Can you fix a bad thermostat in a car?

Author: Ceasar Bruen  |  Last update: Tuesday, June 16, 2026

Just replace it. The chances of you opening it, replacing the right amount of the right paraffin, and sealing is are zero. BUT, the trick to getting it to work without air gaps keeping the hot water from opening it is to drill a 3 mm (⅛″) hole in it if the thermostat you bought does not have one.

Can I drive a car with a bad thermostat?

Driving a car with a broken thermostat is not advisable. The thermostat regulates the engine's temperature by controlling the flow of coolant. If it's stuck closed, the engine can overheat, leading to severe damage such as a blown head gasket or warped cylinder head.

How much does it cost to fix a car thermostat?

Car thermostat replacement time is 30 to 60 minutes, depending on the make of the car. It will cost you around $190 to $350, including labor. Thermostat repairs usually take more time, requiring extra time to diagnose and analyze the vehicle's thermostat. It can take up to 2 hours.

What are the symptoms of a bad thermostat?

What Are the Signs of a Bad or Broken Thermostat?
  • The AC or Furnace Won't Come On. ...
  • The HVAC System Won't Turn Off. ...
  • The Thermostat Is Unresponsive. ...
  • The HVAC System Short-Cycles. ...
  • The Room Temperature Doesn't Match the Thermostat Setting. ...
  • The Programmed Settings Reset Themselves. ...
  • Check and Adjust the Settings.

Can a thermostat be repaired?

Thermostats can malfunction or break but this is typically unusual. Many issues can be fixed with DIY thermostat repair. We'll detail some tasks you can do before thinking about hiring a professional.

Poor heat stuck open thermostat or clogged heater core? Heat works but not HOT

How to fix a bad thermostat in a car?

Thermostat Replacement: If the thermostat is indeed the culprit, it's time to replace it. Locate the thermostat housing (usually near the engine block), drain some coolant, remove the housing, and carefully replace the thermostat.

Is it worth replacing thermostat?

Replacing your thermostat offers several benefits, such as: Modern features: New thermostats often feature programmable options for different times of the day or week, allowing your system to automatically adjust when you're at work or school, arriving home, or asleep.

How do I know if my car needs a new thermostat?

5 Signs Your Thermostat Is Broken
  1. You Notice Erratic Temperature Changes. ...
  2. You Find Incorrect Readings on the Temperature Gauge. ...
  3. Your Vehicle Makes Concerning Noises. ...
  4. You Find Coolant Leaks. ...
  5. You Notice Problems with the Heating System.

Will you get a code if your thermostat is bad?

P0128 is an extension of OBD-II code P0 which indicates a problem with your car's coolant thermostat.

How to unstick a car thermostat?

This is an easy problem to solve yourself by simply removing the plastic outer casing and, with a very soft brush, delicately brushing off its coil and contact surfaces. It is most effective to clean the thermostat first at its lowest setting, then again at its highest setting.

What is the lifespan of a car thermostat?

A car thermostat is designed to last a long time – typically around 100,000 miles or 10 years. However, various factors can impact its lifespan. First, driving conditions play a role. If you regularly drive in hot weather or stop-and-go traffic, your thermostat may suffer additional stress.

Can I replace my thermostat myself?

In most cases, installing a new thermostat is a relatively simple do-it-yourself project that can result in improved comfort and convenience and one that can help you save energy.

What damages car thermostat?

Corrosion occurs, among other things if a wrong coolant is used. The corrosion attacks the thermostats aluminum parts that almost "etch away" (see figures 1 and 2). But also mixing of different coolants can cause corrosion. Therefore avoid mixing different types of coolant together.

Will a stuck thermostat throw a code?

A stuck thermostat will also trigger several indicators, warnings, and fault codes. As you read above, you'll first notice the blue low-temperature indicator that constantly stays on.

How to tell if your thermostat or water pump is bad?

Here are signs you've got a bad pump or thermostat.
  1. Corroded Cooling System Parts. Both of these cooling system parts can get corroded if they start to leak slowly. ...
  2. Leaking Engine Coolant. ...
  3. Erratic Temperature Changes. ...
  4. Poor Coolant Circulation. ...
  5. Overheating Constantly.

Can a bad thermostat cause AC not to work in a car?

If the thermostat is not working properly, it won't be able to regulate the temperature properly, which will cause warm air to be blown into your car. These are just some of the most common reasons why your car's AC might not be working properly.

How far can I drive with a bad thermostat?

The furthest you can drive an overheating car is about a ¼ mile before you risk irreversible engine damage. While some vehicles could still make it as far as 20 miles, we would never recommend driving very far with an overheating engine.

How much is a new thermostat for a car?

Generally, repairing a thermostat costs around $200 to $500. This is the price range you'll find for most vehicles, although some may be higher or lower depending on the circumstances. But if we're talking complete replacement, expect the price to increase by $50.

How can I test if my thermostat is bad?

7 Ways to Tell Your Thermostat Is Broken
  1. The Thermostat Has No Power. ...
  2. The AC or Furnace Won't Turn On. ...
  3. The Heater or AC Won't Turn Off. ...
  4. The Thermostat Reading Doesn't Match the Room Temperature. ...
  5. The Thermostat Doesn't Respond. ...
  6. The HVAC System Is Short Cycling. ...
  7. The Thermostat Forgets Programmed Settings.

How does a car act when the thermostat is bad?

Overheating is the most common symptom of a failing thermostat. Due to corrosion or aging, your car's thermostat can get stuck in a closed position. If this happens, the thermostat will not let the coolant reach the radiator, and, as mentioned above, the engine will overheat, causing severe damage.

How much does it cost to replace a thermostat?

The average cost of a new thermostat, including installation, ranges in price from $50 to $500 or more based on several factors including the type of thermostat, labor costs, the complexity of the installation, and more.

How to check if coolant is circulating?

Take your radiator cap off and note the coolant level. idle the vehicle until it's hot enough for the fans to kick on, maybe 10-15mins depending. When they do, you can look down in your radiator and see the coolant level drop and probably see it circulating as well.

How many hours does it take to replace a thermostat?

Installation typically takes about 1 hour.

How do you tell if your thermostat needs to be replaced?

Signs You Need a New Thermostat
  1. Heating or cooling system will not turn off or on.
  2. The temperature reading is incorrect.
  3. Recent spike in your energy bill.
  4. Frequent temperature fluctuations.
  5. Thermostat is 10 years old or older.

How often should a car thermostat be changed?

You may never need to worry about replacing your car's thermostat because they last 10 years on average. This being said, if you plan to keep your car for a long time, or if you drive an older automobile, there will come a time when you need to replace the thermostat.

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