Removing a dent using a dent puller – Auto body work 101

by David Lavalley on February 19, 2013

It happens to us when when we least expect it. A few months ago my wife was talking on her cell phone while driving. Next thing I know, she comes home with a nasty dent on her driver side door.

At first I considered replacing the whole door but this would cost several hundred dollars to do. Finally I decided that it was time to break out the old dent puller and get to work.

Dent is car doorMany people think that performing body work is a difficult task and is best left up to the professionals. This theory is supported when one sees that car with 3/4″ of Bondo slapped on the side. While it does require some skill to do, the average do it yourselfer can easily accomplish this task. The key to doing great body work is to take your time and carefully examine your approach before taking action.

How to do body work on your car

There are a few basic tools and products that you will need in order to get started. Harbor Freight is a great place to find most of the items that you need. Print this list out and take it shopping with you.

Items that you will need

  1. Dent puller. I used one similar to this one from Advance Auto Parts. Harbor Freight sells one that is a little heavier duty for $70 if you would like to spend the money. There are of course other options such as the weld on studs that do not require drilling but these can get expensive.
  2. Angle grinder. I picked up an angle grinder from Harbor Freight on sale for $12 and it works surprisingly well! You will also need a grinding disk  to go with it. They are the thicker disks, not the thinner ones used for cutting.
  3. Power drill and small drill bit. Most DYI people already have a power drill and drill bit set. The drill that I prefer is the Craftsman C3 cordless drill.
  4. Assorted stand paper. 80 grit is a must when it comes to sanding excess bondo. Also pick up some 200, 400,800 and steel wool.
  5. Rubber sanding block. These are really cheap and readily available.
  6. Bondo and Bondo cards. This is a must when it comes to getting that smooth surface.
  7. Red putty filler. Used to fill in any pin holes or small imperfections prior to priming.
  8. Primer. While most primers will work, I tend to reach for the mid range primers. $.99 primers are usually thin and spit when sprayed. Advance Auto sells a nice primer-filler with adjustable nozzle made by Duplicolor. While a bit pricey, this is a nice product to work with.

Shopping around will allow you to pick up all of these items for less than $100.

How to used a dent puller

Drilled holes for dent pullerDepending on how bad the dent is, you may or may not be able to use a dent puller. In some cases it is necessary or more time effecient to simply replace the entire panel. This is especially true if you have a badly dented door, hood, or fender. These items can usually be replaced by removing a few bolts and replaced with an aftermarket product that is ready to paint. In my case, a door would have been quite expensive so pulling the dent was the best option.

Keep in mind that not all dents need to be pulled with a conventional dent puller. Often times, a uniformly round dent can be pulled out with a suction cup puller or even a household plunger. It is always better to try this method first because it is least expensive and does not require painting. There are various products on the market that make this task a DYI project.

If you have decided to proceed with a slide hammer puller, you will want to drill several holes that are smaller than the screws that come with your puller. You will want to pull the dent out from several points so that matches the original contour of the car as closely as possible.

To use the dent puller, start from the outer edge of the dent and work your way to the middle. Use a screw driver to insert the screw into the pre-drilled holes. Grab a hold of the handle and apply moderate pressure away from the body panel. Use the slide to “pull” the dent out. Pull just a little from each hole until the dent has been pulled out. It helps to step back and take a look at the panel from various angles. When finished, your panel should be in the general shape it once was but will have several volcano shaped bumps where you pulled from. This is okay. The next step will help help to eliminate them.

Use angle grinder to remove protrusions

Grind down dent puller holesWith the dent pulled out, plug up your angle grinder and lightly hit each hole that you made. This will help to remove the “bumps” that you made by using the dent puller. Generally, just a light grinding for a few seconds will do the trick. If you do not have an angle grinder, a Dremmel should do the trick.

Grinding down the pull marks is an important step when it comes to reshaping the panel. If this is not done, you will likely see several areas where the dent was pulled out. Once completed, The surface should be much smoother but will still have some high and low spots. These spots should vary only a little (less than 1/8″). The surface differences will filled with a plastic filler and sanded smooth.

Use a plastic filler

Mix bondo fillerUsing a plastic filler is perhaps the most difficult part when it comes to doing body work. The only reason why this part is difficult is because once the hardener is added, you only have a couple minutes to work it before it hardens. It will quickly become too hard to spread and you will have a lot of sanding to do.

Sand the working area with 80 grit sand paper to remove the clear coat. Ensure that you hit all of the low spots so that the filler adheres.

Using a piece of cardboard or similar material, remove a golf ball size piece of the putty. A wooden popsicle stick or paint stick works well. Squeeze an inch long line of hardener and mix well with the Bondo. This stuff will set up fast so get ready to spread it on the body panel.

First application of body fillerOnce mixed to a consistent color, spread the filler all around the work area while attempting to create a feathered edge on the ends. If this is your first time using bondo don’t worry if you don’t get this right. After sanding for a while you will quickly learn an application technique. Depending on how much hardener you added, you will need to wait 30 mins to an hour before proceeding to the next step.

Sand and shape filler

This is the part where most people go wrong. It only takes a few seconds to apply 1/2″ too much bondo but properly removing it will take several minutes. The idea here is to feather out the edges of the filler when it meets the metal. In addition, you will want to hit all of the high spots inside the repaired area. Try not to sand too much of the filler away and if you find a low spot, leave it. This area will be filled in using the next application of filler.

Sand the area using 80 grit sand paper until you get a nice rough shape that is similar to the original contour. The first application is not going to be perfect so fear not.

Repeat filling & sanding

Sanded Bondo With your first coat sanded and the dust blown off, apply a second coat as instructed above. Right now is a good time to use a large Bondo card to fill in the low spots uniformly. Use your finger tips as a guide to find high and low spots.

Using your sense of touch is the key to great results. Remember, if you can feel it, you will be able to see it – no doubt about it. When you think you are getting close close your eyes and feel the surface for waves, bumps, pits, inconsistencies, etc. At this point you should be getting very close to achieving the original shape.

Use glazing putty

Glazing putyGlazing putty is one of the last things that you should do when performing body work. It is a fine red putty that is applied on top of your finished bondo work. The purpose of this product is to fill in minor imperfections, creating a nice smooth surface that is ready for primer. For less then $8 a tube, this step is crucial if you to achieve a professional finish.

 

 

sanding before primingSimply apply by squeezing the tube and working over the entire area with a bondo spreading card. Spread an extremely thin layer over your work area and allow to dry. They trying time on this product is much longer because its not used with an activator. Dry time can be anywhere from 30 mins in hot, dry conditions to over an hour in cooler humid conditions. Allow to dry and stand with 400 grit or finer sandpaper to a smooth finish.

Priming

primed doorNow that the hard part is done, its time to prime. Primer provides a solid surface for paint to stick to and it can also cover any remaining perfections. In addition, it can be a great way to protect your metal from rust until you get around to painting it.

When doing body work, you should anticipate putting the top coat on within a few weeks, not months. Driving around with primer on your car for a long period of time not only looks silly but will eventually introduce water to the bare metal surface.

To prime, use a quality masking tape to mask off areas where you do not want paint to adhere. It is much easier to tape it off than to remove over spray afterwards. Don’t forget to also tape off all glass if nearby.

Shake the can vigriously and apply paint in a sweeping motion. Apply several coats, allowing several minutes to dry between coats. It may be a good idea to hit the area with steel wool in between coats and then remove the sanding dust that it leaves.

primed door side viewWhen finished, carefully remove the masking tape.

Paint as soon as possible. The painting process takes a little bit if effort but you can also do this. Stay tuned for an article on painting using a 2 stage base coat – clear coat finish.

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