I have a 2005 Honda Civic EX. I bought the car brand new in 2005, so I am the only person who has owned this car. I have kept up all maintenance on my vehicle since purchase. I have never had any issues with my vehicle until recently. It started off overheating. I took my vehicle in for repair immediately. At that time I was told I had a leak in my radiator. I had the radiator replaced new. They also replaced the thermostat sensor. A month later my car started overheating again. I then had my thermostat replaced brand new and checked for air in the hoses. A few weeks later it overheated again. I took my car in again and this time the ran diagnostics on head gasket, water pump/timing belt. They said everything looked fine. They check fan to make sure its not getting stuck and assured me my fan was working fine too. They just topped my fluids off and sent me on my way. My car continues to overheat but only sometimes. It will work fine for weeks then one day it will overheat. Once I let my engine cool for at least 1 hour my car will be fine again for awhile. I just recently noticed that my heater is now not blowing heat out. My air conditioning works fine. My car hasn't overheated in a few weeks but my heater only blows cold air. It was suggested that I check my fan relays, which I just replaced. What else can be causing my car to only over heat once in awhile and causing my heater not to work?

 

Heater not working means there's a bubble of air in the top of the engine. Engine cold, take off the radiator cap and make sure it is full. If not, fill it up the radiator and idle the car with the cap off for a while-- add more if it drops down. While doing this the car should be parked on level ground or facing uphill and the heater dial should be on full hot.

If you keep getting a bubble of air like that, the head gasket is probably bad. A slow leak is harder to detect.

 

does it only blow cold when your stopped then blows hot again while driving if so it probably is air in the system. but how did the air get there maybe you have a faulty radiator cap or it could be the head gaskit which are notorious for failure on 01-05 civics.

 

It blows cold air only. No matter if I'm idled or driving. I was told that an air pocket could have gotten in when my radiator was replaced.

 

you can burp the system as mentioned above but i would recommend jacking up the front of the car.

 

Hi guys! I'm new here and I have had many different mechanics try to get thousands of dollars out of me for different diagnoses and I visited this site to try to get to the bottom of my issues and it looks like there are several '05 Hondas out there with the same issue as me. I will say though, that mine seems to have occurred in reverse and I wonder if that makes any difference. This will be my 3rd winter where my heater only blows hot air if I'm moving. When I idle the air turns cold. This past summer was the 1st time I noticed my temp gauge acting up. It was a very hot day and I was driving for about an hour on the highway with a little stop & go traffic from rush hour ... I was on a 2.5hr trip and I stopped halfway to cool it down and add fluid. After adding fluid it seemed to make it the rest of the trip without issues, but 2 days later on the trip home it overheated halfway back yet again. What would be your sequence of tests for this issue? Same sequence?

 

it could be just a bad radiator cap but definitely burp the system first. here watch this video