Automotive Collision And Bodyshop Repairs – Everything You Need To Know!

I had an unfortunate parking lot accident recently.

Hey, it happens.

Someone backed into my pride and joy. It crumpled and tore the plastic bumper cap on my car’s rear. Ouch!

Thankfully the $4,200 repair turned out perfect.

Yet, the incident left me asking questions about the use of plastics. In particular, modern cars use plastic bumper systems and fascias.

They are made of Thermoplastic Olefins (TPOs), polycarbonates, polyesters, polypropylene, polyurethanes, polyamides, or blends of these compounds.

Often times, glass fibers are added which provides more strength and structural rigidity.

Most engineers absolutely love these materials because it affords much more freedom in styling, building and placing components.

The Problem With Plastics

But, despite the benefits, plastic body parts have limitations and drawbacks.

For one, painted plastic body parts are easily stained and dulled.

To understand why, I researched the process of painting plastic bumpers. Turns out it greatly differs from painting metal body panels!

Flex Agents

Bad Bumper Crunch
It doesn’t look like much, but the complete rear bumper cap had to be replaced and repainted. Repair costs can be hefty. In my case, it was $4,200. Ouch!

I’ve long known it is necessary to add a “flex agent” to paint that will be applied to plastics.

This allows the paint to move with the plastic part without cracking or delaminating.

Paint flex agents also cause the cured paint to be more porous.

In essence, there are microscopic pockets which allow paint to remain spongy and (of course) flexible.

Most of the pockets are deep in the layers of paint, but some float to the surface.

There’s something else…

Another effect of flex agents is the paint will remain soft.

So what’s the big deal?

Paint on TPO parts does resist chips well, but it will dent (small pock marks) from road stones.

To be clear, porosity and softness afforded by the flex agents create challenges.

First, the paint doesn’t resist stains as well as paint without a flex agent.

Second, the flex agent paint cannot be buffed or polished with anything more than the finest polish, or the finish will be ruined.

Here is something people don’t realize:

Buffing does not increase gloss on this type of paint. On the contrary, it smears it.

All too often car owners use a rubbing compound on soft plastic bumper caps to remove, for example, bug stains.

Guess what?

The paint dulls and never returns to full gloss.

So sad, yet so true.

I have also noticed etching from hard water and bird droppings is worse on painted plastic parts.

Auto Body Shop Tango

No one likes the thought of taking their car to the body and paint shop.

Horror stories abound!

Endless stories about swirl marks, paint that didn’t match after 3 months, over-spray on the rest of the car, and so on.

It is unfortunate that for every good paint and body shop, there are 3 mediocre shops and 2 bad ones.

Guys, be prepared when you take your shining beauty to the painter.

Know what to expect before you get there. Know what questions to ask to qualify the shop and the painter.

Unfortunately, paint and bodywork is difficult to scrutinize on the spot. You may not know there’s a problem until days, weeks or months later.

Educate yourself!

Good Car Painter, Good as Gold

There are several stages to paint and body work.

And minor fender-benders aren’t always simple. For example, some parts removal and replacement can be needed.

Common replacement parts include lights, bumper caps, hoods, spoilers, trunk lids, quarter panels and doors.

Virtually every component of your car’s body can be replaced. Manufacturers do make the replacement parts.

For serious accidents, it is often necessary to repair the internal, structural system.

We’re talking the chassis and frame.

For these repairs, seek the counsel of your insurance company. They should be intimately involved in major repair work.

Let’s now talk preparation.

Preparation has many facets. Think of it as perfecting and protecting the bodywork for painting.

Technicians prepare by cleaning, straightening and aligning panels to be painted.

Different shops have different methods for perfecting small dents, dings and ripples.

Here’s the deal:

Body shop technicians use fillers, but the quality and application methods vary.

Be sure to ask questions early on because, once the bodywork is complete, the car body technician prepares the body panels to accept paint.

This part involves the use of sanding papers and paint primers.

Body shop technicians are also responsible for masking, leaving only the parts to be painted exposed.

We can’t forget about the painting process.

In most shops (small shops are different), the painter doesn’t do bodywork. Likewise, bodywork technicians do not paint.

It is really the painter who determines if a car is ready to be painted.

A good painter will closely scrutinize the preparation work.


Because bad prep will make him or her look awful at their job! In fact, the smallest details can make a paint job look sub-par at best.

Let me give you an example:

If a grinding disk is used, and the circular grinding marks aren’t fully removed, they will show up in the final paint.

Likewise, pinholes in filler are a common prep problem.

So, the painter should find any problems and reject the car if it’s not 100% ready.

Finally, we have buffing and blending.

It is my personal belief that a good painter rarely needs to buff his paintwork.

If a car requires buffing, because the paint is oxidized or slightly faded, it should be done prior to painting.

Why you ask?

This helps to correctly match the repair color and finish.

Auto Body Shop Horror Stories

My horror story takes place in California where I had left my BMW M3 in Sacramento for local transportation.

Even though my daily drive to work was short, the Sacramento roads have a lot of debris. The front of the car had heavy road stone damage.

At the end of the project, I decided I would have the M3’s paint repaired prior to transporting the car down to Los Angeles.

Not being a resident, I didn’t know a painter. I consulted the local dealer.

As it happens, the same family owns the Porsche dealership in Sacramento, and I had seen their paintwork.

It was perfect in every way!

So, I assumed I’d get the same quality of work from the BMW facility. What I did not realize is that they send their paintwork out to local shops.

Mistake number one on my part!

Timing being what it was, my M3 wasn’t ready until the day I was packed up and heading out of town.

Just my luck, the paint shop delayed the work by 3 days.

When I got the car back, it was filthy.

Yet on first inspection, the paintwork looked pretty good. That is, until I loaded the car on the transport trailer.

On closer inspection, the paintwork was horrible.

Three problems stood out.

First, the repair facility was lazy. They didn’t mask off or remove the plastic brake cooling ducts. The ducts, previously black, were now silver.

Second, the lower cooling intake vent was matte black from the factory, but the painter sprayed it silver instead of masking it off or repainting it black.

Worse, however, someone used a sanding disk and left deep grinding marks on the front spoiler.

Strike three! They used a buffer on the paint and stained all of the black rubber and plastic parts with silver paint from the buffing wheel.

Needless to say, I was furious, and they knew it.

But what could I do? I was headed out of town.

The repair bill was $1,400. They wanted a personal check or cash.

Sorry, guys, here’s my credit card. (Never pay for a repair by cash or check.)

On my way out of town, I called my credit card company to dispute the bill.

There were hours of negotiating. Eventually, the owner agreed to reduce the bill by $800.

Do-It-Yourself Paint Repair Aspects

On this website, I won’t be talking about doing your own repairs beyond PDR.

Many of you like to be involved in the repair work. Indeed, for the best results, you must be involved in some way.

In fact, you can do a lot of prep work yourself. The stuff that will help make the repair work better.

For example, cleaning the car and removing trim is an important step.

Most body shops hate doing it.

In almost all cases, you will get a better repair by removing the trim from panels to be repaired and painted.

Most body shops simply mask around trim (lights, side markers, door handles, chrome, bumpers). It takes too much time to remove it.

Of course, there is some risk in removing and reinstalling trim.

But the problem with masking trim is that there is always a masking line. This leaves a clear sign that the car was painted.

It’s really a judgement call.

I think the end result is often better if you take the time to remove small trim parts.

There’s something else you should know…

It is important to clean your car completely before taking it in for repair.

Remove waxes, sealants, polishes and silicones from the repair area.

You see, the body shop technicians will use Prepsol (a paint preparation cleaning solvent) to wipe down areas to be painted.

How well do you think they will clean?

If you have wax in the deep crevices between a door and fender, do you think they will take the time to scrub it out with a toothbrush?

Don’t kid yourself!

Do the deep cleaning. Make sure everything is cleaned, even down to the lowest part of the body.

Getting A Feel For Hired Help

You’ll want to meet two people when you take your car in to a shop for a repair.

The manager and the painter.

Let the manager know what you’ve done to prepare the car. While he may tell you it wasn’t necessary, you know better.

Heck, he may even warn you about problems with reinstalling the trim.

Perhaps he doesn’t appreciate the work you’ve done and does not understand car enthusiasts.

If so, turn around and walk out. You’re not in the right place.

On the other hand, he may appreciate such preparation!

You must find out. This is actually a key indication of future events.

In any case, let him know you want to inspect the car prior to painting.

This immediately tells him that you know your stuff.

The result?

He’ll know the car needs to be properly prepared before he calls you.

Your Pal, the Professional Painter

Ask to meet the painter and spend a little time getting to know that person.

Let them know you are a fanatic about your car. Make it clear that careful masking is important to you.

Be very specific.

Mention the wheel wells, underbody, engine compartment, air ducts and other inlets.

Indicate that you want no apparent signs of paintwork when the job is complete.

You’ve found the right place if the painter understands. If not, turn around and head for the exit.

The Pre-Paint Inspection

Do not wait when the manager calls you for a paint pre-inspection.

Go immediately and inspect the work.

If they replaced a body panel, look at the alignment. Is it straight with an even panel gap all the way around?

Did they do a neat job of applying body panel cement at the mounting points? If they repaired a dented panel, can you see the repair?

Thump the repaired area.

Does it sound “thick” like they applied a lot of body filler instead of pounding out the dent?

Have all of the pinholes and grinding marks been filled?

Be very critical.

Folks, it doesn’t get better when the top coat paint is applied!

Post-Paint Inspection Period

It’s time for you to pick up your car.

Inspect the work again and again.

Did they buff the paint? Look closely to be sure they didn’t leave swirl marks.

Look for overspray.

Look for a consistent paint finish that’s free of orange peel, fish eyes and other obvious painting defects.

Pay by credit card only when you are satisfied.

Review any problems with the manager if you aren’t. Give them a chance to fix their work if the problems can be corrected.

When Paint And Bodywork is Complete

The paint will be cured by the time you get your car home – at least enough to begin reinstalling trim.

Be careful, though! The paint is still soft and can be marred.

If you are reinstalling a large part, such as a bumper, do not work alone.

Ask someone to help you!

Do not use any chemicals for 30 days after paintwork. Simply wash with cool water and a good wash tool.

Warning: This restriction applies to wax too.

Wax too soon and you will risk discoloring the paint from trapped solvents. They need to off-gas completely.

Be sure to visit our paint repair section!