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Car Temperature Gauge High, But Not Overheating? 4 Reasons


Car Temperature Gauge High, But Not Overheating? 4 Reasons

Temperature gauges are far more common in older cars since in those days engine cooling systems weren’t nearly as effective as they are now. The purpose of the temperature gauge is, obviously, to show you the temperature of your engine at any given time. Sometimes, however, temperature gauges can give erroneous readings for one reason or another.

If your temperature gauge is reading abnormally high but your car isn’t actually overheating, there are a few reasons this might be happening. The gauge itself or the temperature sensor connected to the gauge may be broken, or there may be issues with some of the engine’s other components that are giving you a false reading.

In this article, we’ll be going over all of the reasons why your temperature gauge might be displaying a false high reading, as well as why your engine might be running hot but not overheating. We’ll also touch on what to do if your car is actually overheating, and share with you some other info about engine temperatures that you may want to know.

When we talk about a temperature gauge that is reading high even if the car isn’t overheating, then we’re talking about a couple of different scenarios. It could either be that your engine is running normally but the temperature reading is way off, or that the engine is actually running hotter than usual but not quite getting to the point of overheating.

We’ll be taking a look at a variety of problems that fit into both of these scenarios, so let’s get right into it. 

Faulty Temperature Sensor

Specifically, we’re referring to the coolant temperature sensor in this case. The coolant temperature sensor does exactly what the name suggests; it measures the temperature of the coolant and sends this information to the car’s computer, which helps the computer adjust things like the air/fuel ratio and the ignition timing.

Related: Why Does My Car Turn Off While Driving?

If the temperature sensor goes bad, it can potentially cause your temperature gauge to read high even if the actual coolant temperature isn’t that high. However, there are other symptoms of a faulty temperature sensor that are more serious.

temperature sensor location on engine

If the temperature sends a reading to the computer that is incorrectly high, the computer might adjust the air/fuel ratio to be much leaner than normal. Ironically, this can cause the engine to actually overheat.

So in this instance, the sensor isn’t triggered by high temperature; rather, the sensor causes the high temperature to begin with. 

Sometimes this sensor can act up if it becomes contaminated with dirt and debris. In this case, cleaning the sensor off may solve the problem. Otherwise, you’ll probably have to have the sensor replaced.

Broken Temperature Gauge

If your temperature gauge is displaying an incorrect reading, there’s a good chance that it’s the fault of the temperature gauge itself. It’s not super common for the gauge to break, but it certainly can happen.

Most of the time, your temperature gauge’s reading is going to be accurate, so it can sometimes be tough to determine whether your engine temperature really is getting too high or whether the temperature gauge is acting up.

You may have to check other components of your engine first to figure out how accurate your gauge is.

temperature gauge high reading

To that end, you should check the coolant levels in the engine, and compare the temperature between the engine head and the radiator hose. If the engine is hot but the radiator hose is relatively cool, that’s a hint. It could be a sign that the radiator is clogged or the water pump isn’t working.

coolant reservoir in engine compartment

You should also look for any coolant leaks anywhere around the engine. If you’ve determined that your engine is running normally, but the temperature gauge is still giving you a high reading, then it’s possible the temperature gauge is at fault. 

Bad Water Pump

The water pump in your car is actually slightly misnamed, since it’s technically the pump for the coolant. Regardless, the purpose of the water pump is to circulate cooling liquid through the engine.

coolant system diagram showing water pump location

If the water pump fails, the engine will start to heat up quickly when idling. However, you may also find that the temperature returns to normal once the car actually gets moving. This is likely because the extra airflow from the car moving is compensating for the lack of coolant circulation.

Related: How to Start a Car With a Bad Fuel Pump

If you’ve determined that your water pump is the problem, you should have it replaced as soon as you can.

A Clogged Radiator Will Cause Temperature Gauge To Read High

Another possible cause of a car temperature gauge reading high is a clogged radiator. Like a bad water pump, a clogged radiator will result in an engine that will heat up when idling, but cool off when the vehicle is moving at speed.

Pressure washing the radiator and transmission cooler

Your radiator may be clogged if it’s old and rusty. It can also become clogged if you are using old or poor quality coolant. Fortunately, if the damage isn’t too bad already, you may be able to solve the problem by flushing your cooling system and filling it up with new coolant.

If your car is actually overheating, you’ll want to address this issue as soon as you can. An overheating engine may sustain severe or possibly permanent damage, which will obviously mean a hefty repair bill for you.

When your car starts overheating, the first thing you should do is turn off the A/C (if applicable). Then, turn on the heat to full blast. Turning off the A/C reduces the load on the engine, which may help it cool down a little. Turning the heat on helps draw more heat away from the engine.

Next, you should find a safe place to pull over:

  • Shut your car off, and wait for your engine to cool down.
  • Wait at least 15 minutes for this while keeping an eye on the temperature gauge.
  • Don’t open your hood before the engine has cooled, as there’s the possibility of being burned by hot steam.
  • Once the engine has cooled, give your coolant levels a quick check and add some more, if you have it.
  • If the source of your problem is a mechanical failure, then you’ll need to repair it as soon as possible. An example of this would be a busted radiator fan or broken water pump.

If you can tow the car to a repair shop, you should probably do so at this point. But if towing is not an option, then you can still probably drive your car to wherever you need. This, of course, depends on how extreme your situation is.

Just keep an eye on your temperature and pull over to let the engine cool if the temperature gauge starts climbing again.

What Causes Overheating?

In general, an overheating engine is caused by the failure of some component of the engine’s cooling system. Cooling systems can fail in a number of ways, as we’ve discussed. The water pump can go bad or the radiator can become clogged. Furthermore, the radiator fan might be broken or there might be a coolant leak somewhere.

Temperature sensors can also cause overheating issues when they fail, as previously described. Your engine might also overheat due to low levels of engine oil, which will generate excessive friction within the engine. Also, a blown head gasket will allow too much air into the engine and cause it to run lean.

With all the different components of your car that can cause overheating issues, don’t feel bad if you aren’t able to figure out what the cause of your problem is. If you’re having trouble diagnosing the source of your overheating issues, a mechanic is only a phone call away.

What Are the Signs of an Overheating Engine?

Obviously, your temperature gauge should tell you if your engine is overheating. But, as we’ve discussed, warning systems can fail. There are other symptoms of an overheating engine that you should also be aware of. You should keep an eye out for the following if you suspect that your engine is overheating:

  • The car smells “hot”
  • Steam or smoke is coming from under your hood
  • The engine is making a ticking or thumping sound
  • You notice puddles of coolant under your vehicle
  • The engine’s power is reduced
  • The hood of the car is extremely hot to touch

Yes and no, depending on what exactly you’re asking. If you’re wondering whether it’s safe for you, personally, to be driving an overheating car, the answer is generally yes. The car won’t explode from overheating (although the radiator might, depending on the source of the problem).

On the other hand, if you’re wondering whether it’s safe for your car to drive it when it’s overheating, the answer is a resounding NO. If you drive for too long with an overheating engine, you risk several potential outcomes. Blowing your head gaskets or warping your cylinder heads are two possibilities. Both are considerably expensive repairs to perform.

If you suspect that your engine is running hot, you should take whatever measures you need to prevent it from overheating. Have the problem fixed as soon as you possibly can. 

If your car temperature gauge is reading high, though the car is not overheating, now you know what key things to check. A bad temperature sensor, faulty temperature gauge, broken water pump, or a clogged radiator can all be causes of this issue.

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