fiver body sagging in the back

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WaltherDawg

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May 12, 2019
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Hello all, I am new here and have learning a lot just by ready through all these posts.
I very recently bought a 2007 Thor Jazz 2550rl. It is in pretty good shape with a few minor repairs needed. However this one I have no idea how to fix. The body is sagging in the rear, the back cover seems to be about 1/2-1" too low and is buckling over the frame extensions. I can see the I beam frame and it looks straight. My guess is the body mounts are collapsed or sagging or something.
Any ideas what it could be? How do I fix it? I do have a lot of auto maintenance experience but nothing in RV specific areas.
 
When you say "back cover" do you mean roof? And when you say "frame extensions" do you mean walls?
 
I You can see in this picture how the rear wall is buckling upward. It is more prevalent on the left side.
 

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That area is usually called the "rear cap", though technically "cap" refers to a pre-formed single fiberglass piece while the one in the photo is a simple flat wall, much like sidewall construction.

It looks as though the bumper mount is bending in the frame extension on that side. I can't see what is bolted onto the bumper there with that shackle-thing, but something may be stressing it there and causing the buckling.  Os that the area you also say is too low? Has it actually dropped (a gap at the top?) or just folding over as it buckled?

If no damage can be seen from underneath, I see little choice but to remove the skin from the rear wall and look inside. One possibility is water damage interior to the rear wall, allowing the skin to simply fold in.
 
Would need many more pictures to make an educated guess.

I'm still not clear on your terminology of "cover". Do you mean the outer fiberglass on the exterior wall? RVs don't have "body mounts" in the sense you are thinking, essentially a box is built on a frame. If that whole wall is sagging in that corner, it could be a water intrusion issue where the wall has come unbonded and lost its strength, perhaps detaching from corner metal framing. Wild guess at this point.

You need a hard look inside and out at that area, and some sort of confirmation as to whether the wall is sagging or the frame was driven upward into the wall (then later straightened).
 
I can see the frame rail. Looking down the length of it I do not see any bending. I haven't seen any water damage from inside the trailer.
I saw some brackets welded from the frame that extend to the side of the body. I assumed these are body mounts.
I guess the next step is stripping walls off? Would interior or exterior be the easiest?
 
This is from underneath. It shows the bumper extension, the bumper and where the rear wall/cap is pressing against it.
The item bolted on the the bumper is simply a receiver hitch thing to hold a bicycle rack.
 

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The main trailer frame (two parallel beams) has a metal floor grid welded or bolted across it and then the floor and walls are built upward on that.

It's not unusual for a receiver or stabilizer jack bolted to a bumper like that to twist the bumper, forcing the bumper attachment points upward or downward and buckling things. The rearward frame extension of most trailers and motorhomes aren't very robust.  If you've ruled that out, then the damage is likely to be internal, which usually means water intrusion and totted structure. Is this trailer wood-framed or metal?
 
Don't overlook a simple possibility that the bumper was just pushed in and up enough to press into the fiberglass.  There is usually some amount of flexibility to the bumper and the frame that would allow it to contact the fiberglass and then the bumper move back in place w/o easy to see damage or stress. 

By putting a jack under the bumper and extending the jack you should be able to see that the bumper will flex pretty easily.  I don't mean that you should put a lot of stress on the bumper with the jack, just enough to see that it flexes pretty easy. 

The cause of the bumper flexing could be just a simple matter that someone backing the trailer ran the bumper into some dirt or grass, pushing it up and in to the fiberglass. 
 
The cause of the bumper flexing could be just a simple matter that someone backing the trailer ran the bumper into some dirt or grass, pushing it up and in to the fiberglass. 
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Or too much weight on the receiver, especially when hitting bumpy roads for too long...
 
After reading all replies and looking a bit closer I think my next step is to pull the skin off and look underneath. This ought to be fun.
Thank you everyone for the help.
 
In your 1st picture, I see a plate on top of the bumper with 4 bolts going down thru it. I assume there is a bottom plate also. Is that assembly for a dolly wheel? If it is, that's probably your issue. You may have back into a steep driveway or entered a dip in a road, forcing the bumper up enough to hit the end cap of the RV. Just a guess right now as to what that plate is for.  Can you shed some light as to what it's for. It may help us.
I think I can see the frame between the bumper and the end cap and it's right under the major dent.
 
Before doing anything drastic, park the camper on as flat an area as you can find. 
Measure ground up to each end of the bumper. 
Measure from frame to the ground on each side, near the back.
Measure from the bottom of the camper body to the ground, a foot forward of the back.
Repeat three feet from the rear cap.

This should show what is getting bent, and hopefully, what is doing the bending.
 
Are you sure the rear panel isn?t just sliding down?  There isn?t much holding those on. What does the top edge of the panel look like?
 
All good ideas here. Next time I get it on flat level ground I will have plenty of measuring to do. Will also check out the roof and pull the plastic sheets away underneath to see if that gives me any clues.
 
WaltherDawg said:
All good ideas here. Next time I get it on flat level ground I will have plenty of measuring to do. Will also check out the roof and pull the plastic sheets away underneath to see if that gives me any clues.
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Please let us know what you end up finding.
 
WaltherDawg said:
All good ideas here. Next time I get it on flat level ground I will have plenty of measuring to do. Will also check out the roof and pull the plastic sheets away underneath to see if that gives me any clues.
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Is there something you can see that makes you sure it wasn't just the bumper pushed into the fiberglass.  I think 3 people suggested that as a simple cause of the damage.
 
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