According to Mercedes Benz Star Bulletin #P-B 27.55/50f, dated March 24, 2006, there is a problem with Valeo radiators up to production date 9/2003 installed in models:
203.040/061/064/065/081/084/261/264/281/284/740/747/746 also
209.365/375/376/465/475 and finally
211.065/070/076/083/265/283
The problem occurs when the coolant leaks from the defective radiator through the cooler tank into the tranmission, resulting in damage to the tranmission and torque converter. Unlike earlier types of coolant and tranmission fluids synthetic coolant and tranmission fluid mix very well together. Mercedes does offer a test kit to check for the presence of glycol in the trans fluid, but this test is expensive and even if the test is negative at the time there is no gaurantee that a leak won't occur later. In event of transmission failure it is STRONGLY recomemmended to replace the radiator as part of the repair on any of the above listed automobiles.
This is nothing new, it's affects other cars like the CLK also. I think it's just MB's way of punishing people that buy cars with automatic transmissions. It's not a big deal, if your radiator leaks into the tranny, it's only about $10K to fix it. If you are really concerned, just replace the radiator, it's under $200 for a brand new one, just make sure it's a Behr and not another Valeo.
Here is a lab you can send a sample of tranny fluid to for testing and I think it's not that expensive, $23 - Blackstone Laboratories
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