Skip the auto shop - Our mechanics make house calls

Q: losse of heat when going 70.

asked by on

The heat works great up until around hitting 70mph, then it starts blowing cool air. The temp guage also drops. If you slow down, it goes back up and heat returns. Antifreeze is full.. Temp guage???

My car has 124000 miles.
My car has an automatic transmission.

Hi there. I have come across this same problem several times. The majority of the time it is caused by a failing thermostat. Due to the poor design of a metal thermostat molded into a plastic housing these will not wear the same and the thermostat ends up sticking in the housing and no longer closing correctly. If this occurs, the coolant does not stay in the engine long enough to get hot, and will get hot under an increased load, such as going up a hill. I would typically change the thermostat first. If you needed to have this done, consider YourMechanic, as a certified mechanic can come to your home or office to replace the thermostat for you.

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. losse of heat when going 70.

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: When I'm driving about 40 mph my Jeep Cherokee left wheel gets louder and when I turn left it makes a loud noise down there. What

Front end noises can be caused by a few different components. First, to eliminate the tires as a source, try rotating the tires. Solid axle 4WD vehicles can experience tire wear that can cause excessive noise. Run your hand across...

Q: 2006 Jeep Liberty passenger door won't open or close and interior light won't go off

Hi there. It is quite possible that the door's locking mechanism has broken or is frozen; which is typically the primary reason why a door won't open or close. This could be the lock actuator or the lock itself that...

Q: My car won't start and is completely silent.

Sometimes electrical components in the ignition cylinder can cause this type of problem; while in other cases, the starter, starter relay or ignition coil can be the reason why your Jeep is not starting. The best way to save time,...

Related articles

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...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
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...