Skip the auto shop - Our mechanics make house calls

Q: Temperature needles moves to "hot" when idle but goes back to "cold" when moving.

asked by on

Our temperature needle always goes to the red line when we are idle, only. If we are moving, it stays closer to the "c". If we stay idle and the needle goes to red the low coolant light comes on and keeps dinging until we move again. As soon as we move, the needle moves. There is never any smoke coming from the hood nor does it ever smell as if it's running hot. Also, our heat starts blowing cool air when idle. Today, the vehicle started shaking. Could all of these problem be related?

My car has 140000 miles.
My car has an automatic transmission.

A: The engine temperature fluctuating as it is...

The engine temperature fluctuating as it is can be caused by a number of components or problems. If the cooling system is restricted, coolant flow may be reduced at low engine speeds (idle) and be better when moving. If the cooling system has not been serviced for a long period, coolant passages in the radiator, heater, and engine may be restricted enough to limit coolant flow. Low coolant level can cause similar symptoms. Also, electrical issues can cause the vehicle to run hot at low speeds. If the radiator cooling fan is not turning on, the temperature will rise until you begin moving again, getting air flow through the radiator.

Have a certified technician diagnose the running hot issues as soon as possible. Running hot can cause performance issues as well as severe damage to the engine.

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

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: I need some idea of why my car won't start?

A no start diagnostic performed by a certified mechanic will give you a definitive diagnostic based on your specific circumstance but broadly what you should look for is the following. First, make sure the gas is fresh. If old, it...

Q: Our 2005 jaguar ran out of gas Now it won't start we added gas and turn the key on an off four times it sound like it will

When a car has a lot of miles on it, as yours does, running out of gas can damage the fuel pump. Most cars these days have the pump submerged in the fuel tank and the fuel passes through the...

Q: My windows keep fogging up and I have no idea why?

Claimed by Blake Griffin

Related articles

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.
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.