Two things are going on with my car. First, when I drive at freeway speeds and turn on the heater, the car temperature drops and then I hear the sound of a tea kettle going off. Second, I hear an off and on sound coming from under the hood on the passenger side. It sounds like metal scratching on metal or like a soft whistle sound. Thanks for all your help!
1997 Honda Accord LX
Is the thermostat more than 5 years old? If so replace it.
Flush the cooling system while you’re at it.
The sounds under the hood could be a belt or the water pump.
When was the last time the cooling system was serviced?
Make sure the cooling system is completely full and all air has been purged. There is a special bleed valve on the engine to allow the air to escape after filling the system.
Does your car have manual HVAC controls or “automatic climate control?”
Is your A/C being turned on by your heater selection? If so it would turn the denser fan on…and cool you down in the winter…and you would have that on and off sensation coming frm under the hood…do it again and look at your ac button…is it lit?