Loctite 243 Medium-Strength Threadlocker (Oil-Tolerant) — Removable, Sets in 10 min

Loctite 243 is a medium-strength, oil-tolerant anaerobic threadlocker that secures metal fasteners against vibration while still allowing disassembly with hand tools.

Designed for automotive and general-purpose metal assemblies, Loctite 243 (formerly "Blue") bonds to stainless steel, aluminum, and plated surfaces even when light oil contamination is present. It cures anaerobically between metal parts, sets in about 10 minutes, and reaches full strength in 24 hours. Rated for fasteners from 6 mm to 20 mm (1/4"–3/4"), this threadlocker resists shock and chemical exposure while providing a stable joint up to roughly 140°F (60°C).

How quickly does Loctite 243 set and reach full strength?

Loctite 243 begins to set within approximately 10 minutes after application, allowing you to handle assemblies sooner. Full cure and maximum strength typically develop within 24 hours under normal conditions.

• Initial handling time: ~10 minutes
• Full cure: ~24 hours
• Cure depends on metal contact and absence of oxygen in the bond gap
• Ambient temperature influences cure speed

Which fasteners and environments is this threadlocker suitable for?

Loctite 243 is formulated for general automotive and industrial fasteners from 1/4" to 3/4" (6–20 mm). It performs well in assemblies exposed to vibration, thermal cycling, and common automotive fluids.

• Recommended bolt range: 6 mm–20 mm (1/4"–3/4")
• Uses: rocker studs, oil pans, alternators, calipers, pulleys
• Resistant to light oils and common automotive chemicals
• Removable with standard hand tools when needed

What metals and surface conditions will it bond to effectively?

This anaerobic formula bonds reliably to a wide variety of metals, including stainless steel, aluminum and plated surfaces. Its improved oil tolerance lets it cure where traces of oil remain, though clean, degreased surfaces provide the best long-term performance.

• Compatible with stainless steel, steel, aluminum, and plated parts
• Designed for somewhat oily surfaces but better on cleaned parts
• Forms a strong bond in the absence of air between mating metal surfaces
• Ideal for assemblies subject to vibration and shock

How is Loctite 243 removed or serviced if disassembly is required?

Loctite 243 is a medium-strength threadlocker intended to prevent loosening while allowing disassembly with common hand tools. For stubborn joints, heat or mechanical force can assist removal, and specific Loctite removers are available for tougher applications.

• Designed to be removable with standard hand tools
• Applying controlled heat can reduce strength for disassembly
• Loctite solvent removers can aid in difficult cases
• Mechanical impact or torque may be necessary on older cures

Who is this for: Loctite 243 is aimed at automotive technicians, home mechanics, and industrial maintenance crews who need a reliable, medium-strength threadlocker that tolerates light oil contamination. It suits anyone fastening bolts and nuts in engines, drivetrains, housings, and assemblies where vibration or chemical exposure can cause loosening but future disassembly may still be required.