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2002 honda civic heater gets cold

My wife drives a 2002 civic (mostly around town). when the car is at running temp.with the heater on and she gets top a stop sign or red traffic light, the heater starts to blow out cold/colder air. We took the car to a dealer and asked them to flush/fill the radiator and fix the problem. Well they flushed/filled the radiator and said “Yup, it still does it. Would you like us to diagnose the problem more for a minimum of 1 hour labor cost?” What could be the problem with the reduction in heat?

You most likely have an air bubble in the coolant system…that civic SHOUD have a bleed nipple on the thermostat housing to “burp” the air bubbles out of the system.

It can also be caused by a faulty thermostat…cheap to replace…
A clogged radiator can also to this…or a clogged Heater core…of a faulty heater valve…can you ascertain if the heater Hot/Cold…controller is actually working the heater valve properly…at some point they made this control electric instead of using a cable operated valve…all good things to check.

I would check for air bubbles first…then the valve operation…then the thermostat…then move on to bigger items…see how you make out with the first few suggestions before moving on…

Did you ask them to flush/fill the radiator, or did you ask them to fix the heater problem?

You didn’t say the engine temperature is abnormal, so I’m going to assume that’s OK. I’m also going to assume the dealer correctly bled all the air out of the cooling system when he refilled the coolant.

Did they, by chance, install a new thermostat when they flushed and refilled the cooling system?

If the heater core is getting hot, which you haven’t verified yet, the problem would be in the HVAC system under the dashboard. Most likely the control for the blend door, which controls interior temperature.

Which is it? Cold, or coldER air?

If it’s just colder air, how cold is the weather? All cars will do that if it gets cold enough because the engine doesn’t produce enough heat to keep the coolant hot, which means the heater doesn’t have hot water to get heat from.

Worn out water pump could be one guess. Not enough coolant circulation at low rpm. Does the temp creep up at idle?

I was going to say a water pump, but have decided that the only ways water pumps fail is they either leak…or the bearings fail…or the impeller falls off or there is some type of pump body damage causing it to leak…

If the impeller is still attached to the shaft the water pump has NO CHOICE but to function…DO YOU GUYS AGREE WITH ME HERE? I have seen people change water pumps and install new ones saying to me …WHOO HOO That was definitely the problem… and when I look at the old pump the impeller is still attached…and I say…you didnt fix anything…and was right…everytime.

Pumps cant be “bad” if the impeller is turning, no leaks, no bearing issues, no holes or other sillyness…RIGHT?! I still have an argument running w/my buddies…

I have seen a water pump that had the impeller still attached, but most of the vanes on the impeller mostly worn or corroded away. In this case, the water pump did still pump some water, just not enough water. It can happen, depending on what the impeller is made out of.

Well OK…thats understandable and is akin to the impeller falling off type of failure…so OK…perhaps they have reduced flow due to a deteriorated impeller but that HAS to be rare…I’ve never seen an eroded impeller before. If this were the case they would have issues with the engine temp dont you think?

It’s Anybody’s Guess. I Don’t Know If All The Chronology And Elapsed Time Is Correct In The Story, But I’m Going To Vote For A Failed Head Gasket. The Dealer Was Correct. Proper Diagnosis Is Required.

If people with car in front of them can’t pinpoint the problem then nobody here can, either. Get a proper diagnosis.


Yes, I would think it would lead to the engine overheating, and yes, it should be very rare. I’ve only seen one, and clearly the owner had not changed the coolant in many years.

Yeah we are severely limited in diagnosic powers via the internet…many times I can hear and smell a problem…quite literally, if the car is in front of me in person.

Its like someone saying that “I am losing coolant and have no idea where its going” on the internet…and asks for help… but forgets to tell us about the Cumulo-Nimbus cloud of Steam rising from their tail pipe…“Oh I didnt think to mention that”…LOL We would spot that in a millisecond and know whats up…