I have a 2000 civic ex 5 spd and when I got it the first couple times I drove it the coolant reservoir would overflow with boiling coolant, so I did everything I could replaced all related hoses, radiator and t'stat and now I've been driving the car every so often and during driving I have a scanner open that reads engine coolant temp, the coolant temp rises to 180 then sits there until I start to slow to and idle, then it rises to about 186, but if I continue driving the coolant temp stays level between 174-183 degrees Fahrenheit. when I stop driving the car the coolant temp starts to rise slowly, the other night it reached 220 Fahrenheit and then stayed there for about ten minutes then started to rise again to 225. does this seem normal or could this indicate a head gasket leak from a coolant passage, or problem somewhere else. the hoses and t'stat housing are not leaking from what I can see and the radiator looks dry every time I inspect it after a driving session. i just want to know if a should stick it out just a little longer and see what happens or if this is clearly indicative of a head gasket failure or failure somewhere else

 

update: drove it last night and the ECT got to 243 then dropped rapidly down to 207 -214 then i parked and it went up to 235 is the horrible please let me know

 

It is not normal for coolant temperatures to reach 220+ degrees F. If you don't see any evidence of coolant leaking, such as spraying under hood, chalky residue around coolant hose areas in the engine bay, or puddles under the vehicle, then you must be burning coolant if the radiator is continuously dry when you check it. This would indicate either a head gasket leak or cracked cylinder head... but this isn't your only issue. The fact that the vehicle stays at or near operating temperature when you are moving and only overheats when you are stationary indicates either a bad cooling fan/system, or if the fan works, the polarity of the motor is backwards (it MUST blow from outside the car to inside the engine bay) or you have a bad thermostat. If the thermostat is NOT on OE one from a Honda Parts Department... this should be considered suspect. All of these suggestions assume that all of your OE cooling lines/hoses are being used... nothing blocked or eliminated (especially the bypass hose from the thermostat housing to the cylinder head).

 

the fan comes on at these temps and turns off around 205, the new thermostat is an OE Honda Parts Department Thermostat. what do you mean by the polarity of the motor? ive drained the oil twice and its not chalky or brown at all.

 

Your fan motor has a positive and a negative wire going to it. If you swap the wires in the plug, the fan will spin the other way. What you need to check is when the fan comes on, the air is BLOWING into the engine bay... not toward the outside/front of the car. If it is... the wiring is good... if it isn't, swap the wires so it blows the other way.