And every year, he tells car owners the same thing.
"It's like a vacuum cleaner, basically," Johnson said. "It's going to pick up that water and suck it right in. And it's going to get inside your engine, whether you want it there or not."
Johnson said even if you drive through a few inches of water, it can still cause damage.
"A lot of modern cars, the air induction systems are so low to the ground," he said. "It doesn't matter if it’s 6 or 8 inches of water---It can cause a problem to your vehicle.
"The car is made to run off air and light fuel mixture, nothing like a complete liquid. So it locks the engine up when it ingests that much water."
The rising Ohio River has swallowed many cars across Louisville, and after the waters recede, it's time to keep a closer eye out if you're buying a used car.
"Look under floor mats if you can pull parts of the interior carpet back, because a lot of people don't go that far when they are trying to clean a flood-damaged car up," Johnson said. "Look at the bolts of the seat---See if they're rusty. A lot of that stuff has a very light film on it. So if water gets on it, it takes that film off."
Some drivers may get lucky and be OK, but driving through water could be an expensive gamble. Experts recommend that if you have a question about whether a car might be flood-damaged, call an independent mechanic to have it checked out.