Quote Originally Posted by Aveo5_boy View Post
I thought I would pass this info along as i was browsing through the Chilton Manual.

Engine overheating checks from Chilton Manual:

Check for a loss of the coolant.
Check for a weak coolant solution.
Check the front of the radiator for any dirt, any leaves, or any insects.
Check for leakage from the hoses, the coolant pump, the heater, the thermostat housing, the radiator, the core plugs, or the head gasket.
Check for a faulty thermostat.
Check for retarded ignition timing.
Check for an improperly operating electric cooling fan.
Check for radiator hoses that are plugged or rotted.
Check for a faulty water pump.
Check for a faulty surge tank cap.
Check for a cylinder head or an engine block that is cracked or plugged.
First of all, thank to you to everyone in this thread who has posted and thank you Aveo5_boy for typing that out for me.

Good news: I found the leak. The small outlet of the thermostat housing is leaking, looks like an easy fix. The leak was too slow and did not leak under idle/2,500 RPM when parked so I didn't notice it before, but before the thermostat housing and down I can see the previous drops.

Bad news: The leak is small and isn't the cause of the overheating.

Check for a loss of the coolant. - Leak is small, found it.
Check for a weak coolant solution. - Nope.
Check the front of the radiator for any dirt, any leaves, or any insects. - Nope.
Check for leakage from the hoses, the coolant pump, the heater, the thermostat housing, the radiator, the core plugs, or the head gasket.- Leak is small, found it.
Check for a faulty thermostat. - I assume the thermostat is working because the upper hose is hot, and the temperature is hottest the at the upper hose/upper part of radiator, and cools down further down the radiator. The heater also works.
Check for retarded ignition timing. - Not sure how, but car "runs" fine.
Check for an improperly operating electric cooling fan. - Fan runs fine at a stop/in traffic and the problem also happens at highway speeds.
Check for radiator hoses that are plugged or rotted. - On my initial check everything looked fine.
Check for a faulty water pump. - Heater is working, and coolant temperature (tested with IR thermometer) goes from hottest to coolest from upper hose > top radiator > bottom radiator > lower hose, so I assume the circulation is working.
Check for a faulty surge tank cap. - Only cap is the pressurized reservoir cap, which I have already replaced.
Check for a cylinder head or an engine block that is cracked or plugged. - Can't see anything on the exterior, seems possibly out of my expertise but I am not sure how to check.

Other things to consider:

The temperature gauge slowly climbs to the red line. Turning the heater on brings it back to normal levels.