Blue Threadlocker Basics

    February 20, 2014

Have you ever questioned which Loctite® Medium Strength Blue Threadlocker to use? Did you even know there are multiple kinds?

Of all our thread treatment applications, the Medium Strength Blue Threadlockers are the most commonly used. They are removable with standard hand tools on ¼ ” to ¾ ” fasteners, have fast fixture times, and are available in liquid, stick, paste, gel and tape form. The only question is which blue threadlocker is right for your particular use?

The four types that I will be discussing are:

  • Loctite® Threadlocker 242™

  • Loctite® Threadlocker 243™

  • Loctite® QuickTape® 249™ Blue Threadlocker Tape

  • Loctite® Blue Stick Threadlocker

Note: Although all Loctite threadlocker BOTTLES are red, the LIQUID in all four of the below products are blue. The red bottle is what distinguishes Loctite® threadlockers from other brands. Learn about the difference between Red, Blue, Green and Purple Threadlockers

Loctite® Threadlocker 242™ 

The typical repairs that utilize this type of medium strength threadlocker range from valve cover bolts to carburetor studs. This is known as our all-purpose threadlocker, and is also known as the “original threadlocker.” It eliminates the need for expensive lock nuts and lock washers, seals even when it vibrates, and protects threads from corrosion. 

Loctite® Threadlocker 243™   

Loctite 243 threadlocker is an upgraded version of Loctite 242, and is more of a general-purpose member of our “blue crew.” It is designed to have improved oil tolerance with surface-insensitive properties (plated fasteners no longer require primer), combined with the same overall benefits of the original Blue Threadlocker 242. Projects that would need this type of application include rocker studs, oil pans, disc brake calipers, pulley assemblies and many more.

Loctite 242 and 243 liquid blue threadlockers were so successful that we created two alternative physical forms of the product, for easier use on a wide variety of applications, described below: 

Loctite® Stick Threadlocker

Loctite Sticks are created in a semi-solid form, for easy over head applications. They are small enough to be “pocket friendly,” and will not leak, drip, or spill. They are also available for primerless and oil tolerant applications. 

Loctite® QuickTape 249 Threadlocker 

Loctite QuickTape is suppilied in a low tack film to provide a convenient and easy to use package, especially where a liquid product may be too fluid to stay on a part or may be difficult to apply. This product can be used for immediate assembly or days later, and provides consistent strength on a variety of metal substrates.

WATCH how to apply below. For more Loctite how-to, check out our YouTube Channel.

Both the stick and tape threadlocker products are used for difficult repairs and overhead applications, and both can be used for cleaner application purposes. They are most commonly used on applications that involve valve cover bolts, rocker arm adjustment nuts, carburetor studs, etc.  

Note: The threadlockers linked above are Automotive Aftermarket products. For Industrial Assembly & Maintentance threadlockers, click here.

Now that you know the basics and the differences among our “blue crew” of threadlockers, it’s easy to see the benefits that each one can bring to help you complete every project with precision and quality.

You might also be interested in: When and Why to Use Purple Threadlocker

About the Author, Andy Scott

Andy Scott has been with Henkel for 7 years and is currently an application engineer. He started with Henkel in 2007 as an intern while attending school. He earned a Bachelors Degree in Mechanical Engineering from Central Connecticut State University. Andy has been interested in how anything and everything mechanical works from the time he could walk. From his personal and professional projects, Andy has brought his expertise in fabricating and building cars, trucks and ATVs.

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23 responses to “Blue Threadlocker Basics”

  1. Kyle says:

    Hi Andy,

    Great post!

    Do you know if Loctite still manufactures the 249 Threadlocker Tape?

    I’ve had difficulties locating a retailer to supply it.

  2. Andy Scott Andy Scott says:

    Hi Kyle, glad you enjoyed it. Sorry for the delay in response. Yes, we still make the 249 Threadlocker Tape. You should be able to find it at your local NAPA Auto Parts or online at You can also search for other local distributors using our distributor locator here: – Andy

  3. William Baker says:


    I have removed some small machine screws that have 243 on them. What solvent and method should I use to clean them prior to reinstalling?

    • Brandon Gearing says:

      Hi William,

      You can use a wire brush to clean the threads and use the most aggressive organic solvent you have handy. These can include: methylene chloride, acetone, MEK, brake cleaner, etc.

  4. Sylvain says:


    Can we use loctite 242-243 on parts that are at minus 15 celsius or we have to heat them before applying thread locker?

    • Brandon Gearing says:

      Hi Sylvain, thanks for your question. We do not recommend any use of our products below 10C/50F as they won’t cure in the cold. You would need to set up a booth and heat up the parts and air for 24 hours. Thanks, Brandon

  5. Dave Gooch says:

    Your products have a best before date on them. What happens when they are older than that? Is it a gradual decrease in effectiveness? Realistically, how long can I keep using the product after that date?


    Dave G

    • Daniel Wergeles says:

      We do not advise the use of expired products. However if you do decide to use it, compare the expired product to a current product. Use the color and the viscosity of the products as a bench mark. If they are not too different then you maybe ok. It’s hard to say how long one can still use a product after the expiration date because it is all depending on how the product was stored.

  6. Bill Swift says:

    Hi Andy,
    I run compression ignition model airplane engines in the range of 14,000 rpm. They are small, .15 cu. in., and have adjustable compression via an M6x.75 screw. This screw spontaneously loosens at certain frequencies. I have Loctite 242 but wonder if it is appropriate in an application where the compression screw needs to be adjustable, but remain set at optimum rpm. Thanks, Bill

  7. RANDALL MOOR says:

    Will these products work in a pool filter – are they waterproof?

    • Sara Lopes says:

      Hi Randall, thank you for your question. Yes, when the product is fully cured. These products are for metal to metal applications only, so we advise to not get them on plastic pool parts as it can cause stress cracks. Stainless and aluminum metals will need primer 7649. If you have any additional questions, please call our tech support line at 800-562-8483. Thank you!

  8. Ken Kalbfell says:

    Hardware (10-32) had 242 on some time ago. For a repair, the screws were removed. We will use new screws but it is difficult to remove all the 242 from the internal threads. Will a re-application of 242 or 248 on the screw threads work at all?

    • Sara Lopes says:

      Hi Ken, thank you for your question. If you can’t remove all of the old residues, new 242 will still cure and lock this. You might see a slight variation in strength, but probably not a big difference. The liquid 242 would probably work better than the stick 248 under these conditions. Of course, all of our standard testing is done on dry, clean threads and not threads with residue of old, previously used product on there. Please test under your own actual conditions.

  9. Gary S says:

    I had a pivot pin on one of my boxlock shotguns slide out enough that one of the triggers came loose. I was thinking about putting some Blue Loctite on each end of the pin thinking this would prevent it from slipping in the future. However, I want to be able to remove the pin if necessary later. Is this an appropriate application? I was thinking the 243 would be best because of the oil used when the gun is cleaned. Your thoughts please. Thanks in advance for your reply.

    • Sara Lopes says:

      Hi Gary, the 243 sounds appropriate for your project. If you want to discuss your situation further, please call our tech line at 800-562-8483.

  10. ger bos says:

    For the securing of bolts in a malmedy toothed coupling the use of loctite 2400 is recommended.
    what is the difference between loctite243 and loctite2400

    • Sara Lopes says:

      Hi Ger Bos, thank you for your question! Both products are medium strength threadlockers. Loctite 2400 is a European product that is a non-skin irritant, unlike most anaerobics. The US version is Loctite 2400NA. If you’d like to discuss your these two products in greater detail, please call our tech line at (800) 562-8483. Thank you!

  11. RANDY MATTHEWS says:

    loctite 248 37087
    stick type …why does it seem to make a hard crust on the top of it ? … seems like i am waisting 2 mm of product , if i dont use it everyday …

    • Sara Lopes says:

      Hi Randy, we’re sorry to hear that you’re experiencing issues with our product. If you can please call 1-800-LOCTITE or email, one of our tech representatives would be more than happy to help solve your problem. Thank you!

  12. JOHN T BELKNAP says:

    Can I pre-apply blue loctite with the solid stick for my customers to assemble at a later date, and if so how long can they wait to activate it by attaching the other metal? I am bonding aluminum to SS316 and SS316 to brass. Thanks!

    • Sara Lopes says:

      Hi John, in order to give you our best recommendation, please contact us at (800) 562-8483 and select option #1, where we’ll be more than happy to further assist you with your question. Thank you!

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