I have a 2002 Honda Odysee with 260,000 miles on it. It started randomly overheating this hot summer we have been having. We change the thermostat and flushed the coolant/radiator and still overheats. I do not see any leaking on the garage floor but am loosing coolant and need to put more in about every 14 days. I do a lot of highway driving. What should I look at next?
If you are losing coolant, but there is no apparent leak, then you have to think of the possibility of a breached head gasket.
Then, there is the question of cause and effect. Could the engine be losing coolant and overheating because of a breached head gasket, or did the head gasket become damaged as a result of overheating from another cause–such as a defective temperature sensor?
Taking things step by step, I would suggest that you first check the hose clamps to be sure that they are tight, and that you consider the possibility that there could be a pinhole-sized leak in a hose if it is over-aged. Look underneath the hood for evidence of dried-up coolant, which leaves a whitish residue.
If there is no evidence under the hood of seepage/leakage from hoses or loose hose clamps, then you should have your mechanic check to make sure that the radiator’s fans are running as they are supposed to, and do some tests for evidence of a bad head gasket.
Have you replaced the radiator cap?
If it’s not holding pressure strange things can happen.
I second the nomination for radiator cap.