Car Temperature Gauge Rises Then Falls – What To Do?

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If you’ve noticed lately when driving that your temperature gauge is too hot or too cold, it can be an unnerving experience. Even worse when it keeps moving – rising and falling, like it can’t decide. What’s going on? Is your car going to overheat? We’ve checked with mechanics on just what you need to do when the car temperature gauge rises then falls.

There are several reasons that your car temperature gauge might be rising and falling. It’s worth noticing what situation this problem occurs in. For example, is your temperature normal when idling but hot when moving? Or only hot going uphill? These clues can tell you more. You should get a qualified mechanic to check your vehicle. Problems with your cooling system can cause overheating, which can cause damage to the engine. These possible problems include:

  • The thermostat is not working.
  • The coolant is low.
  • There is a blockage somewhere in the cooling system, and the coolant can’t effectively move.
  • The temperature sensor itself might be bad.
  • The water pump or radiator fan has failed.

There are even more possibilities, though these are some of the most common. This is why working with a qualified mechanic who can diagnose the issue correctly is so important.

Keep reading to learn more. This article explains why the temperature needs to stay in the middle of the gauge and what happens if it’s too hot (or too low). We also cover some of the different scenarios where you may notice an issue and what it indicates. Some tips included identifying a blockage in the cooling system and how to flush it out yourself. And finally, how to tell when the car isn’t overheating at all – it’s actually a faulty temperature sensor!

Coolant temperature gauge on a car's dashboard, Car Temperature Gauge Rises Then Falls - What To Do?

Should My Temperature Gauge Be In The Middle?

Most car experts agree that the temperature gauge should typically have the needle reading right in the middle. It can go up or down a little, of course. For example, if the AC is running, or you’re going uphill, then it’s normal for the gauge to reflect this.
 
But even then, the gauge shouldn’t be veering wildly and frequently from the middle. If it seems to be creeping higher than it ever has, that’s a cause for concern. It’s necessary to examine the situation closely and determine why before you end up with a costly repair bill.
The temperature gauge of a car

Why Does My Car Get Hot Going Uphill?

There are many reasons why your car might overheat going uphill. The simplest place to start is usually with your coolant. Check the levels and make sure everything is where it’s supposed to be. If the coolant is running low to begin, driving uphill can cause extra stress on the vehicle. Get help with checking your coolant level here.

If that’s not it, there are several possibilities still left. Your water pump or fan could be the issue. The radiator might also be clogged. You can always open the hood and make sure there’s no debris in the way, blocking airflow. 

One helpful tip is to turn on your heater. If your heater doesn’t produce heat but rather blows cold air, that indicates that coolant is somehow your issue.  It’s either too low or not flowing correctly. If it’s low, and you suspect a leak, get help with that here. If a blockage is the issue, try doing a flush like this one:

What Does It Mean If Your Car Is Dropping In Temperature?

You might think that, if overheating is so bad for cars, low temperatures can’t be a problem. But, while overheating can damage internal parts of the vehicle, running cold is bad, too. If the engine is too much below the ideal 200-degree Fahrenheit mark, it runs less efficiently and wastes a lot of gas.

If your car’s temperature is closer to normal when idling and drops when the car is moving, it’s most likely the thermostat. Sometimes, the thermostat can be stuck in the open position, affecting its performance. When working properly, the thermostat opens or closes on its own. This lets in as much (or as little) coolant as necessary to keep the perfect temperature.

What Are The Signs Of A Bad Temperature Sensor?

If you suspect that your coolant temperature sensor isn’t accurate, there are some indications to look out for. AAMCO Diagnostics Center lists several clues that can mean you have a bad temperature sensor.

First of all, if your temperature readings seem irregular, it’s always worth having a mechanic take a look. Similarly, if the car isn’t heating up as quickly as it used to, have it checked out. If there’s a genuine problem in the cooling system, you want to catch it as quickly as possible to avoid costly repairs. But, everything may be fine, and your temperature sensor gives faulty readings.

If your check engine or overheating light comes on, that can also be a reason to suspect that the sensor might be wrong. Again, it’s worth examining – if your dashboard warning lights are on for a reason, it needs to be fixed. And if they’re not, then your sensor needs to be fixed anyway.

The temperature sensor also helps guide just how much fuel is used by the engine. If a faulty sensor is sending too much fuel, you can see this in poor fuel mileage. You may also notice black smoke coming out of the exhaust – this extra, unneeded fuel ends up burned off as nothing more than smoke.

Smoking exhaust pipe of a car

Can You Drive With A Bad Temperature Sensor?

The coolant temperature sensor is necessary. Without it, the engine doesn’t get the right amount of fuel for the fuel-to-air ratio. If the fuel-to-air ratio is too heavy or too light, it can cause problems for your vehicle.

There might be too much fuel going through, which is a waste. Gas isn’t cheap, and burning it off for no reason because of a faulty sensor is no fun. If this occurs, you’ll notice a significant drop in your fuel economy.

Even worse, it can cause the engine to overheat. This eventually causes more damage to other internal parts of the engine. It can create knocking or misfiring in the engine. A temperature sensor is a vital tool. It’s one part of many serious calculations done to keep your car running perfectly. Without it, your car can’t work as it’s meant to. And, if you don’t take it seriously, it can ruin your engine altogether.

In Closing

If your car temperature gauge is rising and falling, it indicates a problem with the cooling system. The obvious place to start is checking your coolant levels. If that’s not the problem, look for signs of a blockage preventing the coolant from working properly. A heater that only blows cold air is one tell-tale sign. In this case, try flushing out the system.

It can also be a faulty temperature sensor, a stuck thermostat, a bad water pump or fan, or more. The cooling system of your vehicle is very complex and essential to good car performance. If it’s not working properly, it can affect your fuel economy. Even worse, it can cause your engine to overheat – and that can cause even more issues, like destroying the head gasket. If you can’t identify the issue easily, always have it checked by a qualified professional.

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