Where to Look for Rust on Your Next Used Car (2024)

Published: December 27th, 2018

Where to Look for Rust on Your Next Used Car (1)

Rust. It’s the four-letter word that has sunk more secondhand car transactions (and broken more post-purchase inspection hearts) than any other.

It’s the cancer that eats away at the very skeleton of almost every vehicle on the road, especially in the northern regions of the continent where road salt and ferocious winters lend a helping hand to the forces of corrosion.

Left unattended, rust can eventually render even the most mechanically-sound car a total loss, as it destroys structural integrity, converts suspension components to dust, and patiently puts holes in sheetmetal of all kinds.

How can you avoid falling into the rust trap when purchasing your next used car? We’ve put together this guide to tell you where to look when inspecting for corrosion, what to be worried about if you find it, and when to walk away from a sale.

Water, Water, Everywhere

Where to Look for Rust on Your Next Used Car (2)

Photo Credit: Alfred Koal/Shutterstock

For the most part, when inspecting for rust – especially hidden rust – you’re going to want to check out areas where water accumulates. This is going to vary from one vehicle design to another, but there are some common spots where water seeps in and stays long enough to start causing issues.

ALSO SEE: Buyer’s Guide: The Best Rust Inhibitors You Can Buy

If the vehicle you are looking at has a sunroof, you’ll want to check that the drains aren’t clogged. If they are, then water can sit at the bottom of the drain and start the corrosive process. Usually, the drain will empty out at the bottom of the quarter panel, or onto the rear window deck, which can lead to trunk and quarter/lower panel rust. Some cars also have similar clogging issues for drains associated with convertible tops (near quarter windows/trunk, typically draining out of the bottom of the quarter), and inside the passenger doors (look for a drain plug to pull if you can hear water sloshing around, examine the lower portion of the doors inside and out for rust).

Depending on how they are formed, the fenders themselves might retain moisture as dirt and crud accumulate and remain wet and pressed against the metal. Any curved underpanel – even those seemingly protected by a rubber or plastic covering – can fall victim to this type of corrosion, especially since a cover can actually end up trapping water and gunk. Inspect the fender lips at the top and bottom, the corners of each fenders, and the area where the bumper connects to the fender.

Salty

Where to Look for Rust on Your Next Used Car (3)

The underside of the car is most vulnerable to the effects of salt, because it’s constantly being blasted with it during winter driving. To fully inspect a car for undercarriage rust, you’ll need to see it up on a lift. Common trouble spots include frame rails (where salt can penetrate and sit, much like water), the floor panels (which can be thinner than most of the other steel under the vehicle) suspension components (mounts for swaybars, shock absorbers, and springs, especially shock towers), and the exhaust system (usually the lowest point on a vehicle).

ALSO SEE: Top 10 Best Paint Scratch Removers

The lower portion of the body deserves a good inspection, too, because any area where paint might have been removed by a rock chip or a scrape with a speed bump exposes metal to the risks of corrosion. On pickup trucks, take a look at the rear cab corners, which often take a beating from salt and moisture, as well as the insides of the cargo box fenders.

Pro tip: the driver’s side of a vehicle is often most susceptible to salt-related rust, because it gets sprayed by passing vehicles and is facing the strongest accumulation of salt on a road (the center line). Give the left-hand side of the car or truck you are inspecting additional scrutiny.

Not All Corrosion Is Forgivable

Where to Look for Rust on Your Next Used Car (4)

If you find rust, don’t panic – it’s not always the end of the world. Surface corrosion, which refers to a thin layer of oxidation found over a rock chip, scratch, or frame rails, is not something you need to worry about and is typically a cosmetic issue.

What you’re looking for is rust that has perforated metal (pinprick holes count, too), or which is bubbling underneath paint that indicates there is more serious corrosion lingering just out of sight. Bubbles are often seen on wheel wells, around the windshield (indicating a poor seal between glass and auto body that has allowed moisture to penetrate), and at the bottoms of doors. These can indicate lingering issues that will need to be addressed, so at this point, it’s up to you to decide whether this is a bargaining chip or more of a hassle than you want to deal with.

Of course, there are some types of corrosion that you simply can’t ignore. Specifically, if you discover any serious rust that indicates the need for extensive bodywork, or which renders the vehicle unsafe to drive, that means it’s time to say goodbye and move on to another option. Any holes in shock towers – at the top or along the sides – are terminal. If you see dangling suspension components because their respective links or mounting points have corroded away, that’s not something you should consider repairing. If an entire door needs to be replaced because you can see through the bottom, then you need to ask yourself how well the vehicle was actually maintained over time. Finally, structural holes – in frame rails, in subframes – are another deal breaker.

If you don’t feel comfortable with this type of in-depth rust inspection, remember: you can always take any used car to a trusted mechanic for a pre-purchase once-over the will help dispel or confirm any lingering doubts you might have. A little time and money spent up front before signing on the dotted line can save you big on repairs down the road.

Where to Look for Rust on Your Next Used Car (2024)

FAQs

Where to Look for Rust on Your Next Used Car? ›

Rust is a cause for concern, so check the body for blistered paint or visible rust. Check the wheel wells, panels beneath the doors, and door bottoms. Open and close each door, the hood, and the trunk.

How to check for rust when buying a used car? ›

Once you have the car back on the ground, pull up the trunk carpeting and check for any signs of rust. Also, check the doors, both inside and out, along with areas around the windshield and rear glass. And another rust tip: If you see any sort of exterior paint bubbling, it's likely an early sign of rust.

Where should you look for rust on a car? ›

Checking for Rust

First check underneath the car. Examine the frame rails, wheel wells, exhaust system and suspension for rusting. Look under the trunk carpeting and the doors, inside and out. Check along the front and rear windows, assessing the border around the glass.

Where to look for rust when buying a used truck? ›

First, inspect the body of the truck for sale. Do you notice any signs of rust? While some rusting is a mere cosmetic problem, look out for rust near the exhaust pipes, muffler, wheels, frame rails, and floor plans. Evidence of rust in these locations can be a sign of a more serious issue.

How do you find hidden rust? ›

Eddy current NDE is a prime method for detecting hidden corrosion in electrically conducting materials. The method is based on generating a localized alternating current field in the sample using a probe coil. The same probe coil or another detector then measures the material's response to the induced eddy currents.

How much rust is okay on a used car? ›

If the rust is only skin deep, that's a used vehicle you can keep. But if it affects the frame, that can be a recipe for pain. Check the vehicle history, and have a mechanic check out the areas you can't.

Where do cars rust the most? ›

Become familiar with areas of your car that are particularly prone to rust like:
  • Brake pads.
  • Battery terminals.
  • Body panels.
  • Wheel wells.
  • Any other areas that frequently face water and road salt.
Sep 13, 2023

Is it worth fixing rust on a car? ›

It might be worth it for you to fix the rust on your car if the vehicle is under 5-10 years old and has low mileage. Other factors like the level of rust, cost of repairs, and structural integrity of your car can also help you decide whether a fix is worth it.

Will WD-40 stop rust from spreading? ›

It won't CAUSE rust, it will form a protective barrier to oxygen in the air, preventing further rusting (oxidation). It can't displace rust already on the surface, so cleaning the item prior to application will work much better.

Can I paint over rust on a car? ›

Now we're sure you want to paint over that unsightly rust. Use Rust-Oleum 769 Damp-Proof Primer as it needs minimal preparation, and penetrates the rust all the way to the metal! You can apply it on slightly moist or dry surfaces, for durable corrosion protection.

Can I buy a car with rust underneath? ›

Broadly speaking, you shouldn't worry about the surface rust that develops on underbody components, such as parts of the suspension and exhaust systems. This is a relatively minor problem that can be easily remedied with a wire brush or sandpaper; it doesn't affect the car's structure.

How much does rust devalue a car? ›

Rust affecting your car's frame and chassis can result in a loss of 20% or even more, as the integrity of these metal parts could be compromised. Structural rust risks the car's safety and longevity, which significantly impacts its value.

How do you check for undercarriage rust? ›

When checking for rust, try to get the car up on a lift to get a better look. If this is not possible, prepare to get a bit dirty as you slide under the car. Using a flashlight, look at any piece of metal you can. Don't forget to check door, hood, and trunk hinges and their molding areas as rust can appear there.

What does rust on a car look like? ›

Rust begins as tiny bubbles or blisters in the car's paint. Over time, these bubbles increase and eventually burst, revealing a reddish-brown spot underneath. These spots are the visible result of the oxidation process.

How to detect rust under paint? ›

Flash thermography is a reliable method for detecting hidden corrosion beneath paint layers. By utilizing heat pulse excitation and analyzing the resulting thermal response, flash thermography enables the identification of concealed corrosion.

Where do you see rust? ›

Rust is a common sight in structures where its structural strength comes from iron, steel, and other kinds of metals. Depending on the metal, these yellowish-brown or sometimes reddish patches emerge as a result of oxidation, which is usually caused by the presence of moisture and dampness.

Is it OK to buy a car with a little rust? ›

Is rust okay on a used car? It depends on where the rust is. Although most modern cars are designed to not have issues with rust, older used vehicles may still develop some rust. Surface rust is a cosmetic issue that can chip a car's paint.

What are the early signs of rust on a car? ›

Rust can occur anywhere on the body of a car. In fact, surface rust is often the tip of the iceberg, as it's common for oxidisation to form inside a panel or part and work its way outward. The most important thing to look out for is any exterior paint-bubbling. This is often an early sign of rust.

Is rust protection worth it on a used car? ›

As you can see, it's definitely worth it to rustproof your car! You can protect your vehicle (old or new) and keep it looking great for months (or even years) to come. If you don't want to rustproof your car yourself, you can ask a professional to take care of it!

Does rust check work? ›

Rust Check has a long history of successful automobile rust protection. Time Tested and Proven since 1973. Recipient of the 1997 Consumers Choice award for Automobile Rust Proofing Service.

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