Ok a got a 98 Accord EX Coupe (4 cyl AT) a month or so ago from a dealer in town,.. I started having some problems with it after about 3 weeks when the heater started acting erratic sometimes heating sometimes not and when it did it would go cold when stopping at a red light. Then the temp gauge started fluctuating where it would basically take a few minutes from a cold start (in the winter no less) to getting close to red line overheating. I took it back to the dealer since it hadn't even been a month since I bought the car thinking they would fix it or risk having to take the car back but they didn't have time to fix it till a few days after 30 days was over. So they said that it was overheating and the water pump was shot. I purchased a warranty with the car that covered 50% of the water pump cost, the dealer ate 25% and I the other 25% so it only cost me $150. Everything was fine till about 2 weeks later when I noticed the heater wasn't heating properly and then a few days later the temp gauge started acting like it was overheating again so I took it back to the dealer and told them what it was doing. They checked the coolant which was still full said the water pump was still working and that it was a sensor that was preventing the cooling fans from turning on and to leave the defroster on until it gets replaced otherwise it will overheat. So I went home all the way praying it wouldn't overheat with the heater/defroster on full blast which was only keeping the heat gauge a 4th of an inch from the red line. Today I drove it into town and the solution they told me at the dealer is no longer working and the temp gauge will jump up to past the red in 5 minutes while the heater will not put out any heat at all if only a little. What the hell is wrong!!??

 

Ok so it wasn't anything crazy just needed the coolant bled. Had a huge air pocket right before the thermostat but it runs perfect again now. ^_^
Just got a oil change after running it hot for a week or so.

 

I was gonna say, did you try purging the system? An air pocket in the heater core or some high point in the system can do that. I just had the same problem with my brother in laws altima. But it looks like you figured it out. The expensive way. At least you have a new water pump now.

 

Let me get this straight, these idiots didnt bleed the system after they changed the water pump??? Thats why I tell people to never take their car to the dealer unless they have a warantee.