Over the past two weeks my wife and I drove from Arizona to Indiana and
back in our 1991 Vanagon GL Westfalia Camper. It was roughly 4,000 miles of
driving. The engine is the original 2.1 liter with 177,000 miles on it. The
factory air conditioner works and was used during much of the drive. During
the first half of the drive we noticed that the radiator fan began to make
a grinding noise. The noise is most obvious with the air conditioner off
while stuck in stop-and-go traffic. This results in periodic cycling of the
fan from off to on. The grinding noise lets me know that the fan is
rotating but the sound is unfamiliar and our opinion signals a problem.
Based on the GoWesty article titled "Cooling System in Vanagons: Explained"
I am convinced I have a 450-watt radiator fan motor that operates at three
speeds. I believe the grinding noise is most obvious at the slowest
fan speed. And finally, here is the question. What action should I take, if
any, to address the grinding noise I hear from my radiator fan?

Thanks,
Ryan