Rust bubble

[Daddyoh]

Anybody have an idea of what it would take to fix this? Rt. rear quarterpanel. Thanks.

[LivesNearCostco]

I don't know bodywork, but isn't the answer to cut or ground out the rust, then fill, sand, prime, sand, paint and clear coat? Of course getting the paint to match exactly probably requires repainting the whole panel or blending.

[BCS_ZHP]

Quick, easy, & cheap -- remove bumper & grind away the rust, bondo the area, prime & paint blending into paint in the surrounding area. Probably a $300-500 fix as no new parts required. And if all the rust is not completely ground away, guaranteed to recur at this same spot in a year or two.

Better, harder & costs some more -- remove bumper, cut away lip to ensure any compromised metal is removed, weld in new lip, bondo weld joint outside & in, new wheelhouse undercoating, primer & paint panel while blending in a much larger section. Probably double the cost. The rust will not recur at this same spot.

Old school -- it looks like the origin of that rust is right on that crease, potentially could grind that away so there is an actual gap in the metal on that crease, then build up a new crease by welding it, regrind the crease to smooth, a little bondo for a smoother finish, prime & blend paint. Most guys don't like to do this because its more time consuming, harder to build up with metal then grind the welded crease correctly. Will probably need to find an old timer in order to get someone willing to do it this way. Remember in the old days when some guys said they did not bondo their frenched lights, rather they leaded them in, this is that process they were referring to.

[danewilson77]

Crazy that many of us here have a bubble in that same general area.

Williamsburg, VA, Droid DNA, Tapatalk

[BCS_ZHP]

There's a lip on the inside there and it ends up holding road dirt. Then you drive in the rain and get that area wet and the packed in dirt holds the moisture. A perfect storm located here -- a corner that's hard to apply the undercoating to originally, dirt & road crap hit that area to eat away the thin undercoating, now add some dirt & water, let it all hold/ferment for months & years, you're gonna get rust.

[danewilson77]

There's a lip on the inside there and it ends up holding road dirt. Then you drive in the rain and get that area wet and the packed in dirt holds the moisture. A perfect storm located here -- a corner that's hard to apply the undercoating to originally, dirt & road crap hit that area to eat away the thin undercoating, now add some dirt & water, let it all hold/ferment for months & years, you're gonna get rust.

Right... But I don't hear of/see any bubbles on the driver's side (same location)?

Williamsburg, VA, Droid DNA, Tapatalk

[BCS_ZHP]

A hypothesis -- the roads are crowned so more dirt and crap drifts/collects on the right side, same for the water and even salt in the winter. When I was into older muscle cars the ones I looked at that had rust in the quarter panels, the right side always tended to be worse than the left.

[danewilson77]

Crazy.

I'll buy that.

[CERF04ZHP]

Crazy that many of us here have a bubble in that same general area.

Williamsburg, VA, Droid DNA, Tapatalk

Same exact spot. Waiting for spring to have fixed.

via EVO.LTE

[Daddyoh]

The owner of this car that's for sale says he had an '01 M3 with the same stuff at the same spot.
I just washed mine yesterday, but I think might go see if I can clean mine at that spot now, lol.
Thank you Bruce and everybody for your input.
I'll buy the hypothesis too.
It won't be my money, so we will see.