Projects & Repairs --> Collision Repair --> Dent Repair
Repairing a long gouge in a car door. Pro Auto Body Technique:

Fixing A Long Gouge
In A Truck Door

 

In This Article:

A long narrow dent is pulled out with a stud welder and slide hammer. The metal is smoothed with careful heating-and-shrinking techniques, then filler is applied and sanded smooth.

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Skill Level: 4-5 (Advanced to Professional)

Time Taken: About 12 Hours

By Jim Wilk, Licensed Auto Body Technician

Start:

This Ford F250 got too close to a boat trailer at the marina.

There were two gouges in the side of this vehicle, indicated by the pairs of red arrows.

 

There is a gouge above and below the structure line.

(Structure lines are used in open areas of sheet metal to give strength.)

 

I'm repairing the top crease first.

 

I exposed the metal in the crease and at least 4 to 6 inches around it.

This dent was an exception because the structure line just below it, so I only removed the paint just beyond the edge of the "valley" of the structure line.

 

Then I applied the studs with the stud welder.

 

With the slide puller I pulled the metal out and hammered the high spots and ridges.

The goal here is to pull the metal outward and then hammer it back just enough to make the surface smooth. This pull-and-hammer technique is used for each stud as I progress along the crease.

 

With nippers I squeezed the head of the stud and twisted to cut it off.

 

Next I moved to the gouge below the structure line.

By pulling out the top dent first, there was no longer any "tension" holding the door inward.

WHY? The crease at the top helps prevent the sheet metal from "oil-canning". BUT... in this case we want the sheet metal to "oil-can" and pop outward. So I removed the top crease first and then used the suction-cup puller to force the metal to pop out.

With a pneumatic suction cup I pulled most of damage outward. 

 

This pneumatic suction cup can pull with a force of up to 90 pounds.

 

I purchased this tool over 35 years ago and the company went out business 30 years ago. Many technicians and tool men have tried to find this tool and can't.

 

After baring the metal I placed the studs, following the crease all the way down.

I spaced the studs about three-quarters of an inch apart.

 

Then after a coffee break, I started the tedious process of pulling every one of those studs and working the metal with a hammer.

This procedure took at least an hour to an hour and a half.

 

Pro Technique:

Once the steel door skin has been dented, the metal becomes stretched. Through many years of body work experience I have learned how to heat and shrink stretched metal. This technique was taught when I first started my apprenticeship in 1969, but today this technique is rarely taught.

  • With a grinder, I skimmed the area, applying light pressure. This heated up the metal.
  • Next, I lightly hammered the high spots and ridges.
  • Then I wiped the area with a cold wet rag (red arrow).

The heat of the grinder will expand the metal and the cold water will shrink the metal.

 

After doing this procedure about five times I finally had the crease out of the metal.

Other situations may require more or less than five heating/cooling cycles.

This heating and shrinking process will also add strength to metal.

 

It is a judgment call to know when the metal is ready for this next step:

To smooth out the irregularities in the metal, I applied a light layer of plastic filler.

 

Before it totally hardened I used a grater to level the surface.

With this procedure I have less sanding and dust.

 

I call this a grater, but it's also called a Surform tool.

I have found the blades at Home Depot.

 

The main part of this tool is over 30 years old. This style of handle may be hard to find, but similar tools are available.

 

When the plastic was completely hardened I started sanding.

First I used the pneumatic sander with coarse 40 grit sandpaper.

After sanding with 40 grit, I applied a coat of automotive putty filler. I used a plastic spreader to apply a smooth coat.

Then I hand sanded it with a long board sander, first with 80 grit and then I with 180 grit.

 

Now the repaired area was ready for priming and painting, which was done by another professional.

 

After the painting was done, the painter polished and waxed the repair area.

 

After washing, the truck was good as new.

 

More Info:

Tools Used:

  • Stud Welder
  • Slide Hammer
  • Suction Cup Dent Puller
  • 7" Disc Grinder (24 or 36 Grit Disc)
  • Pneumatic Sanders
  • Grater (Surform Tool)
  • Long Board Hand Sander
  • Body Shop Hammers

Materials Used:

  • Studs
  • Plastic Body Filler
  • Sandpaper: 40, 80, 180 Grit

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Written December 6, 2007