Car Temperature Gauge Goes Up And Down While Driving? Here’s Why

When your car temperature gauge goes up and down while driving, it can be a sign of several different problems. The most common reason is that the thermostat isn’t opening fast enough to keep the engine cool. If this is the case, then there’s a chance that it could eventually damage your engine because it needs to run at a certain temperature in order to operate properly.

 In this post, I’ll be taking you through some other major reasons why your car temperature gauge would fluctuate while driving.

car temperature gauge goes up and down while driving

1. Cooling System Issues

If the temperature gauge is fluctuating, it could be due to a problem with your cooling system. Your radiator and water pump are the two main components that help regulate the temperature of your vehicle. If either of these malfunctions, your engine’s temperature can go as high as 245 degrees Fahrenheit and beyond. This would subsequently lead to serious damage to your engine.

Before you engage the services of a mechanic for further diagnosis and possible repairs, I recommend you check your coolant level to be sure it’s not a case of low coolant in your radiator.

2. Bad Fan Clutch

The fan clutch is a device that engages the fan to the engine. It’s an integral part of your cooling system, so any problem with its operation can throw off your engine temperature readings and make it difficult for you to determine what kind of trouble lies ahead for your vehicle.

If you believe something could be wrong with your cooling system but aren’t sure where to start diagnosing it, consider having someone come out and perform some basic tests on your car using specialized equipment.

This could include checking all aspects of the system in question (such as whether there is adequate pressure within lines) as well as measuring specific temperatures throughout various parts of the car’s engine compartment during operation time periods, etc.

3. Water Pump Issues

If the water pump isn’t working properly, this can cause your engine to overheat. A failing water pump may also result in a faulty temperature gauge reading, which will cause your car’s temperature gauge to go up and down as you drive.

4. Faulty Temperature Sensor

The temperature sensor helps to regulate the temperature of the coolant and detect any temperature issues with the car. If your car is overheating, then you should have this part replaced immediately. An overheating engine could cause serious damage to internal components and other important systems in your vehicle.

5. Leaking Coolant

Leaking coolant could be a result of a bad radiator or head gasket. The first step to take is to have your mechanic inspect the car to determine the cause of the leak and repair it. This should stop the fluctuations in your car temperature guage.

A cracked or broken radiator can cause hot coolant to leak out onto nearby parts causing them to overheat as well which can damage their functionality permanently or lead them to failure if left unattended long enough.

6. Bad Radiator

If you start to notice the temperature gauge moving up and down, this could be a sign that your radiator is bad. If the radiator is cracked or leaking, then it won’t be able to cool down your engine properly. That means that your car will overheat and cause damage to other parts of the engine.

Check the radiator cap for leakage by turning it off while driving and watching for any fluid seeping out of where it connects to your radiator hose. If you see any signs of leakage here, then there’s a good chance that your cap needs replacing. You can also check out these bad radiator symptoms to get familiar with things you should be looking out for before committing to any changes or repairs.

7. Head Gasket Blown

If the temperature gauge in your car goes up and down while driving, it could be a head gasket problem. When the engine’s coolant and oil fail to stay sealed from one another, they can mix together to form corrosive sludge that will eventually cause damage to your car’s engine.

Head gasket failure can also cause excessive heat, which makes it hard to maintain good fuel economy or even keep the car running at all (thus leading to overheating).

8. Stuck or Leaking Thermostat Valve

If the thermostat valve is stuck, it means that it is not opening and closing as it should. You’ll need to take your car to a mechanic so they can replace it for you.

If the thermostat valve is broken, then there will be no flow of coolant through your radiator and engine block. Your car’s temperature gauge may go up and down while driving because of this problem; if so, have your mechanic fix it right away.

A leaking thermostat valve can cause overheating problems with your engine when it should be running at normal temperatures—this could lead to an accident if you’re not careful.

Take care of any leaks by replacing parts or tightening them back up again after any repairs are made by a qualified professional mechanic who knows what he is doing.

How to Fix a Faulty Temperature Gauge That Keeps Going Up and Down While Driving

1. Check coolant level and sensors

If your car’s temperature gauge keeps going up and down, the first thing to do is to check your coolant level. If it’s low, add more to bring it up to the proper level.

Next, check your coolant temperature sensor by removing it and cleaning it with an electronics spray cleaner or rubbing alcohol on a paper towel.

Then remove your battery cable for five minutes and then reconnect it; this will reset the computer so that it can detect problems in your engine’s sensors.

If you do not have access to tools that can perform these tests yourself, take your car to an auto repair shop for professional assistance.

2. Replace The Defective Thermostat Valve

To find the thermostat valve, you’ll need to remove the air filter housing. The air filter housing is in front of the radiator and can be removed.

If your car isn’t overheating but the engine temperature gauge keeps going up and down, then this may be caused by a stuck thermostat valve. In this case, you should replace it before anything else happens to your engine. The replacement process is fairly easy and straightforward and can be done by anybody with some DIY experience:

Remove the old thermostat valve from the engine block using a socket wrench. Inspect the old thermostat for cracks or signs of leakage. Install a new thermostat into the engine block with the correct orientation.

3. Replace Faulty Coolant Temperature Sensor

The coolant temperature sensor can be found right next to several other sensors on top of your engine block.

Use a plier or spanner to remove any screws holding down the old sensor (be sure not to damage any nearby wires or hoses). Then disconnect any electrical connectors from underneath it before pulling out any clips that may be securing it into position as well.

Clean off any dirt or debris from around where you’ll be mounting your new part by spraying down its surrounding area with compressed air or wiping it down with paper towels dipped into rubbing alcohol, and then, replace all mounting hardware back onto their original positions using new screws if needed.

4. Eliminate Air in The Coolant System

If you’re experiencing a fluctuating temperature gauge, there’s a chance that air is getting into the coolant system. The easiest way to check for air in your car’s cooling system is by following these steps:

Take off the radiator cap and look inside. If you see any bubbles or steam rising from it, then there’s definitely air in your engine oil system.

To do this, remove the radiator cap and watch for bubbles. If there are any visible bubbles coming out of it, then you have air trapped in your cooling system and it needs to be eliminated before moving on to other possible causes for this problem.

Next, turn on your car and let it idle for about 10 minutes before checking again for bubbles or steam coming out of the radiator cap (you will likely need to add more coolant).

If you still see any signs of air in your cooling system after letting it run for several minutes, you might have to seek professional help as soon as possible.


If your car temperature gauge goes up and down while driving, it basically means that the temperature is unstable.

The first thing to do is ensure that the radiator cap isn’t leaking or damaged, this can also be caused by things like cooling system issues, bad fan clutch, water pump issues, leaking coolant, a bad radiator, stuck thermostat valve, blown head gasket, and a faulty temperature sensor.