Hi,
I have posted on this site once before regarding my 2004 CLK coupe - here's a new one. After a drive, and the car has had a couple of hours to cool down, I notice a screeching sound I believe is coming from the A/C compressor. Its a pretty loud, medium pitched, metal on metal vibrating sound. The period between screeches is usually a couple of minutes, but it is somewhat unpredictable. When the car is running, or fully warmed up, or fully cooled down, I don't notice the sound at all. With the car at just the right temperature, if I grab hold of the large hose that goes from the compressor to the condenser, I can feel it vibrate in cadence with the screech. I unhooked the battery negative terminal to make sure it was not something electrical, and it is not. I also thought it might be something related to the radiator pressure being just right, but I was afraid to take the cap off the coolant to depressurize the system. I would take the car right to the dealer, but I know, because it takes so long for the problem to show itself, they are going to have a hard time diagnosing it. Any ideas?
Thanks,
John