Skip the auto shop - Our mechanics make house calls

Q: Heat

asked by on

Replaced radiator and thermostat due to over heating.fixed that problem but now the heat blows luke warm.used 50/50 antifreeze when filling it

My car has 165000 miles.
My car has an automatic transmission.

The most common reason for this after a repair is an air bubble in the system. Most of the time, if you completely warm the car, which means you have confirmed the thermostat is open by feeling the upper radiator hose it hot to the touch. If it is and the car isn’t overheating, take it for a test drive on the highway. Air bubbles can create overheating conditions, so do go to far. You only need to go about 45 mph for a few minutes. Once you get home, let the car cool for about an hour. Remove the radiator cap and see if coolant is all the way to the top of the radiator fill. If not, top it off and take a drive again.

This will often take a few tries to get the system to completely bleed. Sometimes I have had to run motors multiple times to get them to bleed the air bubbles from the system. The best test for a completely full cooling system is to check it first thing in the morning. This is when the cooling system will contract the most making room for more coolant.

If you determine the cooling system is full, but you still have luke warm air coming from the vents, the next thing to do is feel the heater hoses coming from the heater core at the fire wall. One should be really hot and the other should be cooler, but not significantly colder. If it is, you have a clogged heater. The easiest, thing to do at this point is flush the heater core. There are multiple ways to do this. Whatever way you choose, be sure to flush it both directions. If flushing doesn’t work, you will need to replace the heater core.

My information system doesn’t show there to be a heater control valve on your car, but I would still keep my eyes out for one. If it has one, make sure the valve is opening and closing.

I recommend the following inspection to help you should you need further assistance; Heater is not working replacement. Be sure to send the technician a note explaining your symptoms so he or she can come prepared.

Good luck!

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

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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: Hi Carlos my 2007 Dodge Durango got a leaking oil pan how much would charge to fix it?

Hi there. It depends on whether your leaking pan is caused by a broken oil pan gasket or the pan itself is cracked. If you plan on keeping your Durango for several years, you might want to be proactive and...

Q: Hesitation while accelerating and engine overheating on a '94 Toyota Corolla

The main problems this vehicle has for that problem are the spark plugs, distributor cap, and the wire set. On these older cars they are a one piece unit and just go bad. You will need to replace it. If...

Q: Temperature gauge arrow climbs high, then returns to normal

There is a cooling fan clutch mounted on the radiator, and this device will move air across the radiator to cool the liquid coolant inside. The water pump is responsible for getting the coolant where it needs to go. With...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...