Crackling Noise From Exhaust System

[DB S600]

Hello everyone:

I am the current owner of a 2004 Lexus LX470 with close to 20,000 miles. I have owned the vehicle since new and I will have had it exactly one year as of June 18th. In this past year I have had numerous problems with the vehicle which have included the replacement of (1) a major front suspension component (If not mistaken, I believe it was a torsion bar), (2) the HVAC blower unit, (3) faulty rear sensors for the EAS, and most recently (4) brackets for the entire (left and right) center row seats. This is my first Lexus product and for many years I refused to consider the make – until I was recently sold on its “supposed” undeniable reliability.

At this time I have another problem… There is a constant “crackling” noise coming from the truck’s exhaust system. When the car is on (w/ and w/o A/C turn on), the noise is evident whether I drive the vehicle for short or long distances, no matter the weather (outside temperature). When I shut the vehicle off, you are able to hear the crackling for an extended period of time.

After taking my vehicle to the dealership, last week, I left extremely dissatisfied. The service manager said that this is a completely normal noise having to deal w/ the expansion and contraction of the exhaust system as a result of metal tubing heating and cooling. He even went on to show me a completely brand new LX which was lifted – another tech proceeded to rev the engine for about 2 minutes and then he turned the vehicle off. The service manager and myself then stood under the truck, waiting for the noise to occur. It took about a minute, but this “new” truck started to posses the same crackling noise – however, not nearly to the degree that my vehicle has shown. The service manager then went on to say that the noise might increase in loudness / amount in a year’s time – explaining the reason that my LX had a more prevalent noise.

Upon returning home, I began to recall that many of my previous new vehicle did have the same noise (but not nearly as much) – HOWEVER this noise ALWAYS went away as the car was broken in (I would estimate at about 2,000 miles). Yet it has not dissipated on my new LX.

Does anyone else know what can explain this noise? Is this a normal noise? Does anyone else have a similar problem with their late model LX? To best explain the noise – it is a popping / crackling noise that comes from underneath the truck at its midsection (between the driver’s and passenger’s doors). It sounds as if a liquid (oil on a pan on a kitchen stove, for instance) is popping - but with more of a clinging effect (metal knocking against metal)

Thanks so much for any and all input – and my apologies for the long post, Javad.