I have an '87 300D 124 sedan, and have just replaced the water pump assembly due to a leaking shaft seal. It noticed that it also had a viscuous cooling fan drive.

I need some advice on how to test this viscuous fan drive, and how to check and/or maintain it too. Do I need special tools and/or lubricants for this fan drive? So far, the engine temp is normal, and nothing seems to be wrong with the fan and drive.

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Jake