Checking for salt damage

I’m looking at a 2009 car in a couple days that had an original owner in Wisconsin and I’m concerned about salt damage leading to rust in the future. I’m in Seattle and we don’t really salt our roads here and I know that when the dealership got the car here from auction the undercarriage was washed.
I’ve requested they lift the car so I can inspect the undercarriage with a flashlight, but I’m not really sure what to look for.

Since it’s an '09, I don’t imagine I’d see much in the way of rust. What should I be looking out for under the car?


Check the frame and wheel wells. Also, check the strut tower mounting area.

Also check the brake & fuel lines, engine subframe, suspension components (especially in the rear) and the floor pan, especially where it joins the rocker panels. Also open the doors and check them on the insides at the bottom.

A light coating of rust is normal on the brake & fuel lines.

Someone published a “rust index” for North America. The North East, and area around the Great Lakes are the worst, while the desert areas are best.

Montreal, Canada is the worst city for rust, it’s 16 times as rust prone as the South Western USA. The West Coast is somewhere in between, but expect a Wisconsin car to only last half as long without rust compared to a Seattle car.

I lived around the Great Lakes and we worried about rust after 5 years of ownership, regardless of the rust guarantees. Nissan were the worst of the Japanese cars for rust, and by and large that is still true.

Look at the weld areas where the drain holes are in the bottom of the doors, front and rear quarters and the rocker panels. This is one of the FIRST areas on any car that will rust. Any bubbling of paint at and around these holes means there is definitely rust between the panels above. Look at the spare tire wheel and see if any coorsion from the inside which would indicate a leak. Likewise, peal back the carpeting and look at the floor board. Salt is carried from on your shoes to the inside of the car and contrary to popular belief, rust starts there as wel, and not only from the out side on the exposed undercarriage.

Any rust you see, is ten times more severe in areas that are impossible to see. All welded areas on trunk lids where the drain holes Should be checked as well as the fender liner and fender joinery. If you see ANY bubbling under paint on the lowest levels of the body, treat it like a rust through. A little proding with a small blade screw driver or punch through the bubbles will reveal it. Surface rust on heavy metal suspension components is seldom a problem on cars less then ten years old. It’s the sheet metal rust from inside that you cannot see and can do nothing about without treatment.

Also, check around windshield and rear window seal for bubbles. This area is near impossible to fix cheaply and you should run from a car with rust here. Chances are it will then be everywhere. Every car is rusting somewhere now in the salt areas of the country as we speak.

The good news is, given it’s age under 6 six years, if there is little rust, you can stop it all in it’s tracks in areas you can reach with motor oil. Otherwise, the body on all cars in this area will rust through at some point and be unsafe and worthless over time.

I’m in SE Wisconsin and would bet that this car has signs of rust on the underside already. How bad is anybodies guess.
I think the manufacturers cause the places for rust to begin, just by the way these cars and trucks are designed. The more they close up wheel wells, frame, and other areas…the more places there are for that salty water and slush to gather. Once it dries out the salt remains and as soon as the salt gets damp it eats away more. There is no way that they can keep all of the slush out and what gets past the wheel well liners…it’s held there, for it to eat away more of the car.


The worse rust on all cars occurs when salt water is washed on the car from above and enters the body cavities and collects on inside welds around the bottom of the car body shell. . It can never be washed away sufficiency on the inside and will stay there all year round, rusting. Exposed areas with obvious salt stain can be rinsed off with a low pressure garden hose. High pressure washers actually drive salt water back up into the body cavities through drain holes and through seals. Because drain holes are surrounded by welds which burn off protective coatings, salt brine and water collects there and these are the first areas that rust. Washing from the outside does little for where the worse rust occurs. I know looking at the undercarriage and wheel wells and washing these areas sounds like you are covering all the bases…but we are not. It’s only a part of the rust story, a relatively small part…

For road salt, areas that get splattered when the turning wheels throw snow and road debris backward are good places to look for rust. Focus on the underside, and the outside edges (where the wheels are) more than the center of the car.

For the upper part of the car, all the rain gutters and their drains (including for the trunk) and the route water that hits the windshield eventually drains off and gets out. Usually there are vents under the windshield that are part of this.

This is all fantastic information.
Thank you all for your help! I will search all of the locations recommended. Luckily there is the same car available for just barely more with about 20,000 more miles (still less than 100k) from a single owner here in the Seattle area, so if this car doesn’t pan out I have a backup plan.

Thanks again!

I would just add that a 2009 was probably built in 2008 and 6 years is plenty enough time for severe rust to develop.

Some Rust Belt cars end up here in OK that are not even 6 years old and in all honesty should be gutted for mechanical parts and the rest crushed.

Good to know. Thanks!

A little accident at the Morton Salt factory. Click on the ?

At least those cars won’t get rickets… what with the salt being iodized and all… {:slight_smile:

Since it’s an '09, I don’t imagine I’d see much in the way of rust.

Having grown up there I got a good chuckle out of the above. It’s going to have a fair amount of surface rust after the very first winter. And low mileage is actually worse when it comes to rusting out in that area. The perfect storm? Low mileage and a heated garage…if you listen carefully, you can hear it rusting :wink:

I remember the owners manual from my old SAAB 96 showed you where to pour your used motor oil into body cavity areas, allowing the oil to seep through the rust-prone areas. What a car! Quirky but really cool! Rocketman

At least those cars won't get rickets

I thought iodized salt prevented Goiters.

I wasn’t going to mention it, but…mountainbike is incorrect regarding the reasons for iodine supplementation.

Calcium and Vitamin D supplementation helps to prevent Rickets.
Iodine supplementation helps to prevent Goiters.

I do that still today and it works very well. It works on any car, not just SAABs. The old SAABs had very well made bodies and if rust and not mechanics were all you had to worry about, these cars could run for decades in the salt belt. A friend has several in show room condition, a couple over twenty five years old using the strategy. Strategically applied oil prevents rusting from occurring until it’s washed away which inside body cavities can take about two years. Now that they make a lot of biodegradable materials, there is no reason not to do it.

Btw, as a 2009, you may not actually see much rust…but it is there.

Carefully Look At Steel Brake Lines, Fuel Lines, Etcetera, Particularly Where They Are Clamped Or Supported. Too Much Corrosion There? Walk Away. Could Be The Canary In The Coal Mine.
If I Had The Choice, I’d Choose A Vehicle That Wasn’t Possibly Marinating In Brine For Several Winters. I Live In The Rust Belt. I Know.


Yeah Dag, I read you. I still have an old '78 SAAB 99, bought new and drove, restored in 98, now it’s in storage. I’m looking for another 95, 2 strokes are neat. Rocketman