Heat when not moving...

[Ryan Singh]

So I have a question...it's not DSM related but I think it would probably be the same as any other car.

If you're driving with the heat on, and the car stays warm up until you stop at a red light...then begins to blow cooler air; is that a heater core issue?

Oh btw, it's an 03 Civic that's doing this.

Thanks

[Greg Durban]

Check your coolant level first. That's usually a tell tale sign. And if it turns out to be low you need to find out where it's going.

Does the temp gauge  go up when your just sitting there? If so could also be a thermostat (sinple fix).

[John Hartman]

plus one for Greg.

I would suggest possibly its the water pump if its not just low on coolant or a tstat.

If the engine is spinning at cruise rpm(3000 or so) and its fine, then at idle(800 or so) the water pump is possibly not keeping up?  If the impeller fins are worn or pitting etc, or even loose on the shaft, it won't move much water at low rpm but might be able to get some moving at higher rpm.

[Jason Harwood]

Could also be a BHG.

[Ryan Singh]

Sweet, thanks guys. I'll keep you informed.