How to Fix Cracked Paint - Car Craft Magazine

This small crack appeared on the corner of the extreme rear edge of the quarter-panel. While you might be tempted to simply grind out and redo the filler, resist that temptation and go all the way back to bare metal to find out why the crack occurred in the first place. If you don't do it the first time, it's very likely you'll get a second chance at it.

This small crack appeared on the corner of the extreme rear edge of the quarter-panel. Whi

Whoops, there is a big crack in your paint. You didn't see it before, but there it is. Was it the Bondo that cracked or was it the application of the paint? How do you find out? We're going to show you. There are many reasons you might need to spot-repair your otherwise perfect paint job, such as a door ding, a paint bubble, or a large scratch, but we are going to show you a worst-case scenario-ours was a sheetmetal failure under the bodywork.

To get some expert advice on how to deal with this issue, we spent a day at Muscle Car Restorations in Chippewa Falls, Wisconsin. These guys are well known for their world-class full restorations, but they are also glad to take in partial work. This is doable in one day, so you shouldn't have to miss your next event.

PARTS LIST
DESCRIPTION	PN	PRICE
3M sandpaper, 80-grit	03005	$2.99*
3M 400-grit, wet or dry	03018NA	3.99*
3M 1,500-grit, wet or dry	03002NA	3.79*
3M 3-inch 36-grit Roloc disc	22393	47.00/box 50
3M green bristle disc	07526	104.90/box 10
3M Roloc disc holder	05540	18.17
3M reinforced weld grinding wheel	051131-01991	5/33.65
3M Scotch-Brite pad ultrafine gray	07448	0.25
Evercoat Rage Xtreme	120	40.25/gal
PPG Acryi-clean	DX320	231.51/gal
PPG color blender	DBC 500	56.49/gal
*Checker/Schuck/Kragen Auto Parts

We started by thoroughly cleaning the area with PPG DX320 Wax and Grease Remover and then carefully ground out the area with a 3M 3-inch 36-grit Roloc disc. Watch out that you don't allow the disc to touch another finished part of the car or a piece of chrome trim. A 3M Roloc bristle disc will help you to clean out the hard-to-reach places without removing any sheetmetal.
We started by thoroughly cleaning the area with PPG DX320 Wax and Grease Remover and then
A small screwdriver or pick was required to clean out the crevices. What was uncovered was a seam that was brazed together at the factory. Perhaps the body filler didn't stick to the brass properly or maybe the brass just wasn't holding the seam together anymore. Whatever the reason, the seam must now be welded to prevent any future issues.
A small screwdriver or pick was required to clean out the crevices. What was uncovered was
After removing the old factory brass, we started to weld up the seam. This kind of welding can be a little delicate in that you must get good penetration while avoiding overheating the surrounding metal. The trick is to slowly build up the area with small beads while quickly quenching each one with compressed air.
After removing the old factory brass, we started to weld up the seam. This kind of welding

The photo shows you the most red you ever want to see at one time. Think of it as building up the area with a series of tack welds. Never run a complete bead. If you are welding for more than about one second at a time, you are taking too long, so you might want to practice on some scrap to get your settings right before you attempt this for real. Your goal is the minimum heat that still yields good penetration. Wire in the 0.023-inch range works well.
The photo shows you the most red you ever want to see at one time. Think of it as building
After we filled in the area, we cleaned it out with a bristle disc and then used a 3M 3-inch weld grinding wheel (a worn-down one is easier to control in tight spaces) to smooth out the area so we could see where the low spots were.
After we filled in the area, we cleaned it out with a bristle disc and then used a 3M 3-in
We added whatever additional beads were necessary to fill in any holes and ground it smooth again. When you are close, a rotary grinder will make it easier to contour the surface and finish the edges. It's important that you don't leave any high spots. You want some room for body filler or you will end up using the grinder again.
We added whatever additional beads were necessary to fill in any holes and ground it smoot

Lately, we've been using Evercoat Rage Xtreme for most of our bodywork. We've found that it dries quickly and is self-leveling, so it needs less sanding. The old-school stuff usually requires heavy-grit sandpaper to finish the job. The Rage sands with 80-grit, saving time and fingerprints.
Lately, we've been using Evercoat Rage Xtreme for most of our bodywork. We've found that i
We used 80-grit to shape the filler and then finished and blended or feathered with 400-grit about 3 inches out from the edge of the filler. Then we wiped the area down with the cleaner again.
We used 80-grit to shape the filler and then finished and blended or feathered with 400-gr
When we sprayed the primer, we put the masking paper on reversed and folded it back to provide a rolled edge to help feather the primer later.
When we sprayed the primer, we put the masking paper on reversed and folded it back to pro

After the primer dried, we feathered it with 400-grit until we couldn't feel the edge with a finger and then wet-sanded it with 1,500-grit.
After the primer dried, we feathered it with 400-grit until we couldn't feel the edge with
The final step before sealer and then paint is to use a wet, fine Scotch-Brite pad. We worked the pad a few inches farther out around the repair and scrubbed the paint just enough to take the shine off the clearcoat.
The final step before sealer and then paint is to use a wet, fine Scotch-Brite pad. We wor
Of course, we cleaned the area again and then sprayed sealer over the repaired area and just a little beyond. After the sealer was dry, we used nonsilicon rubbing compound to remove excess overspray. This will reduce how far you have to feather out the color. We degreased again and were ready for the basecoat.
Of course, we cleaned the area again and then sprayed sealer over the repaired area and ju

Two coats of base color are a good idea, and you may even need three depending on how your color covers the sealer. After the base dried, we sprayed one coat of clear just far enough to cover the color.
Two coats of base color are a good idea, and you may even need three depending on how your
Here's the secret to getting a perfect blending of the new color with the old. PPG produces a color blender that we sprayed on the edges of the clear to essentially melt everything together. Then we followed that up with another coat of clear, this time applying it out a little farther. After one more application of the blender on the edges of the last coat of clear, you can put the spray gun away. Be sure you understand all of PPG's instructions when using the company's products. All that remained was to follow standard color-sanding and buffing procedures and we were good.
Here's the secret to getting a perfect blending of the new color with the old. PPG produce