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Old 01-22-2008, 05:46 PM
Join Date: Jan 2008
Posts: 4
Default No heat at idle

For the past week my 2001 has no heat at idle. Works fine while moving. Coolent levels are fine, no coolent in cab and heats to operating temp. Anyone have any ideas what the problem is? I figured it may be the thermostat but the normal op temp is throwing me off.

Thanks in advance,

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Old 01-22-2008, 06:28 PM
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Default RE: No heat at idle

Does the interior fan work? Does the water valve open fully when you turn the **** on the dash to hot?

When the engine is warmed up and idling and the control on max hot and the fan on high, feel both hoses under the hood to the heater. If one is hot and one is cold there's likely a blockage in the core (assuming the valve is fully open). Disconnect the heater core and flush water backwards thru it to see if it is blocked and try to clear it.
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Old 01-23-2008, 10:47 AM
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Default RE: No heat at idle

Mk thanks for the response.

The interior fan works and the heat is hot as hell when moving. Its goes very cold when idling. I felt both radiator hoses and the upper hose is warm and the lower hose is hot. That tell you anything? I would like to flush the heater core however it is below zero here(that also never effected the heat).
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Old 01-24-2008, 02:15 PM
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Default RE: No heat at idle


Changed thermostat and flushed heater core. Still no heat while the car isnt moving. Anyone have any ideas?
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Old 01-24-2008, 02:25 PM
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Default RE: No heat at idle

If your car was older I might tend to think a water pump impellar was worn. 2001 though, doesn't sound like that should be it. Have you tried doing a really high idle while sitting parked to see if the airgets any warmer? If it starts to get warm doing the high idle, then it may be a water pump.

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Old 01-24-2008, 02:43 PM
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Default RE: No heat at idle

As mentioned by jim9418, if the water pump were the problem, wouldn't the engine temp rise above normal upon extended idling? This might be worth testing.

Also, have you looked into mk378's suggestion about the heater valve not fully opening? If not, the picture may help.

Click the image to open in full size.
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Old 01-28-2008, 04:56 PM
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Posts: 4
Default RE: No heat at idle

I guess I misunderstood mk, I will try that Ron, thank you.

Jim when I am in park and rev to even 2k it gives me heat. The water pump was changed @100k at 140k now. Still might be the problem. I did have it idling for over an hour and it didnt overheat.

I will try what Ron posted at let you know.

Thanks alot for the help!
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Old 01-29-2008, 09:03 AM
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Default RE: No heat at idle

After you rule out the valve and the core, the water pump is about the only other potential suspect. Do make sure that one heater hose is substantially colder than the other at idle with the heat on high. This proves that the lack of heat stems from insufficient water flow.

Water pumps usually last a very long time but if you have corrosive or abrasive stuff in the system they will get eaten up.
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Old 12-16-2009, 07:49 AM
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Thumbs up

I had this same problem with my 2004 Civic, and I found this site when researching what the problem could be. I took much of this info (above) to my mechanic and he said it probably wasn't the water pump because I had recently had my timing belt changed (the water pump was changed at that time).

The problem was the thermostat. He also noted, that in this situation it was crucial to use a Honda (factory) part, because he had done several thermostats in the past using a thermostat bought from a parts store, and the problem continued. Once he tried a Honda part, it worked perfectly.
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