Exhaust noise only while driving, PLEASE HELP ASAP.

I am about to buy 1998 Crown Victoria, it has 138K on it, it does have a small exhaust leak up by the engine compartment upper pipe probably, not loud, you can only hear it while driving, not when parked, is this a common problem with this cars?, can that be anything major to fix or a sign that engine is going bad, I was driving the car today, it has the power, Please let me know what excatly i should look at tomorrow when buying the car and what the problem might be. I appriciate any help, thanks in advance.

An exhaust leak is not a huge problem nor is it a sign that the engine is going bad. I don't know if it's common for a crown vic, I don't think it is, but it's probably a minor leak (if the noise is not loud like you say, the louder the sound, the bigger the leak) in the exhaust manifold and it shouldn't be too costly to repair. My 85 impala had an exhaust leak on both manifold's and they were pretty bad leaks and I think it cost about $250-$300 to fix. Hope that helps.