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Rust advice needed.

I see from some of the postings that some of you Longchamp owners have had the car really apart and done a thorough job of fixing the rust. I plan to do the same but hopefully on a smaller scale. The good news is that the rust on my car is very concentrated. There’s no rust in the bottom, doors, front fenders etc. But there’s rust (on both sides) in the following areas:
1. Rocker panels
2. Behind rear side window, just where the window opener attaches on the inside
3. Rear fender, 1” above the wheel well flanges (non GTS car)

On 1. I’m not surprised, the material is about half the thickness of my 68 Camaro rocker panels. What were they thinking, it’s not that they tried to make a lightweight? Wink
On 2. The rust is serious in a specific area where there on the inside was some sponge (sound deadening?) material. The metal that the 3 screws that hold the window opener screwed into is mostly rusted away.
On 3. Usually you see water and maybe salt from the wheel wells starting to rust the flanges, but on mine it starts further up and the flanges are is mostly intact. So rust comes from above and inside, not beneath from the wheels.

And now to my questions. On 2 and 3, are your cars the same? It seems to me that water coming from above could cause both? And the big question is: where does it come in? The only possible areas it could enter are top of front window, side window or rear window. I see no sign of rust or anything around the windows.

If you had your Longchamp more dismantled than me, can you help? Pictures are welcome. Thanks

Lastly, does anyone know what high-volume car that has rear wheel well flanges similar to the Longchamp, I would rather buy a part and weld it in than building it myself.
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Hi Mikael,
on 3, it sounds like you may have water coming from inside the trunk? mine had a lot of problem there, because the wide flat trunk lid did not fit the seals very well, so water leaked in from above. consequently the spare wheel well, and the lower panels beside it were badly rusted. then the moisture wicked its way up the felt that protected the outer guards from the fuel tanks. Finally the alloy fuel tanks had an electrolytic reaction through the wet felt, so it ended up wet with petrol and there was a constant petrol smell from the leaking tanks. I repaired tanks with epoxy many years ago and this has not been a problem since. Main issue was to get the trunk lid seals to work well and I had to reshape the lid a little to do this. Also the closed panel between the rear window glass and the trunk lid (3" wide boxed section) had rusted out from moisture in the window seal and condensation from the water in the trunk. Everything repaired was thoroughly sprayed inside with fish oil. Bad smell but great product.
good luck.
Hi Peter
Thanks for the idea

There's no water in my trunk, even though it's a daily driver and not even after a machine car wash. On the other hand, the rubber around the trunk looks new and my guess would be a different size than original because the trunk lid is hard to close, so maybe it leaked earlier. But I found no rust in spare wheel well, and no problems with the tanks.

Talking about rust and the tanks, I got worried first time I wanted to fill it up, because both tank screw-on lids were extremely rusted on the inside, but the throat looks OK and I have no problems with dirt getting in the carb or plugging fuel pumps.

I see you also have the Pantera/Longchamp combination, perfect Cool
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