2000 honda civic si. STOCK ENGINE 164,000 miles
New plugs, Dist. cap, Coil, rotor button, o2 sensor, and cat. This all cleared CEL. Been running great. 36 mpg great.
Tuesday looked at Temp needle and it was hair under H and hit Redline once before I could pull over.Turned on heater to relive heat.(always heard to do this but don't know it helps any) Long story short, after 6 stops to cool engine and limp home, I changed T stat and that wasn't it. Try to turn heater on and cool air comes out. Top hose on rad is hot as hell and bottom hose very cool. I'm thinking water pump. Old antifreeze looked pretty good when i drained it, not good as new though. Hoses are not collapsing. I guess it could be radiator. Inside looks clean though. Just wanted some opinions before I tackle this job. Thanks in advance....

 

Just for info, your fluid should have been changed 3 times, my 02 civic had its fluid changed 2 times by 90k had 100k warranty so had honda do my service. if upper hose hot and lower cold, you may be correct to say water pump. ( changed mine at 102k with timing belt ) Also check to see if your fan is coming on when temp gets to where you know it should be at. The fan motor could be bad or the temp sending unit is bad.

 

Changed water pump yesterday and finished today.(had to wait on parts) Found broken left lower motor mount. New belts throughout pulleys. Water pump didn't seem to be bad but now it's changed. Radiator fan was working intermittently so it got changed to. Seems to be working fine. So do not really know which part fixed the overheating. If i had to guess i would say fan.

 

since you have changed all the parts that could cause heating, this is good, now you will not have to worry for a while. Just keep track of what you fix and know in the future what other items may come up and do it ahead of time, this will keep your car in good shape all the time and you won't have to worry about failure. Enjoy your ride.