My Honda maintains normal temperature when on level highway. Climbing to 3000 feet (from about sea level) overheats to the red. It has a new radiator. After the first time I removed the thermostat. It does not lose liquid. After reaching 3000 feet and on level run it returns to normal. There are no leaks around the water pump. What should I try next?
Thank you.
How many miles on this car? Does the electric fan come on when it’s supposed to? To see, turn on the AC & the fan should run.
How old is the water pump?
Removing the thermostat is NOT a good idea. Please put the thermostat back in.
If the cooling fans are working correctly I’d wonder about the head gasket, but make sure the fans are working first.
I hope you put the thermostat back in.
Any symptoms besides the gauge?
You may want to invest in an infrared thermometer.
This is a classic symptom for a radiator cap that is not holding the specified pressure. Try a new cap. If one came with your new radiator, it could be defective or the wrong pressure.