I recently acquired a new Civic and of course, it needed work. When it ran thru a heat cycle the fan did not turn on and the bottom radiator hose did not get hot. seekerONE suggested: Replace Thermostat.

So I replace the thermostat and re run the car thru a heat cycle, the fan comes on, the bottom hose stays cold and the temperature gauge climbs.

Suggestions from friends were clogged radiator, bad sending unit, water pump, and air bubbles in the cooling system.

So seekerONE comes out that night with a great tool, a radiator cap connected to a funnel. Simple, handy, great way to start with the simplest thing that could be wrong.

First he checks the radiator for any corrosion or build up on the top blocking fluid from going down the tubes, things look good. The radiator looks new so that is good. He inspects the old thermostat that I took out and says, hmmm doesn’t look that old but you never know. Checks the water pump, the weep hole is dry. Checks my work that I did and says okay, lets start with the easiest theory, air bubbles.

He puts the device on the radiator, pours bottled purified water (I don’t need any more build up than I already cleaned up earlier that day) in and we start the engine. As it goes thru its heat cycle he repeatedly squeezes the upper hose moving any air bubbles that could be in the system. What do you know, we got a lot of bubbles.

Watching the water we see it begin to have a green tinge, which means the radiator fluid is now moving. Checking the hoses the bottom hose is now heating up.

The bubbles slow and the cycle goes as normal. We continue to let the car run through a couple of more heat cycles (meaning fan on/fan off). Temperature gauge doing well.

We then close everything up, take the car for a test ride and good news, temperature gauge normal.

I drove the car today, no problems. I never knew air bubbles/pockets could exist in a cooling system because I am still and always learning so I thought I would share this with those who may not know about it either.

Thanks seekerONE aka Steve for all of your help on this.

 

Happy to help...
it is always good to learn new things...just as long as you don't forget the old things

 

cooling system problems are cake. good job seekerone

 

kewl. This happens to Supras all the time. "Burping" our cooling is easy. Put the car on an inclinde (ass down) and turn the heater on. Not sure if this would work for the civic, but good post. Thanks for the info.

 

a little different from the Supra but the same (meaning i don't think we need to put the ass end down), seekerONE had the idea that if i had let it keep running thru heat cycles the way it was, over a period of time, it would have "Burped" itself. Guess cars like to act like babies sometimes

 

My radiator wasnt topped off one time, and it would say i was over heating sometimes while stopped. I just topped it off with purified water and I was good to go.