Cooling fan issues......PLEASE HELP

Only a guess, but it's possible the AC is overcharged. Especially something to consider if you've only recently gotten into some really warm weather, as the hotter it gets, the greater the pressure from the Freon (or whatever they call it now).

 

My only other thought is that 60 Series Detroits rely a lot on the amount of air being blown through them by the Turbo to maintain proper cooling. I'd check the charge air system for a serious air leak. I set mine up so I could do that myself. All it takes is a tubeless tire valve stem inserted in the aluminum pipe on the cold side of the cooler above the intake manifold and a 4" PVC pipe cap put in the line just behind the turbo and clamped in place. With transmission in neutral, the air pressure in the cylinders will rotate it to a point where all intake and exhaust valves will be closed, allowing you to pressurize the system. Sytsem should hold 35 psi with no noticeable air leaks.

 

One other idea: The fan clutch requires air pressure to hold the clutch disengaged. If there is an air leak in the line between the solenoid and the clutch itself, it will lose pressure and the spring will overcome the air pressure keeping the clutch dis-engaged.

 

Yeah and it might not leak with the engine off so you won't ever be able to hear it. Mine won't. Or it could be bad/corroded connections from the harness that hooks into high pressure switch.

 

Please post findings. I have the same issue with my c-15. May put me on the right path.

 

And it threw NO codes?