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You are sitting on a time bomb.
Testing Fan Clutch: if you want to keep your fingers, keep them away from the Fan Blade.
With engine hot and running, hold a piece of paper behind the Fan Blade, it should "flap", indicating that there is adequate air flow.
There are countless people with blown head gaskets b/c of failure to do a cooling overhaul.
In fact, I would not be surprised the #1 cause of death in an E39 is blown head gasket.
Last edited by cn90; 01-21-2013 at 10:43 AM.