Your engine isn’t supposed to run hot—but it’s also not meant to run cold. If you’ve noticed that your temperature gauge barely moves off the bottom or your heat isn’t working as it should, your engine might not be reaching normal operating temperature. And while it may not seem like a major issue, a car that runs too cool can cause long-term problems, especially in fuel economy, emissions, and engine wear.
So what causes this, and what should you do if it happens?
The Thermostat Could Be Stuck Open
One of the most common reasons a car runs cold is a stuck-open thermostat. The thermostat controls how much coolant flows through the engine. When the engine is cold, the thermostat stays closed to help the engine warm up quickly. Once it hits the ideal operating temperature, the thermostat opens to let coolant flow and keep the engine from overheating.
But if it gets stuck open, coolant flows too soon and too freely, keeping the engine from ever warming up fully. This means longer warm-up times, lukewarm air from your vents, and reduced performance. Replacing the thermostat is a relatively simple fix, and it can restore proper temperature regulation.
Coolant Temperature Sensor Issues
Another possibility is a faulty coolant temperature sensor, which tells your engine control module (ECM) how hot the engine is. If this sensor sends inaccurate readings, the ECM may adjust the fuel mixture incorrectly—often resulting in a rich fuel mixture, which burns more gas and reduces efficiency.
In many cases, a bad sensor can also affect the behavior of your temperature gauge. So, if your engine feels normal but the needle never moves, it could be an electrical or sensor-related problem, not the actual temperature.
Outside Temperature Can Make It Worse
In colder climates, the symptoms of a low engine temperature are even more noticeable. During winter in San Francisco, CA, for example, if your car already has a weak thermostat or minor cooling issue, cold air from outside will make it much harder for your engine to reach and maintain its ideal operating temperature.
Even if the problem isn’t noticeable in summer, it might suddenly become obvious when the weather drops. That’s why it’s important to pay attention to the symptoms and not assume your car is “just fine” because it’s running cool.
The Effects of Running Too Cold
It may not feel urgent, but consistently running below operating temperature can quietly cause excess fuel consumption, carbon buildup in the engine, and increased emissions. The engine never gets hot enough to burn off fuel residue efficiently, leading to dirty spark plugs, reduced power, and sluggish performance.
You might also notice that your defroster or heater doesn’t work very well. That’s because the heat inside your cabin relies on hot engine coolant flowing through the heater core. If the engine never warms up properly, neither will the interior of your car.
How to Know It’s Time for a Check-Up
If your temperature gauge is always low, your heat is weak, or your gas mileage seems worse than usual, it’s a good idea to have your cooling system inspected. Even if your engine light isn’t on, that doesn’t mean everything’s working as it should.
A simple thermostat replacement or sensor fix can solve the issue before it begins affecting your engine in more serious ways.
Is your car running colder than it should? Let the experienced team at Taylormade Automotive in San Francisco, CA, diagnose the issue and get your engine back to peak efficiency. From thermostats to sensors and everything in between, we’ll make sure your vehicle stays in its ideal temperature range.