Re-appearing run in clearcoat

John Milner

John Milner

Promoted Users
There is a run in the quarter panel of my car. The car has been painted for several years. Back when I tried to fix the run, I carefully used a razor blade to take most of the run down. Then I carefully sanded the run with 1,500 grit wrapped around a paint stick to get the high spots. I feel like the run is flat. I buffed the run with a wool pad and 3M compound in the yellow bottle. After doing this, the run completely disappears for a week or two. After a while, it comes back. Here are some pictures of the run. The rest of the car looks fine and I hate to tear the car back down and re-paint it but if I can't find a solution, that may be the only way. Does anyone have any suggestions?
 

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The run was not completely removed. Chances are your buffing compound has filler in it that temporarily hides the remnants of the run.
When removing a run you have to get it completely level to the surface.
P1010004.JPG


Below still isn't good enough. You can see hints of the run on the left side and it gets progressively worse towards the right side.

P1010002.JPG


Below the run is almost completely gone. Notice you can still see what looks like a shadow outline of the run.

At this point it is 1000 grit scratches so I will sand with 1500 and then 2000 before buffing.

P1010001.JPG


Once done with the buffing:
Runs Gone.JPG


Left Rear Quarter.JPG
 
Agree with '68. Looks like you had some solvent pop also in the heavy spots, which is why you are getting the discoloration. There is still holes that are full of compound or wax. 1500 is difficult to remove runs with. You need to start with 1000-1200 maximum, then work your way finer as '68 did above. Use some wax and grease remover before sanding.
 
The main thing is to make sure the quarter has had a lot of raw sun before sanding three or full days if it has not.
Sand like Tex said and at least a day before buffing. When you think you have it buffed out, wash with wax and grease remover to ensure the glaze is not hiding it.

The only other option is if you have an infrared lamp.
 
I try to eliminate about 90% of the run first, then let it cure at least another day
because the run, being thicker than the surrounding paint will always be
softer, which makes it sand differently than the rest of the paint.
I usually use the heat lamp on them
 
the solvent pop is what is killing you here. with all the pop i see there i dont think your ever going to get that white to go away permanently. by the time you sand the pop out your going to be down to base. you can certainly try what everyone suggested above but in the end i bet your going to have to spot prime that area and reshoot the fender. you could also sand the whole fender, wipe totally clean with reducer then reclearcoat it. its going to be tough to bridge the solvent pops with clear but you could lay on 3 coats, let it set up then dab clear in all the pops that didnt smooth over. let it cure out then block your dab ins, sand and buff the whole fender.
 
Agree with Jim - have had the same problem. Easier to just sand - paint and re- clear . Will take less time and chances are after you work at it you’ll sand through and need to repaint anyway
 
Thanks for the replies everyone. I will likely give it another try with some finer sandpaper and re-buff to see what it looks like. It did not occur to me that was probably solvent pop and compound filling/drying in the tiny holes. I believe in the end I will likely need to re-paint/clear the whole car.
 
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