Skip the auto shop - Our mechanics make house calls

Q: only heast when driving cold when idle. heating core flushed twice. heat control valve and blend door seem to be working

asked by on

heat when drivig cold when idling. heater core flushed twice. temperature when driving 140-150 degrees then as idle it slowly goes down to blow cold air. heater control valve and blend door seem to be working

My car has 93500 miles.
My car has an automatic transmission.

The normal operating temperature for most automobile engines, including yours of course, is in a range of 185 to 220 degrees Fahrenheit. If your dash gauge is reporting a temperature as low as 140 degrees F, that likely means the car’s cooling system thermostat is stuck in the wide open position, thus preventing the engine from maintaining the desired temperature range. Not only will such cause very low temperature cabin heat but your fuel economy will be lower as well because the engine operates less efficiently if outside the design temperature range. As far as heater cores and radiators, if they are truly plugged, flushing is effective to varying degrees but, of course, just because you go through the "exercise" of flushing doesn’t mean the flushing has succeeded. Technically, you can flow test these parts after you have attempted to unplug them, but it is often more cost effective and more reliable to just simply change out the "damaged" component. Once a radiator is plugged up, it is usually has other problems as well. In fact, if you are really successful in flushing a radiator, you may dislodge the contaminants that are preventing it from leaking. At any rate, in your circumstance the best thing for you is to schedule a thermostat inspection/replacement during which the responding certified mechanic will go over everything and be sure that you do not have additional issues that are a cause of the no heat condition.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. only heast when driving cold when idle. heating core flushed twice. heat control valve and blend door seem to be working

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Screeching noise at low rpm possibly from intake manifold

It is possible that this noise could be coming from the internal parts of the engine. It is unlikely for an intake manifold to make noise as there are normally no moving parts associated with it. I would recommend checking...

Q: 1st and 2nd I lost 3rd and 4th actually goes into neutral in 3rd and 4th

I don't think it has to do with your speedometer. The speedometer cable that goes to your speedometer has a sensor on the opposite side but the sensor isn't big enough to cause damage to your transmission. I would check...

Q: Car battery dead but it turns on with cables but when I leave it off for 30 mins it dies

If you can restart the car after driving it but if vehicle sits for more than 30 minutes then will not crank the engine then you most likely have a bad battery due to dead cells inside the battery. Replace...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...