There's a bondo crack in the drivers rear quarter of my car. It's Benny there ever since I bought the car and I don't know the history about it. Should I replace the rear quarter or just get it fixed? It's 3/4s of a foot long exactly above the wheel well

 

Do you have any pictures?

 

I dont have pics but can take them tomorrow

 

You are going to need to remove the old bondo before you can tell if you can rebondo it or if the metal needs replaced. Bondo isn't intended for anything 1/8th of an inch or deeper.

 

Body filler is intended to smooth a surface not fill a canyon, the problem is people tend to use it in the wrong manner. Take a fridge magnet and see if it will stick to the area where the crack is; this will give you an idea if there is any metal or is the filler so thick it wont stick. Either way all the filler wil need to come out, what scares me in that area is people tend to try and use filler to fix rust, I have seen people use Monopoly hotels to form the point on the wheel well edge, then use glass and bondo to shape it all.

 

Well, like someone else already said, you are going to have to dig the old bondo out and see what lies beneath. The crack can be there for any number of reasons: the surface may not have been clean enough before body filler was applied, or--since body filler does not flex quite as well as the metal under it--the quarter may have moved around enough to cause it to crack, or the body filler is simply too thick. The obvious problem is of course, once you grind into the bondo, you will have to repaint the quarter panel. Since there is no body line between the quarters and roof panel on our cars, that means you will have to blend the paint into the roof and the other quarter. By the time you've done all that, it may be worth replacing the quarter panel, so you won't have any bondo at all (that is, unless you use it to fill the seam where the quarter is spot-welded to the roof panel)
On the other hand, replacing a quarter panel is a very involved enterprise. It requires drilling out spotwelds, re-welding, leading, fitting, etc. And speaking of fitting, the reproduction panels never seem to fit as well as what came from the factory, so gaps between doors and quarter, or hatch and quarter will be probably be off. So, it's sort of a pick-your-own-poison situation.
Grind the bondo off and see what you got. Maybe the metal is in decent enough shape to be fixed without removing the entire quarter.