Hey guys,

My poor Civic is having a mysterious overheating issue. Whenever I drive on the highway for any amount of time and then slow down, the car overheats. It appears as if the coolant is going into the overflow reservoir, leaving the radiator empty. That would indicate a vacuum issue, right? However, there are no signs of leaks, no white smoke from exhaust, no milky oil, the fans are working properly, I've replaced the radiator, cap, thermostat, temperature reader for dashboard, and fan switch. Both the upper and lower radiator hoses are getting warm, though sometimes when I turn on the heat, it takes a few minutes for hot air to blow out.

I'm really at a loss! The mechanics I'm taking it to are scratching their heads, too. Can anyone offer suggestions??

 

Causes of an Overheating Car:

Overheating can seriously damage a car's engine if left unchecked. Although overheating simply means that a car's engine temperature exceeds normal operating temperatures, the causes of overheating are varied. What follows is a brief list of some of the most common causes of engine overheating.


Faulty Radiator

Faulty Water Pump

Coolant System Leaks

Faulty Thermostat

Low Engine Oil Level

 

I agree with Gilbert and he has very efficiently pointed out most aspects which are responsible for a faulty cooling system. You could check the complete plumbing too which could be clogged somewhere, restricting coolant flow properly. You may also need to take apart (or just disassemble) the radiator and give it as thorough inspection as well.