My wife's 1991 420 SEL started running 10 degrees warmer than normal with flucuations on the gauge. My first instinct was to replace the fan clutch. That seemed to cure the flucuations but it still runs too hot. I talked to a reputable mercedes mechanic in Costa Mesa Ca and he told me that 3 out of 5 new fan clutches are defective. When he replaces a fan clutch he buys used ones and has better luck. Any ideas out there? The car has no leaks and a new radiator. Thanks in advance.