements for bonded panels? Unless Prevost had an accelerated test program involving thousands of heat up and cool down cycles to test the adhesive now being used I would only feel comfortable with mechanically fastening the skins to the frame. It will take a lot of drill bits to get holes into the frame (the skins can be prepunched), but once the skins are bonded and riveted you could call the repairs a permanent fix.

What happens to the insulation behind the bonded skin. I was always of the opinion that after the panels on the exterior are installed, the entire shell is subjected to a spray foam insulation application from the inside which would further bond the skin to the tubular frame. When the outer panels are removed does this rip apart the foam insulation, and if it does should the entire skin be assembled without rebonding the insulation?

What kind of record keeping is being done by Prevost QC to correlate the failure of the bond to a specific production period, to the age of the coach, to how the coach is used and stored, to where the coach is typically used? Wouldn't this pin point with some degree of accuracy which coaches may be susceptible to bonding problems and which may never have problems?

Will the repercussions of this problem affect how Prevost stands behind their customers on this and other problems. The cost to repair a single bus has to be enormous. At what point does the burden of the repairs shift from Prevost to the coach owner? I can envision where this issue takes real value from every single coach owner whether there is a bonding failure issue or not.

What happens to the buyer of a coach who is not a POG member and who does not read or participate in forums? Is that buyer totally screwed?

[JIM KELLER]

Jon, Outstanding ! And this is why this Topic needed it's own Thread.

[Kevin Erion]

When I found the 01 Marathon with bunks and looked at it to buy, I also checked each panel to verify if it had any that might be loose. I did find one that I felt would qualify as loose, I called Bill Jensen before the purchase to see what Prevost would be willing to do. He told me that I would have to take it to a Prevost center for inspection before he was willing to say anything but he did say that if a panel was loose, they would change them all. I belive the feeling with that is that why do them one at a time, it is more cost effective to just get it all done.
Prevost Mira Loma agreed that a panel was loose so we scheduled for the time needed to do them all. It is my opinion that the sika-flex glue that they originally used would get hard and brittle and the new style sika-flex stays more flexible and able to "give" with the expansion and contraction of the materials.
Is the bus as good as new, time will tell. Is Prevost going to stand behind every loose panel bus out there, time will tell, I have to wonder after 10 years from manufacture date how they will handle it, I hope the same way as now. Would I go thru the process again if I had to knowing what I know, I guess that depends on the bus conversion and if it is what you are looking for, this Marathon is what we wanted and they only made 4 of them. One of the 4 I passed on because it was so bad from the inside out that no amount of work would get it back to what I wanted, the other 2 had some different interior colors that would not work for us.
I know that there are some 05 shells that have a similar problem as the early shells, something to do with a shift change at the factory and the new crew that did the glue didn't clean the metals correctly and the bond did not stick. I guess it is also very important that both materials are cleaned with the correct solvents before the glue is applied.
I also understand that there are some Prevost factory slides that the roof of the slide needs more reinforcements so they have to remove the roof skin, add the additional bracing and reinstall the roof skin.
So all this information has to make you wonder if newer is better, in my opinion it is if the gains outweighed the down side. We had a 99 XL45 Marathon that was a great bus but I wanted the bunks for my girls and I also like the looks of the new shell with the awnings on the roof. We also enjoy the larger windows, it gives a feel that the inside is much larger. But all these nice things come with the trade off, I can only hope that now that the side skins have been replaced, they won't come loose in the future, time will tell and if they do, will they do it again? Will I want to go thru it again, I guess we will see!
These are my opinions and the information I described above is from my observations and are not quotes from Prevost, Prevost spent a lot of money to fix my bus. I am the 3rd owner and I could not ask for better customer service from the Company! I do have a different story to tell about the service center that did all the work!

[rickdesilva]

I thought I would bump up this thread again to get some more info. I ran my coach from NJ to Florida a few weeks ago and noticed a few panels had a slight "bulge" in some areas, nothing extreme. Just a very slight "bulge" about 2x12 inches in the middle of the panel on the flat section between the creases . Nothing that I would suspect that there was a problem. Nothing seems to be loose nor do I have any water leakage. They probably have always been there but I never paid attention to them. Based on the discussion here, I thought I may have the beginning of the dreaded XLII panel adhesion problem, what should I be looking for?

[Kevin Erion]

Rick,
I discovered mine by trying to lift the panel at each seam. I don't know of any way to try to check the panel in the middle area where they bond to the frame.

[Jon Wehrenberg]

When I have checked for delamination on bonded products we produced we chose a suitable tool such as a wood handled screw driver and we thunked (that's a highly technical term) across the surface lightly.

If there is a break in the bond there will be a distinct difference in the resulting sound.

Rick can lightly tap on the areas that appear to have bulged and compare the noise to surrounding areas. If the bond has broken the noise will have a "tinny" sound instead of a dull thud. Hard to explain, but very obvious.

I think in the case of the XLII where there is no tell tale rivet line the guy doing the thunking will have to discern where the structural members are and try to develop an ear to the different sounds created by a skin with the foam insulation bonded to it between structural members, the skin bonded to the structure, and the skin that has delaminated from the structure or the foam if Prevost still foam insulates the coach after the skins are applied.

I wouldn't get as concerned about delamination from the foam as much as if the skin is separating from the structure.