Hundreds of motorists have complained to the feds that the bottoms of their older-model Nissan Altimas are rusting through, potentially putting their feet awfully close to the road. It sounds like a scene out of a certain cartoon set in Bedrock, but the drivers say there is nothing funny about this problem. "I'm not Fred Flintstone. This is not a good thing," Marie DeMaria, a Chicago-area realtor, told NBC News after her mechanic examined the corrosion on the floor pan of her 2005 Altima. Read MoreTesla delivered 10K cars in Q1 "This is not safe. I drive every day for a living. This is very nerve-racking for me to be driving now."

Hundreds of Nissan owners have complained about their 2002-2006 Altimas rusting out. Source: NBC News

The National Highway Traffic Safety Administration (NHTSA) has received more than 400 complaints of rusted-out Altimas rolled out between 2002 and 2006. Some came from states that have heavy snow, where road salt can eat away at metal—but not all of them. And Nissan Maximas from the same period had far fewer complaints. The cause is unknown, though several mechanics told NBC News they think a design flaw may be preventing water from draining, causing floor pans to rot from the inside out. Read MoreSelf-driving cars still this far away Nissan said it has no plans to order a recall and notes that corrosion in older cars is not unusual. "This issue is not considered a safety defect by Nissan or the government agency that administers safety recalls," the automaker said in a statement. Although only one injury related to a rusty Altima has been reported to NHTSA, DeMaria's mechanic, Zoran Sarich, said the potential for more exists. Read MoreThe new McLaren 'Black Swan revealed

"Sooner or later, you're going to be able to put your feet through the floor," he said. Sarich said DeMaria's car wasn't the first Altima he had seen with a rusty floor. "I have a couple of other customers with the same exact car and the same issues," he said.