How Long Can You Drive With Thermostat Stuck Open?


The thermostat in your car’s cooling system acts as a gatekeeper. When the engine reaches a high temperature, it’ll open to let coolant flow and prevent overheating. But when it’s too cool, the thermostat will stop the coolant flow instead. But can you drive with a thermostat stuck open, and if so, how long can you do that?

Yes, you can drive with a thermostat stuck open and do so indefinitely. That’s because a stuck-open thermostat will cause an overcooling condition that prevents the engine from running optimally. The engine won’t suffer immediate damage like if the thermostat was stuck closed. Still, it will experience excess wear and shorten components’ lifespans.

This guide will teach you everything you need to know about stuck thermostats. First, you’ll learn about driving with a stuck thermostat. Then you’ll discover symptoms to look out for and how you can fix their different root causes.

How Long Can You Drive With A Thermostat Stuck Open?

You can drive almost indefinitely despite having a thermostat that’s stuck open. That’s because the effects of it being stuck open dramatically differ from a stuck-closed thermostat.

A thermostat stuck in the closed position will prevent coolant from flowing through the vehicle’s cooling system. That will quickly lead to overheating, loud noises, burning parts, and catastrophic engine damage.

However, being stuck open only means that the coolant will flow even when it doesn’t need to. That will lead to overcooling, where the engine fails to reach its optimal temperature and doesn’t operate as efficiently as it should.

In other words, your car will still operate without suffering immediate damage when the thermostat is stuck open.

With that said, it’s a horrible idea to leave your thermostat that way and continue your daily driving habits. Engines experiencing an overcooling condition will not suffer immediate damage, but they will run inefficiently and experience excess wear.

You’ll shorten the engine’s lifespan if you continue driving with a stuck-open thermostat.

Besides that, having a thermostat stuck that way also prevents the heater from working. The source of that heater’s high temperatures is your engine’s heat. So, suppose the engine is running at a low temperature because of your stuck thermostat. In that case, you won’t have any heat inside the cabin either.

Read: Thermostat Stuck Open Symptoms

What Are The Signs Of A Thermostat Stuck Open?

Some of the problems you’re experiencing can mimic a thermostat that’s stuck open. So, you must know how to troubleshoot and determine if the thermostat is to blame.

Here are the short-term and long-term signs that your thermostat is stuck open:

  • The engine is always undercooled and keeps the cold engine indicator illuminated on your dashboard
  • The car produces more emissions out of its tailpipe due to inefficient fuel burning
  • The vehicle’s fuel consumption increases over an extended period

Components in and around your engine deteriorate faster with time

  • The car’s performance drops as it fails to produce power like before

You must understand the symptoms listed above. That’s because a thermostat can get stuck in closed and open positions, each with different consequences.

Read: How To Prevent Air Bubbles From Getting Into Your Car’s Cooling System

Why Does A Thermostat Get Stuck, And How Do You Fix It?

A thermostat gets stuck open for several reasons, some of which are preventable.

Here’s why your thermostat gets stuck, how you can fix it, and how you can prevent the problem from happening again:

1. Contaminated Fluid

First, your thermostat gets stuck in the open position because you have dirty or contaminated coolant running through your cooling system. Like every other fluid in your car, your coolant must be replaced regularly to ensure it stays clean.

Still, it’s important to remember that coolant can get contaminated even if you replace it on schedule. Dirt, debris, and other things can get mixed into the cooling system when you open the cap to pour fresh fluid into the reservoir.

When dirty coolant circulates throughout the radiator, it can cause buildups along parts like the thermostat. As that build-up becomes severe, it will prevent the thermostat from closing.

How to fix it: First, drain the contaminated fluid immediately. It’s also an excellent idea to flush your radiator out to ensure that any contaminants trapped inside are removed.

Then, pour fresh coolant into the reservoir and allow it to circulate.

Simultaneously, you’ll want to clean as much debris as possible from your thermostat. That should allow it to work usually, though you’ll need to buy a new one if it’s stuck permanently.

Read: What Happens When Your Car Overheats?

2. Failed Gaskets Or Seals

Remember that wherever there are fluids in your car, there are gaskets and seals to keep them contained. Unfortunately, those gaskets and seals wear out over an extended period and lose their ability to contain the fluid inside the system.

Even worse is that a failed gasket or seal can also cause external contaminants to infiltrate the cooling system, leading to the problem you read about in the previous section.

In that case, contaminated fluid is only a symptom, but the root cause is a failed gasket or seal.

How to fix it: You can’t service or restore failed gaskets or seals, nor would you want to. So the best solution here is to replace them with new ones, as they’ll last longer and give you more peace of mind.

You must flush the contaminated coolant and replace it with fresh fluids if necessary.

Read: Why Radiator Bubbling With Cap Off?

3. Old Thermostat With Weak Springs

A typical car thermostat will last approximately 10 years. Suppose your thermostat is around that age. In that case, the most likely reason it’s stuck is that its springs have become weak and cannot close the thermostat correctly.

How to fix it: There’s nothing you can do about an old thermostat, especially if its springs have gone bad. So, the only solution here is to replace the thermostat with a new one.

There are plenty of aftermarket thermostats you can buy on the market. Still, nothing beats an Original Equipment (OE) thermostat designed to work with your engine in particular.

4. Defective Thermostat

A thermostat can get stuck open even if you only purchased it recently. Assuming your radiator and coolant are in excellent condition, the likely cause is a manufacturing defect in the thermostat itself.

Manufacturing defects can happen even with the best spare part brands, and that’s why warranties matter when buying spare parts.

How to fix it: Whether it’s old or new, you must replace a defective thermostat with a new one. The only question is whether or not the warranty is still active.

If you’re still within the warranty period, get the seller or manufacturer to replace the thermostat with a new one. They’ll replace it for free if the defect is their fault.

Read: Why Radiator Fan Goes ON and OFF?

Final Thoughts

Overall, you must remember that an engine has an optimal temperature it must reach to operate efficiently. An engine that overheats will destroy itself, but one that’s too cold will run inefficiently and shorten its lifespan.

A thermostat stuck open will let coolant circulate too much, creating an overcooling condition. As a result, the engine won’t become hot enough to function correctly.

That can happen due to contaminated coolant, failed gaskets, seals, or old springs in the thermostat. The same problem can also occur to brand-new thermostats with manufacturing defects. In most cases, the best solution is to replace the thermostat with a new one that can open and close correctly.

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