My '91 accord sw ex overheats when ideling but as soon as the rpm goes over 2k the water temperature drops at normal level. I flushed and cleaned the radiator, checked the water pump. The thermostat works good. What could it be?

 

If you didn't replace the thermostat with a new Honda OEM part, do it now. It's the cheapest possible fix. If that doesn't work, you have bigger problems to take care of.

 

Dont know but you should check your sensors... worth a try.

 

did you bleed the system? it does sound like an indication problem. i would bleed it using the valve on top of the thermostat housing. you can rev the engine a bit while doing it, just watch out for the fluid coming up and get all the air out. if you have air in the system, it may cause the temp sensor to read incorrectly.