Q: My heater used to warm up when the engine warmed up, but now it takes far longer and never gets half as a hot as it used to.

asked by on

Is this my heater core? Or my thermostat? The engine itself seems to come up to the middle of the temperature gauge, and it never overheats.

My car has 170000 miles.
My car has a manual 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. My heater used to warm up when the engine warmed up, but now it takes far longer and never gets half as a hot as it used to.

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: Honda overheating

Hello there, a variety of faults that can cause your 2001 Honda Civic to overheat. Your vehicle has two cooling fans, one is for the AC, the other is for the radiator. When the engine reaches operating temperature both fans...

Q: Brakes squeak coming to a stop.

The front brake pads are squeaking from the metallic material in the pads when the pads were made at the factory are rubbing on the rotor surface causing the metal to metal squeal. If you do not like the noise...

Q: Burning smell from inside the cab?

Sounds like you have a handful of things to deal with. But as for the burning smell; if it is coming from the vents when the heat is on, it could be that you have a blower resistor overheating. The...

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...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
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...