Numerous media outlets are reporting that the National Highway Transportation Safety Administration is investigating more than 5.1 million Jeep Grand Cherokees and Jeep Liberties for a possible high incidence of fires after rear-end collisions as well as corrosion problems.

This investigation should be taken into consideration before completing the purchase of a used Jeep Grand Cherokee or Jeep Liberty.

According to The Detroit Bureau.com, "The National Highway Traffic Safety investigation, launched in August 2010, initially focused on 3 million Jeep Grand Cherokees produced between 1993 and 2004. The agency has now added another 2.1 million 1993 to 2001 Jeep Cherokee and Jeep Liberty SUVs."

According to The Detroit Bureau, "The problem appears to center around the rear-mounted placement of the plastic gas tanks used in the three models which may make them more vulnerable to catching fire. NHTSA has so far received reports of 15 deaths and 41 injuries related to the potential problem."

Here is what Chrysler had to say in response to the investigation, which it is reminding owners and potential buyers is still an investigation and not a recall. "Chrysler Group is cooperating fully with NHTSA regarding an investigation into 1993-2004 model year Jeep Grand Cherokee, 1993-2001 Jeep Cherokee and 2002-2007 Jeep Liberty vehicles. It is important to note that this is still an investigation, not a recall," the statement said.

It continued, "In connection with this investigation, Chrysler Group studied publicly available data involving more than 21,000 rear impacts in the original subject vehicle - the 1993-2004 Jeep Grand Cherokee -- and peers. It is apparent from this study that rear impacts resulting in a fire are extremely rare, rear impacts resulting in a fire occur no more often in 1993 - 2004 Jeep Grand Cherokee vehicles than in peer vehicles and the 1993 - 2004 Jeep Grand Cherokee vehicles are at no greater risk of exposure to fire in rear end collisions than peer vehicles."

The statement ended with this. "Accordingly, Chrysler Group has concluded that 1993-2004 Jeep Grand Cherokee vehicles are neither defective nor do their fuel systems pose an unreasonable risk to motor vehicle safety in rear impact collisions. We would expect that a similar analysis of subject vehicles recently added to this investigation would support a similar conclusion. The 1993-2004 Jeep Grand Cherokee and other subject vehicles meet or exceed all applicable federal motor vehicle safety standards and have excellent safety records with hundreds of billions of vehicle miles driven."

Nothing in this article should be seen as a blanket condemnation of the Jeep Grand Cherokee or Jeep Liberty. It's more a recommendation that potential buyers should talk to their mechanics or other knowledgeable people (like body shop owners, firefighters who respond to collisions, or police officers who investigate accidents) about the vehicles before buying. For example, I always recommend an independent pre-purchase inspection of any used car. Those inspectors have seen a lot over the years.

The Detroit Bureau, which is helmed by respected automotive journalist Paul Eisenstein, also points out that Jeep Libertys have potential problems independent of the risk of fire. It reports, "According to the National Highway Traffic Safety Administration the lower control arms in Liberty's rear suspension can experience excess corrosion that can cause them to weaken and break. In such a situation that could lead to a loss of control and a possible crash, NHTSA warns."

That's going to be an easier problem to detect. A good pre-purchase inspection is going to determine corrosion problems like those mentioned by NHTSA. Mention that concern to the inspector. A good one is going to look for the problem but it never hurts to mention it to him or her.

The Jeep Liberty corrosion concern isn't going to be as much a concern if the vehicle has spent its lifetime in areas of the country not prone to rust (like the Southeast and Southwest, as well as Southern California for example). You can determine where the vehicle has been by requesting a vehicle history report.

Also, just because a Jeep Liberty has come from Ohio, for example, does not mean it is an automatic candidate for corrosion problems. Well-maintained vehicles that were regularly washed during the winter should not be as affected. Regular washing would have reduced the build up of harsh materials like road salt that would eventually lead to corrosion problems. Vehicles housed in states that require winter road clearance are going to be the most likely culprits for corrosion problems.

Should the Jeep Grand Cherokee and Jeep Liberty NHTSA probes give you pause? Absolutely. Should they stop you from buying a used Liberty or Grand Cherokee? Do your homework, get a good pre-purchase inspection, and you reduce the risk of potential problems.