Q: Heat blows warm not hot

asked by on

The heat blows warm air but not hot. I assumed it was the heater core but after running the vehicle with the heat on I felt the inlet and outlet hoses to the heater core and both were hot. From my understanding this indicates that the heater core is functioning. I know my coolant system is in need of a flush but not sure if that is the only issue.

My car has 193000 miles.
My car has an automatic transmission.

You may have a clogged heater core that may be prohibiting the outer linings of the heater core to get hot. As you know, the heater core is a series of tubes that the coolant runs through that generates the heat from the warm coolant after circulating through the motor. These tubes can occasionally develop a buildup on the inner walls such that when the heater core is "flushed" this buildup on the inner walls of the lines remains and still allows the coolant to flow through the heater core. It is important to note that when the heater core is "flushed" it is possible to get good flow through the heater core while the inside walls of the heater core remain caked with buildup. As a result, the buildup on the inner walls prevents the temperature from rising to its capability due to the insulating effect of this buildup on the inner walls which will prevent the necessary heat transfer to properly heat the inside of the car. I would recommend having an expert from YourMechanic come to your location to diagnose and replace your heater core.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 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!
  1. Home
  2. Questions
  3. Heat blows warm not hot

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: Can i put a 2000 toyota celica GT automatic transmission in to a 2002 toyota celica GTS

The only way to be absolutely certain that it will fit, is to make sure that it's the same part number, and that the mounting points are in the correct place. That said, many people swap different transmissions into their...

Q: does the price quote include labor?

Yes, all prices generated when you use YourMechanic's "Get a Quote" function are complete and include parts and labor. There is a details tab on the quote page and if you click on "details" you will see the labor and...

Q: It will crank but will not turn on. Leaving a smell of gas

Hello, thank you for writing in. The vehicle may be having spark issues. If the spark is not strong enough to ignite all of the fuel, or does not ignite the fuel at all, the spark plugs may not be...

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...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.