I have 1993 Honda Civic 1.5L SOHC. I've been having over temp problems for awhile. I've changed the thermostat twice, acid flushed radiator, and changed out fan switch at thermostat housing. When I know the antifreeze is topped off the temp is usually fairly steady, occasionally the heat doesn't come right away even when engine is warm. After about a week after topping antifreeze off and driving it the temp comes back up and it fluctuates up and down. I've also noticed that the fan on the radiator does not come on when the engine is over temp. I've confirmed that the fan operates and the temp switch has no continuity when cold, and continuity when hot (that was a pain in the ***). I know the water-pump was changed out about 40K miles ago, but it does howl. Also, I more thing i've noticed is if the fan does come on at over temp there is no flow through the radiator, there is nothing but cold air coming off the radiator and when I squeeze both the upper and lower hoses I don't feel any flow through the hose. When I turn the car off the upper radiator hose get extremely hot and is under allot of pressure. Could an air lock at the upper hose capable of causing all of this or the water pump failed? I can't find any leaking at the weep holes at water pump, the heater core doesn't appear to be leaking, I think I'm losing my antifreeze at the overflow container but I can't seem to be able to verify that. Currently I'm planning to remove the water-pump but I would like to know what you think? Oh yeah motor oil is clean, no antifreeze there. HELP!!

 

Your leaking somewhere. If the overflow container is overfull but the radiator is empty it's probably a bad radiator cap, or an air leak in the hose between the two. Or it could be a leak in the engine letting gas out of the cylinders push the water out of the radiator.

Don't keep driving with a howling water pump, it'll seize up and strip the timing belt and then you've got a big problem.