I have a stock 69 Z-28 cooling system with all components as original with the exception of the removal of the smog pump, now using a shorter 7440 XL gates belt. Was having a heating problem at low speed and idling in hot weather conditions. The fan clutch was an Eaton unit purchased over the counter from GM in the 70's. Noted that the fan would free spin for many revolutions after engine shut down with a warm engine. Determined that the fan clutch was faulty and sent it to a respected restorer/rebuilder for overhaul. Received it back and overheating issue went away. Now I am noticing squealing which I believe is belt slippage above 4500 RPM. Belt has been replaced and is tensioned properly; all pulleys appear to be in good condition. I am suspecting that the fan clutch is not disengaging properly causing high belt loads at high RPM. In John Z's cooling article, referring to fan clutches he stated, "most of them essentially disengage over 3500 RPM" Sorry this is so long. Any thoughts?
