Why Car Temperature Gauge Goes Up And Down While Driving

Why Car Temperature Gauge Goes Up And Down While Driving


April 5, 2022

While traveling, it’s critical to keep an eye on the temperature gauge, particularly if you’re stopped in traffic or climbing a hill. You’ve arrived at the correct location if you’re interested in why the car temperature gauge goes up and down while driving.

In addition, we’ll go over how the temperature gauge works as well as what you can do to avoid your automobile from injury by overheating.

When the engine is cold, it shows a lower temperature reading because its components are taking longer to reach operating temperatures.

When the automobile is equipped with an automatic transmission, apply light pressure just after shifting from Park into Drive and releasing your foot from the brake as if you’re applying the brakes.

What Is The Temperature Gauge And How Does It Work?

Why Car Temperature Gauge Goes Up And Down While Driving

The temperature gauge shows you the engine’s operating conditions. It’s one of the most important instruments in an automobile with an inner combustion engine, after the speedometer.

The coolant’s temperature is measured on a gauge, allowing you to take action before damage is done to the engine. The water pump transports the coolant throughout the system, which is warmed by the engine and chilled by the radiator.

The thermostat controls the temperature and activates the radiator fan if necessary. The coolant temperature detector is positioned near the thermostat and transmits an electric signal, which is then transformed into a gauge lesson.

That shows the car temperature gauge goes up and down while driving.

What Is the Temperature Gauge’s Purpose?

It’s critical to understand what the standard temperature gauge motion range is. When the engine is frigid, since the minimal reading is generally set to 122 degrees Fahrenheit, the temperature gauge begins at the bottom.

When you turn on your automobile’s engine, it generates a significant amount of heat and the car temperature gauge goes up and down while driving.

In order to balance out the temperature differences according to physical thermodynamics principles, the heat from the engine is transferred to the coolant.

The needle on the gauge rises until the engine reaches its optimal operating temperature, which is generally between 180 and 220 degrees Fahrenheit. Almost every automobile’s thermometer has a particular range to indicate the optimum temperature.

When you swap the ignition off, the internal combustion engine will shut down and the coolant will cease flowing. The coolant temperature detector is near the thermostat, which means it will quickly lower in temperature as a result of trapped coolant inside the engine.

The temperature measurements given are typical for a mechanically sound vehicle that is driven to the fullest of its capabilities. There may be numerous reasons behind the car temperature gauge goes up and down while driving, which we’ll discuss in further parts of this article.

How Do Thermostats Work?

Why Car Temperature Gauge Goes Up And Down While Driving

The thermostat is a valve that connects the engine to the radiator and is used to regulate temperature. The thermostat is temperature-sensitive, expanding when exposed to heat and contracting when cold in order to minimize circulation.

Synthetic wax, which serves as a shrink and expands agent, is a clever mechanism that employs synthetic wax as an expansion agent.

The Temperature Gauge Is Rising Too Fast

The car temperature gauge goes up and down while driving for two reasons. The first is that you’re driving uphill incorrectly, and the second is a problem with the coolant system.

Uphills And Downhills

The strain on the engine is greater when you’re driving up a hill. It must not only strengthen the wheels and force the automobile ahead, but it must also overcome the slope.

Keep in mind how taxing lengthy flights of stairs or cycling uphill can be; when you’re driving up a hill, your engine goes through similar motions to those experienced while climbing

One of my driving instructor’s most basic instructions has been how to climb hills. To increase the RPM, maintain a lower gear and drive at 3,000 RPM or half the distance between zero and redline in most cars with a manual gearbox.

The same rules apply to automobiles with automatic transmissions, except you must move the gearbox into the “3,” “2,” or “L” positions to prevent it from moving up. We’ve discussed this in greater detail in a post called What Does “L” Mean on a Car’s Gear Shift?

Going too fast doesn’t imply you should push the RPM – the gear ratio will prevent this. You’re pushing the water pump to cycle coolant faster and avoid overloading.

Because of increased RPM, the engine produces more power, allowing it to transport greater weights with ease that’s the reason why the car temperature gauge goes up and down while driving.

Scarcity Of Coolant

Why Car Temperature Gauge Goes Up And Down While Driving

Remove the cap from the coolant bottle and lift up the hood to reveal a white plastic container with a steam warning label on it. On both sides, there are temperature restrictions as well as neatness notes.

There are also coolant marks on both sides, including a maximum and minimum gauge and indicators for when you’re not running it on water.

If the minimum level has dropped below the cap, add more coolant. It is not advisable to mix antifreeze colors, but different manufacturers can be combined. If you wish to put water, use distilled water since it is free of particles.

The Steam Alarm Has A Cause

The coolant is pressurized and creates a white cloud of smoke and searing-hot water, which can induce severe burns.

After the engine has completely cooled, keep the coolant cap shut until you’re confident it’s completely cold. Even then, as a precaution, cover the top with a towel. We’ve covered the time you should stay for the engine to cool already.

Water has a higher freezing and boiling point than antifreeze. Water offers a relatively small margin of safety before it surpasses the restriction when compared to antifreeze.

Because most vehicles run at temperatures between 180 and 220 degrees Fahrenheit, water will only offer a minor level of protection before overheating.

When the weather is freezing, it becomes considerably more critical. When water freezes, it expands and grows powerful enough to blast pipes, break the water pump, and perhaps damage the engine block.

Because of this, a 50/50 combination of purified water, then antifreeze are advised. If you want to count more coolant while going on the road, use water instead; but be sure the coolant’s tolerance to high temperatures is sufficient before winter with an antifreeze tester.

Now it has become clear how the car temperature gauge goes up and down while driving.

Dying Water Pump

The water pump is in charge of circulating the cooling system’s coolant. Because the coolant can’t be dispersed out from the engine, it will rapidly heat up when it breaks.

Coolant leaks and blubbering noises arriving out of the pump are indications of a failure, although a more significant break would result in an immediate rise in temperature gauge reading.

Flawed Radiator

Why Car Temperature Gauge Goes Up And Down While Driving

The function of the radiator is to cool down the coolant so that it may be reused in a subsequent process through the engine.

A blocked, rusted, or leaking radiator might result in an increase in temperature, so inspect it carefully before deciding if it must be repaired or serviced.

The Temperature Gauge Refuses To Increase

During the winter, when the car temperature gauge goes up and down while driving, it might take longer for the temperature gauge to return to normal. If it doesn’t seem like it’ll recover at all, there’s an issue with the thermostat.

It’s possible that the cap has seized open and failed, allowing coolant to flow despite not achieving the required temperature. Driving with an engine that is too freezing can cause other problems and malfunctions, so change the thermostat as soon as possible.

While driving, the temperature gauge rises and falls. The gauge may fluctuate while you’re driving, although it’s exceptionally unusual. While four distinct causes have been attributed to the gauge fluctuating while driving, none of them is correct.

  1. Flawed thermostat.
  2. The coolant temperature sensor (CTS) is faulty.
  3. A yielding temperature gauge.
  4. Troubles with the vehicle’s electronic control unit (ECU).

Poor Thermostat

Why Car Temperature Gauge Goes Up And Down While Driving

The thermostat is designed to adjust in form as the coolant temperature fluctuates. The movement is self-regulating, and if the thermostat is functioning correctly, the coolant will gradually reach a chosen temperature.

The water-cooled thermostat might open and shut the valve too quickly before it fails completely, causing the coolant temperature to vary as it is unable to settle.

The fluctuating temperature gauge indicates that the coolant temperature is correctly shown on the thermometer, so the car temperature gauge goes up and down while driving.

The Coolant Temperature Sensor Is Faulty.

The coolant temperature sensor (CTS), is sometimes known as the engine coolant temperature sensor (ECTS). The CTS resistance varies with temperature, receiving a steady voltage from the electronic control unit (ECU).

The resistance sends ECU data on the coolant temperature to the temperature gauge, which is then displayed. If there’s a problem with the CTS, it won’t give reliable information, compelling the temperature gauge to fluctuate erratically.

Flunking Temperature Gauge

It’s strange to be overly sensitive, since when the temperature gauge swings like a chess metronome or pendulum, it’s apparent that something is wrong with the gauge. It can also be the ECU.

The Electronic Control Unit Has Issues

If the ECU begins to break down, you may expect a slew of problems before you even notice the temperature gauge.

It might prevent you from driving your car because it is in control of almost all electronic systems. This is a significant issue, and you’ll want to get expert assistance in diagnosing and fixing it.

How To Change A Thermostat That Is No Longer Working?

Why Car Temperature Gauge Goes Up And Down While Driving

Replacing a thermostat is both time-consuming and expensive. Replacing a thermostat costs anything from $100 to $300, which makes doing it yourself a significant money saver.

A funnel with a bucket, a filter, a flathead screwdriver, and a hose clasp are all you’ll need.

How To Substitute A Thermostat

  1. Turn the ignition to the “on” position. Locate the thermostat housing. It may be near the engine or within one of the bottom radiator hoses. Find out where your car is located using Google.
  2. Place a pail beneath the thermostat as the clamp will release some of the coolants.
  3. Remove the hose from the clamp by loosening it with a flathead screwdriver.
  4. Remove the thermostat housing from the engine and drain the coolant. Examine the old and new thermostats to see whether they’re the same.
  5. If they’re the same size, replace the new one in place. In case of a mismatch, simply change the ancient hose clamp.
  6. Remove the hose from the housing and compress the clamp.
  7. You’ll need help with this stage, as you must separate the drained liquid and return it to the coolant bottle.
  8. Inspect the coolant levels and count more if required.

It’s as easy as unscrewing one screw and then swiveling the fan blade. Depending on how good a mechanic is, it might take 10-15 minutes to finish.

How To Supersede A Failed Coolant Temperature Sensor

It’s as simple as unscrewing one bolt and replacing it with another to change the coolant temperature sensor.

Take a look at the list of supplies you’ll need to finish the job once we get into the stages. But first, take a look at the list on which you’ll need to rely in order to accomplish it.

How To Change The Coolant Temperature Sensor In Your Vehicle

  1. Locate the sensor, which is typically near the thermostat. It’s easier to figure out where it is using Google.
  2. Place the bucket beneath the sensor.
  3. Remove the old sensor from its connector pin. Examine the connector slots on both sensors to see whether they are the same.
  4. Remove the old sensor using the ratchet, extension, and socket. As soon as you’ve unscrewed it, work fast to prevent coolant from leaking out of the hole.
  5. Remove the old sensor by hand, then fix it in place with the socket once you’ve installed the new one.
  6. Put the connector pin back on.
  7. Examine the reservoir’s coolant levels. If there’s a lot of coolant in the pail, use the funnel to drain and replace it in the system.

If you know where everything is, you can do this task in less than 2 minutes. Even though you may lose some coolant, you may test it and set it back into the system if you take your time.


How To Supersede A Failed Coolant Temperature Sensor

Why The Car Temperature Gauge Goes Up And Down While Driving?

If your car temperature gauge goes up and down while driving, as a result of acceleration, you should get your vehicle examined to discover the source.

Even if you drive aggressively, coolant levels should not fluctuate significantly, so modest acceleration shouldn’t cause significant increases in the temperature.

If you’re revving while driving on a chilly engine, though. Because the engine must be cooled as quickly as possible to attain its optimal operating temperature, it will not be chilled as efficiently when you accelerate.

Never put your foot on the accelerator before it has reached the desired temperature; otherwise, you risk harming your car.

Is It Typical For The Coolant Temperature To Vary?

The temperature varies depending on the sensor’s sensitivity and measuring frequency. The cooling system temperature is continually adjusted, but if the temperature gauge offered real-time data, you would be too distracted by looking at it.

Unless you’re driving uphill or there’s a problem with the radiator system, most gauges will remain in place at the proper operating temperature. You won’t notice any movement unless you’re driving uphill or the engine is too cool

What Are The Indicators That Your Thermostat Is Faulty?

There are several symptoms to look for, including a higher or reduced than normal temperature reading, leaking coolant, engine problem, and abnormal vibrations in the engine compartment. It become easy to judge now why your car temperature gauge goes up and down while driving.


The unstable temperature gauge is not a reliable sign., but the majority of the reasons are inexpensive and straightforward to repair.

I’ve listed all of the reasons for an erratic temperature gauge and how to fix them as well as any other details you should know in this post. If anything new has been discovered, I strongly advise that you read on.


Jeffrey Bryce is an experienced motorcycle rider with years of experience caring for motorcycles. His natural fondness for motorcycles have made him come up with LetsGoForARide.com, which is dedicated to answering and teaching you how to care for your bike with the care it requires. LetsGoForARide is the one of his important lifework in reaching out to communities of motorcycle enthusiasts on how to take care of their bike and choosing the correct spare part.