Intermittent Heat

CivicZ4 · 10-07-2009

I have a 1999 Civic DX. I am having an issue with the heater. There is no heat when I turn the heater on, the blower fan is working.

I replaced the thermostat assembly. Now when the heater is turned on, there is heat but constant interruptions with cold air. I heard this might be caused by air bubbles in the coolant (or not).

Any recommendations?

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gearbox · 10-07-2009

yeah you need to bleed the system. when the car is cold, take off the radiator cap and start the car. warm it up to operating temp by revving to 3k rpms. turn the heater on full blast and keep the coolant level to the top. watch as bubbles start coming out. once it looks like theyre gone, put the cap back on.

CivicZ4 · 10-07-2009

Okay, I'm new to this.

So after I refill the coolant, and the car is cool, I take of the radiator cap, start and warm up by revving.

Where am I watching for the bubbles to come out?

gearbox · 10-07-2009

out where the radiator cap was. thats the point of taking the cap off so you can see the bubbles. you need to keep adding coolant to keep it full if it drops down.

CivicZ4 · 10-16-2009

Didn't work. When should I think about replacing the heater core, and how difficult is this?

gearbox · 10-16-2009

very difficult. its behind the dash and little room to work with. all day project.