P1800 es runs hot!!

I empathize with the other gentleman with the overheating problem. I'm getting a hot reading (creeping into light red) on the water temp gauge. The reading slowly climbs, esp. while idling, steadily, until it begins reading hot. The reading stays at about there, right on that green-light red boundary. It happened seemingly all of a sudden while idling on the freeway, at least that was the first time I noticed. The engine has been rebuilt less than 20,000 miles ago, and I had just replaced the FI water temperature sensor and the FI throttle valve switch.

I've had the radiator rodded out, new coolant added, inspected the water pump newly installed about two years ago, checked the thermostat on my stovetop (and even ran it without it), replaced the temp gauge temporarily with an aftermarket unit to insure proper reading, secured the viscous fan temporarily to verify it wasn't slipping.

There is a 'secondary' temp gauge added post-thermostat by a former mechanic, and that one isn't getting above 180 degrees. That reading was verified by another mechanic who monitored the temp at the radiator for over an hour. It was showing hot at the engine block water temp sensor, but not at the radiator. He thought the gauge was bad, but swapping it shows it's still getting hot up at the rear of the engine. He found no fault with the engine, felt it was running fine. The timing is at 10 btdc according to the mark. Could the mixture from the FI be so off as to make it run hot?? Anything else I could check with the cooling system? THe mechanic felt it was cooling fine.

ANy help appreciated.

Thanks,

-Ed