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.

A: Hi there. I have come across this same prob...

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.

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・Save up to 30%

Get a quote

What others are asking

Q: I have a jeep Cherokee 89 and I replace the transmission lines but the new ones won't fit into the transmission the right clips ar

During different years the transmission lines had different types of ends that go into the radiator. If you have just nipples on the lines, then get the proper adapters from the parts store to match them and they will screw...

Q: Convertible stop not closing.

Hi. The system for the convertible top has a motor which requires power. The electrical circuits must be checked as well as the motor for faults. Have a technician check for binding in the convertible top assembly and check for...

Q: Bubbling in coolant overflow tank

Seems to me like you just answered your own question. The coolant bleeder is stuck. If you cannot get the coolant bleeder unstuck then you should see bubbles in the overflow bottle for up to a week to completely get...

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 to Renew Your Car Registration in Oklahoma(DELETED)
Having your car registered with the Oklahoma Tax Commission is an important part of driving legally in this state. You will need to do this within 30 days of moving to Oklahoma...
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...