2009 2500hd New Fan Clutch not engaging on long hill climbs

[ramathies]

Just put in a new fan clutch but it will not engage on a hot day pulling a trailer and pulling a steep grade.  It seems to engage on start up as normal but is not working while towing pulling a hill.

[diyer2]

Bad part.

 

[newdude]

Perhaps you were used to the operation of the bad one that was replaced?  Did you get a GM clutch or aftermarket?  Are you getting any overheating?  

[ramathies]

Just put a new GM Clutch in, comes on when you start it up and runs for a while, then goes off so I think it is operating right.  Got overheating the first time I towed since replacing the fan clutch, 87 degree day and pulled a steep hill, overheated to about 230-240 and the fan never cut on.  I guess it could be the cooling stack needs to be cleaned but did that 60k miles ago... must be clogged again... not sure why it is clogging up so often.