Hello y'all. I'm new to this board, and I must say I am impressed at the quality information being shared here.

Now, my 95 C280 has been running hot lately, with temperature rising above 110C on city driving and the aux fan not coming on. Usual temp range has been 80 - 90C under fairly mild Nor Cal conditions. Mechanic feels that my fan clutch is not engaging properly, and I am curious as to what is the function of a fan clutch. Also, is this an expensive job?

The clutch fan should engage at 92-94C deg. The aux fans are supposed to come on at 107C deg. With the A/C on the aux fans should run at a lower speed that with engine heat.

Thanks M.B.DOC for the useful info. Now, what does it mean when the fan clutch is not engaging at the proper temperature? What needs to be replaced to get the fan clutch to function properly? Do I need to change the fan clutch itself? I am a novice here, so please bear with me. Thanks.

The fan clutch cannot be repaired. Look up a new vicious fan clutch in the fastlane. They are extremely easy to install. Also make sure your electric fans come on.