Mitsubishi Repair: 90 ECLIPSE OVERHEATING, cold weather protection, antifreeze mixture

Question
I have a 1990 Eclipse with 1.8 engine,manual transmission. The head gasket had went causing coolant to leak. Coolant did not enter engine. It just leaked out on edge of head.  Replaced head gasket, in the process also replaced timming belt,& water pump. Engine runs great!
Next it started to overheat. So I replaced thermostat,pressure cap, and radiator. Cooling fans will operate. Went so far as to remove thermostat just to see if it was mabey stuck. Still overheats. While car is in garage idleing temp guage will stay right in middle. Fans will turn on and off to cool as needed. Once I take it on the open road guage will start rising. Any ideas what may be causing problem. Is there anything I could have missed?
Thanks
Kirk

Answer
Kirk,
It sounds like you've covered about everything.  You should be sure you're using the correct water/antifreeze mixture.  It should be a 50/50 mix for optimal hot weather and cold weather protection.

You may also need to make sure the system is free of air bubbles.  When you drained and refilled your coolant, you should have had your temperature control knob in your car turned all the way to HOT to be sure coolant in your heater core could flow.  You should 'burp' your coolant system by slowly squeezing the upper radiator hose as the coolant is heating up. Be sure the overflow tank is filled properly when it is hot and cold.  It is good practice to replace your upper and lower radiator hoses if you've never done that.  Those will go bad over time; especially if you're still using your original hoses.

But if you've done all that and you're still overheating, it's possible there is still a problem with your head gasket.  It's very possible the head bolts had loosened within that first week.  For proper installation, the head bolts should be retorqued because they have a tendency to work their way out depending on how much they were torqued when first installed.  So it would be a good idea to have the head bolts checked and tighten them if they need it.
Good luck!