CD7 Accord random temperature swings
 

since ive owned the car, the temp needle has always gone to a quarter of the way up the temperature gauge. on my last trip to my dads, (about a 2 hour drive), i noticed the needle would creep up about halfway on the temp gauge. it was a pretty cool day and the engine never got hot, just warmer than normal.
didnt seem to matter if i was going up a hill or putting it under a big load, but the needle would go back and forth from a quarter to a half. fans still kick on just fine. and when i checked the coolant level it was full.

anyone have any ideas as to why its doing this? im going to replace the water pump and thermostat as preventative maintenance, but i would think if either of those were bad it would overheat instead of just getting warm.

Re: CD7 Accord random temperature swings
 

old t stat. if ya swap it with a 200 you should be golden.

Re: CD7 Accord random temperature swings
 

Thermostat is a good guess, you may also have a problem with the coolant temp sender for the temp gauge. The temperature range for the gauge is very small, so even a mildly out-of-range temp sensor can cause false gauge readings. The sensor is usually pretty cheap, and you're going to be draining the coolant anyway, so replace the sensor while you're replacing the T-stat. Better yet, check the sensor at a known temperature with a ohm meter first (like with the tip submerged in boiling water, which is the 100degC temp reference and a known resistance); instructions are all over the internet.

A failed thermostat doesn't always fail closed (which causes overheating), thermostats can fail open or partially open also. This can cause the problem you're talking about where the temp only climbs to a quarter of the way up the gauge. The gauge says you're never getting up to temperature. But, it sounds like it's a very consistent temperature on the gauge, and I'm assuming that you've been through a lot of different load ranges and a lot of different ambient temperature ranges, and it's unlikely that thermostat failure can produce such a consistent temp reading under such a wide range of conditions. It would also make the engine warm up a lot slower in cold conditions, because coolant is always getting bypassed to the radiator if the T-stat is stuck partially open. Plus, in summer conditions the T-stat spends a lot of time open, so at some point the engine should reach full temperature if the T-stat is the problem. That's why I'm leaning toward the coolant temp sensor.