look,
Your water temp sensor is in the head, driverside between 1 and 3. It reads the temp of the coolant. If its reading 220 degrees, you hose down the radiator and it quickly drops to 160, the liquid end cooling system is working properly, the radiator is flowing and the pump is moving water, its the only way the temp would drop that fast with you just spraying the radiator.
The obvious answer, is that the air dam and shroud, or the lack thereof, IS causing the issue.
The air dam directs air onto and through the radiator when the car is moving, cooling it, it does nothing when its sitting still. These cars are bottom breathers and without the dam they will overheat. The fan pulls air through the radiator when the car is sitting still, and has less effect when the car is moving, thats why, usually, the fan only turns on when the car is in traffic or stopped.
Now the issue here is that with the mechanical fan is lacking its shroud, its just pulling air from in front of the radiator, through the blades and onto the motor, not doing jack for cooling. With a shroud, the fan will pull air through that radiator thus cooling it! TaaDaa!!
You need the dam and the shroud or this will continue. being lean can cause it to run hotter, but not like this.
also, how far form the radiator is the fan? it need to be pretty darn close.
I understand this is you DD, but if you keep overheating it and not fixing the problem, you are going to eventually cause permanent damage to the motor.
When are the air dam parts and shroud coming? after you swap head gaskets, i would not drive the car until they are on.
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Nexium Lawsuit