OP, you better fire your mechanic. Thermal clutches like ours are supposed to be locked up when the engine is off or cold. the squeal has gone away because you have changed the alignment of belt when replacing clutch.
A thermal fan clutch is engaged on a cold startup because the fluid drains into the working area when the engine is shut off.
Thermal Fan Clutch
- Varies the fan speed with temperature of the air behind the radiator.
- Engaged (high speed) operation provides maximum cooling.
- Disengaged (low speed) operation provides fuel savings and noise reduction.
- Greater life expectancy than a non-thermal clutch.
- Briefly engaged at cold start-up.
- Engages at about 170° radiator air temperature, (about 30° lower than coolant temperature).
The air temperature coming through the radiator is sensed by the bi-metal thermal spring on the front of the thermal fan clutch. It expands and contracts with the change in air temperature operating a valve inside of the clutch. When cold, the silicone drive fluid is pumped from the working area to the reservoir. When hot, the valve opens allowing fluid from the reservoir to be transferred to the working area thereby increasing the fan speed. The clutch disengages as the air temperature decreases, closing the valve and allowing the silicone fluid to be pumped back into the reservoir.
A thermal fan clutch is engaged on a cold startup because the fluid drains into the working area when the engine is shut off. The fan clutch will slow down shortly after startup as a result of a pumping action produced by a difference in speed between the shaft and the body of the clutch.
Most models are designed to duplicate original equipment performance. Some Chevrolet/GMC truck models are specifically designed to engage at lower temperatures than the original equipment parts that they replace.