Creaking Front End Noise--Only in Hot Weather

My 2002 LS V6 starts making loud "creaking" noises (mechanical in nature) but only after I've driven it for a while and ONLY in the hot weather (above 85 degrees or so). The noise does not seem to be related to road or driving conditions--once it starts, it doesn't seem to be related to how fast or slow I'm driving, whether the road is smooth or bumpy, whether I'm turning or going straight, etc. It seems to be strictly related to outside temperature--when the thermometer hits the 90s (fortunately, not that often in the Chicago area) the car groans, creaks and occasionally makes small clicking or popping noises that, so far, no one has been able to trace. I've taken it to my mechanic and also to the L-M Dealer and both have said they can't find anything wrong including checking the usual things like the suspension components, tie-rods, ball joints, brakes, etc. I've read most of the other threads on this Forum, but other similar front end noise problems seem to be at slow speeds or while making turns and none have mentioned anything about being intermitent depending on the outside temperature. It's crazy--the car performs well and is still very quiet (considering it has 91,000 miles) except on real hot days when it's very noisy and makes me wonder if it is safe to drive. Any advice (other than hope for cooler weather)?

Are you able to determine the approximate area the creak is coming from, such as front or rear? Possibly a dry u-joint if from the middle of the car, or bad CV joint if from the rear. There are various other suspension joints in the rear as well.

It sounds like you need to find a shop that has a Steelman Chassis Ear system to isolate the noise. The Chassis Ear consists of up to 7 clamp on microphones, a pair of headphones, and a switch box/amplifier that allows you to switch between each of the microphones. When you find one that the sound is loudest at, move the other 6 microphones to that area, and continue this process to pinpoint the noise.

-Rod