How to Replace a Coolant Temperature Sensor

Updated on October 23, 2016
Coolant temperature sensor.
Coolant temperature sensor. | Source

A bad coolant temperature sensor (CTS or ECT--engine coolant temperature sensor) can seriously disrupt the fuel system and engine operation of your car.

That's because the ECT sensor tells the Electronic Control Module (ECM-your car computer) at what temperature the engine is operating, so the computer can make some important decisions. For example:

  • how much fuel the engine needs
  • when to go into closed loop operation (to monitor and adjust engine operation)
  • whether to advance or retard the spark (for best ignition system operation)
  • and make other adjustments for optimal engine performance

As you can see, a bad CTS can really mess up engine performance:

  • A permanently closed (electrically shorted) coolant sensor will cause an increase in fuel consumption and potential damage to the catalytic converter.
  • A permanently open (broken circuit) coolant sensor will starve the engine of fuel.

Luckily, this is a simple repair on most vehicle models. You can replace a bad CTS in your car following a few simple guidelines and precautions. After confirming that your coolant temperature sensor has failed, follow the steps in this guide to restore engine performance and save in car repair costs.

OK. So now the question is, Can you replace the CTS yourself without much experience in car repair?

Well, that will depend on your particular vehicle model. Replacing the sensor itself is easy, getting to the sensor is another matter. The good news is that, on most cars, the sensor attaches to the cylinder head or block where you can have easy access to it. However, on some models you may need to remove large components like the intake manifold to reach it. This usually happens with V engine models. Even so, you may still be able to replace it at home. So keep on reading.

Index
Potential Symptoms of a Failed Coolant Temperature Sensor
Coolant Temperature Sensor Replacement
Two Important Facts About Coolant Temperature Sensor Replacement
A bad CTS may cause your engine to overheat even with enough coolant in the system.
A bad CTS may cause your engine to overheat even with enough coolant in the system. | Source

Potential Symptoms of a Failed Coolant Temperature Sensor

Although the next indicators may point to a bad ECT sensor, problems in a different system may also show the same symptoms. That's why it's important to troubleshoot your coolant temperature sensor before installing a new replacement.

  • Engine hard to start
  • Driveability problems
  • Diagnostic trouble codes: P0117, P0118, P0128. They'll show up on some models.
  • Poor fuel economy
  • Cooling fan fails to run (on some models)

A failed CTS can increase fuel consumption.
A failed CTS can increase fuel consumption. | Source

Coolant Temperature Sensor Replacement

OK. So now you're ready to replace the ECT sensor.

1. Park your car in a safe place where you can work comfortably and let the engine cool.

2. Place a clean drain pan under the radiator, open the radiator valve and drain about two to three quarts of coolant (or just enough to drop the level below the sensor). Then close the drain valve. This will minimize coolant waste when you remove the CT sensor.

3. Locate the coolant temperature sensor.

  • On most inline engine models (four or six cylinders), look for the sensor around the upper section of the engine block or around the cylinder head.
  • On most V8 (and some V6) engines, you may find it also around the upper part of the engine or under the intake manifold.
  • Look for a one inch diameter (approximately) nut with a two-wire electrical connector on top.


NOTE: A couple of suggestions here. If you can't locate the sensor, consult the vehicle repair manual for your particular car make and model. Also, even if your manual says that you have to remove a large component to access the sensor (such as the intake manifold) look for other, potential components you may remove instead to reach the sensor. You may find an alternative way to reach the sensor, if you have the correct tools. Your repair manual will have instructions on how to remove whatever part you need to remove.

4. Once you've reached the sensor, unplug the sensor electrical connector. Be careful when disconnecting the sensor. You may need to press a tab or pry loose a retainer wire before you can unplug the connector. Some sensors use a mounting clip you can pry off using a thin screwdriver or scratch awl.

5. Use a six point wrench, deep socket or line wrench for a firm grip.

6. Compare the new coolant temperature sensor to the old one; both should have the same configuration.

7. Depending on your particular application, install a new sealing washer, or apply a light coat of an approved sealer, or wrap Teflon tape around the threads of the new sensor (give it a couple of turns). This will keep coolant from leaking. Consult your car repair manual, if necessary.

8. Hand start and finger tight the sensor in the engine. Then tighten the sensor with a six point wrench, deep socket or line wrench. Torque the sensor to the specification listed in your repair or service manual. Apply the correct torque: Overtightening the new unit may ruin the threads or bottom out the sensor against the engine and break it.

9. Plug in the coolant sensor electrical connector.

10. Reinstall any components you may've had to remove to access the CT sensor.

11. Replace the coolant you previously drained, or refill the radiator with fresh coolant.

12. Start the engine and let it idle. Wait for the engine to reach operating temperature.

13. Check for coolant leaks around the sensor threads.

The following video will give a visual idea on replacing the coolant temperature sensor.

Two Important Facts About Coolant Temperature Sensor Replacement

  • Keep in mind that not all coolant temperature sensors are made equal. ECT sensors differ somehow in operation and rating. Buy the correct sensor for your particular vehicle make and model. Otherwise, your car computer will work with incorrect data for your engine and driveability problems will persist.
  • When replacing the sensor, closely check the weather seal at the sensor electrical connector. This weather seal is easy to misalign when you plug back in the connector, which will cause the new sensor connector to rust and fail sooner than expected.

On some models, the cooling fan will stop working with a failed CTS.
On some models, the cooling fan will stop working with a failed CTS. | Source

If you have decided to replace the coolant temperature sensor, you might want to replace the coolant in the system as well, if its service schedule is coming up, since you have to remove some of the coolant. Also, for a more complete repair job project, you may want to replace the thermostat as well. If you haven't changed it in the last four or five years. A thermostat will eventually fail and you'll find yourself removing the coolant again soon. Check the vehicle repair manual for your particular vehicle make and model. It'll have the correct coolant to use for your vehicle, identify the correct components and location and offer you the steps to follow for the maintenance job.

Replacing the CTS yourself can save you about $150 in repairs or more, depending on your particular vehicle model. And the best part is that, for most models, the sensor is readily accessible, so the averaged car owner can perform this repair at home using common tools. All you need is one or two hours of work in your garage in a Saturday morning. And if you want to keep your cooling system—and engine—working at its best, don't forget to check the system periodically, and service it at your manufacturer recommended intervals.

Questions & Answers

  • I have Nissan Rogue. I just replace the thermostat and coolant sensor, but every time I drove 20 minutes with ac on and about 70 mph the coolant sensor warning always goes on saying the car is overheating, but the engine coolant gauge is normal. What could be the problem?

    There could be a problem with the AC system, possibly a bad switch.

  • My 1998 Buick Century was running, but then a light comes on the dash that says "Hot Check All." It says it's heat sensor but the car will not restart. What should I do?

    On some models, the computer will prevent the engine from starting when coolant issues are present. Test the coolant sensor and replace it, if necessary. This post might help:

    https://hubpages.com/auto-repair/Coolant-Temperatu...

Comments

    0 of 8192 characters used
    Post Comment

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      6 months ago

      Hi Michael,

      Scan the computer for codes again and see if there're any pointing again to the TPS or something else.

      Other possible issues that can lead to a high idle speed:

      * Bad idle air control (IAC) valve/solenoid or buildup preventing the valve from proper operation - this valve is accesible and easy to test. You can even remove it for inspection. If you have the repair manual for your vehicle model (or check it at the local library) you may be able to do it yourself.

      * Take a look at the throttle body, manually work the throttle valve and look for buildup around the bore and underneath the valve - if there's buildup, clean it with carburator cleaner. Buildup can prevent the valve from operating propoerly and cause high idle as well.

      * Check that the PCV valve is not clogged or one of the connections or hoses are loose or damaged. The valve connects to the valve cover and is accessible as well.

      * Make sure the air intake ductwork is properly sealed - this containes the air filter - if there is something loose or note seal it can cause unmetered air to enter and upset engine idle.

      * Check for vacuum leaks - inspect evey vacuum hose for damage or loose connections.

      * A bad mass air flow sensor (MAF) would triger the check engine light - it there's a trouble code for it, clean the MAF sensor first, this is a common issue with this sensor, or it could be bad. The sensor is located near the air cleaner assembly and is accessible as well.

      These are the most common issues the may cause the engine to idle high.

      Good luck

    • profile image

      Michael Moore 

      6 months ago

      I took my 03 Malibu had them pit the computer on it and only thing that came up was bad tps sensor had a new one put on and it stopped idling high for little while then started doing same thing guy said only other thing it could be is throttle body really can't afford 400 bucks for it tho so don't know what I'm going to do

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      9 months ago

      Hi Jim

      There could be many reasons for an engine surging,

      the most common ones being a vacuum leak, a faulty IAC solenoid (idle air control), a bad TPS (throttle position sensor).

      Scan for possible pending trouble codes, if you haven't done so.

      Good luck

    • profile image

      Jim 

      9 months ago

      hey dan i have a 89 ranger with 2. 9. The problem is it idles at 12 to 15 00 rpms. When driving down road at f55 to 70 the rpms goes well over 3000 to 3500 rpm and then drops and then back up and keeps fluctuating. Idles real high even after warmed up. Any ideas.

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, axleaddict.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://axleaddict.com/privacy-policy#gdpr

    Show Details
    Necessary
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Marketing
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Statistics
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)