I have a 92 Accord LX 4dr with 207k miles on it. The temperature gauge
started acting up recently. When I start the car the gauge immediately
goes to the top and just stays there until a few seconds after I turn
the car off. Then it slowly drops down to the bottom. The antifreeze
level is good and I made sure there are no bubbles in the system by
opening the bleed bolt until the coolant runs steady with no bubbles in
it. In fact if I turn the key to the accessory position the gauge will
max out before the car is even started. The car runs fine otherwise.

Any ideas what the problem might be? Bad gauge or bad sending unit?

Thanks