Can anyone diagnose this overheating problem

[Barnsnake]

Why put the thermal switch for the fan in exit side of the radiator? The temperature of the radiator is of secondary importance. It's the temperature of the engine that matters.
By the time the temperature on the "cold" side of the radiator reaches the trigger point, the water coming from the engine would be critically hot (assuming the radiator is working).
There's generally an extra tapped hole in the intake water passage near the thermostat. Put the fan trigger switch there. If you are using one of those between-the-fins radiator temp switches, put it as close to the incoming water as possible.

[rtstrack]

I have a new symptom to add to the mix that may possibly be pointing to my pulley ratios. I went out for a ride tonight and noticed something very interesting. At 2900 rpms or more, the gauge was reading 200...anything under that....say 2000 or so and the gauge quickly shot up to 230....get onto an open patch of road and get the rpms back up and the temp dropped. Does this mean that I need smaller water pump pulley?

[Barnsnake]

I would expect a pulley ratio issue to manifest itself at a lower rpm.
It might still be instrumentation. As Cowtown noted the temperature gauge may be subject to variations in voltage. If you have a voltmeter, it might be interesting to note any change in system voltage around 2000-2900 rpm.
Also try downshifting to bring up the revs while operating at the same speed. This will tell you if it's RPM or air flow related.
Please verify that gauge and sender before beating your brains out on this.

[CHANMADD]

The reason for putting the switch on the cold side is that the thermostat controls the temperature of the water ,not the fan. The fan is only there for when the airflow is not sufficient enough to cool the water in the radiator.
So if you measure at the cold side and the water is hot ....the switch then tells the fans that there is not enough airflow and the fans need to switch on and take over and create the airflow. Then as soon as the water coming out the radiator has cooled the fans switch off!!!!
If the switch is on the hottest point of the engine the fan will run all the time..........WRONG!!!!.
The cooling system seems to be the most confusing to people..
Also remember that operating temps of 110 are not dangerous and in fact the thermal efficiency of the motor is better the hotter it is.
John
Buy a Jacket!!............................and a cap!

[Sharroll Celby]

110 is Celsius? What is that in Fahrenheit?

[Barnsnake]

If the thermal switch for the fan is set slightly higher than the thermostat temperature the fan will only come on when the radiator isn't receiving enough air flow to do the job. My fan only comes on when I'm idling along in traffic or stationary. The engine temperature rises 5-10 degrees (F) above the thermostat temperature then stabilizes or comes down when the fan triggers.
Again, I'm concerned about the temperature of my engine, not some mid-point that varies with air flow and ambient temperature.

To each his own.

[CHANMADD]

So ...Barnsnake, you are one of those that don't understand.
Water boils at 100 Celcius or 212 F
RTSTRACK, The 160 thermostat that you have in now works like nothing more than a restrictor plate because at anything over 160 its open!! so the water is going through the radiator so fast....even faster with your HiPo water pump ,that it has no chance to cool down.
The temperature of the radiator IS CRITICAL, and needs to remain cooler than the engine so that it can cool the engine.What do you think cools the engine???????
The fans should only come on at speeds lower than 15-20 mph anything over that and the airflow from the forward motion of the car is more than the fans can supply.
John