Hi everyone, I am having a problem with getting heat at idle (650-800 RPM) even if I just came off the highway. It blows really hot at anything over 1000RPM.

I have changed the thermostat, flushed the coolant, and finally changed out the water pump. I changed the WP because it was overheating at idle with no heat in the cabin. Changing the WP helped it to stop overheating, eventhough I couldn't find anything wrong with it(bearing good, fins good etc.)

Is there a switch somewhere that is somehow controlled by RPM? I'm at a total loss here. Any help would be great, I'm freezing at red lights. Thanks

 

The only thing that I WOULD BEGIN to think that could be causing a problem would be that the radiator cap would not be holding sufficient pressure on the system at idle. But that would also cause the car not to warm up at an even, normal rate, so I DOUBT that would be the basis of your problem.

Inspect the hoses, and pressure test the heater core if you can. Those are really the only reasons I would suspect of the heating system not being sufficiently warm at a stop/idle.

And while you were in there.... I hope you changed out the timing belt when you did the water pump.

 

Seems to be a problem with this generation Civic . I have the same problem where there is no heat at idle but when driving the heat can take your skin off. On http://www.7thgencivic.com people say that a blown head gasket can cause this. Does the coolant get pushed into the reservoir?

 

Hi everyone, thanks for you input. Here's what Ive done so far.

1. changed out the WP & Belt ( this helped the overheating problem)
2. changed out the thermostat
3. had the heater core flushed.

After the flush I had heat at idle for 1 day and now it gone. I checked my oil, there's no coolant in it. Both hoses to and from the thermostat get warm (stat is working) The hose going into the heater core is warm, but is cold going out. So today I'm going to send some air back through the core to see what happens. I can't believe it's plugged up, I would think if it had dirt in it the radiator would too--It was clean, not one spec of anything.

I'll let you know what happens, thanks for all you help, If you can think of anything else please let me know.

 

Well, I took my car into Honda because after changing the thermostat, rad cap and purging the cooling system for air I have the same problems. No heat at idle and the coolant is boiling out of the reservoir. They took the engine apart and found that the head gasket was blown. Like my earlier post, this seems to be a problem with this car.