Typically, you should not use thread locker on valve cover bolts unless the factory service manual or OEM specifies it. The valve cover gasket and proper torque are usually sufficient to seal and keep the bolts secure.
Engine vibration and heat can affect valve cover hardware over time, and some engines may have specific requirements for thread locking. Because thread locker can complicate future removal and potentially contaminate the gasket seating, always start with the manufacturer’s guidance and then apply general best practices if a lock compound is advised.
When manufacturers require thread locker
Many engines rely on a gasket and torque to seal the valve cover. Some manufacturers explicitly forbid thread locker on these bolts, while others may specify a small amount or use bolts that are pre-coated. If the service manual instructs thread locker, follow the exact product and torque procedures provided.
- Follow OEM instructions: If the manual requires thread locker on valve cover bolts, use the recommended product and torque values exactly as directed.
- Choose the right product: Use blue/medium-strength thread locker (e.g., Loctite 243/242) for bolts into metal. Avoid red/high-strength Locktite on aluminum heads or where disassembly is anticipated.
- Prepare threads: Clean all bolt and threaded hole surfaces so they are dry and free of oil, old sealant, or residue before applying thread locker.
- Apply sparingly: Use only a small amount on the bolt threads; avoid coating the portion that sits in the head and any area that contacts the gasket seal.
- Sealant vs. thread locker: Do not apply thread locker to gasket mating surfaces; only apply to the threads if the manual specifies it. If a gasket sealant is required, use it as directed by the manual, not in place of thread locker unless explicitly instructed.
- Torque as specified: After applying thread locker, torque to the engine’s recommended specification. Some manuals call for re-torquing after a heat cycle or initial run, so follow those instructions precisely.
Before applying a list, note the following common practices observed in the field.
In practice, if the manual calls for thread locker on valve cover bolts, treat it as a precise instruction and follow it to the letter. If not called for, rely on a clean gasket surface and correct torque to ensure a proper seal.
When not to use thread locker
For most modern engines, valve cover bolts do not require thread locker. Using it without explicit instruction can hinder future maintenance, contaminate sealing surfaces, and complicate gasket replacement. Always defer to the service manual for your specific engine.
- Do not use thread locker on valve cover bolts unless the OEM specifies it.
- If the manual specifies sealant for the gasket, apply only to the gasket surfaces as instructed and avoid the threads that contact the gasket.
- Use new bolts and gaskets if the original hardware was locked with thread locker, as residue can affect seal and torque readings.
- Follow the prescribed torque sequence and final torque values; some engines require a retorque after a heat cycle or break-in period.
Before applying a list, consider these general cautions.
Bottom line: Unless your OEM guide says otherwise, avoid thread locker on valve cover bolts. Proper gasket condition, correct bolt torque, and appropriate sealant (if specified) are the practical keys to a lasting seal.
Summary
Thread locker on valve cover bolts is not routinely necessary and can complicate service. Use it only if the manufacturer explicitly prescribes it, and then choose a blue/medium-strength product, apply a small amount to clean threads, and torque to the specification. In most cases, rely on a fresh gasket and proper torque without thread locker, and always defer to your vehicle’s service manual for the final guidance.
How long does it take for loctite to set up on a bolt?
Cure in place
Most LOCTITE threadlockers take 24 hours to fully cure, undergoing an anaerobic chemical reaction from liquid to solid polymer. Allowing complete curing is essential for optimal performance, as premature use can hinder the adhesive from reaching its full mechanical and physical properties.
Do valve cover bolts need anti-seize?
You shouldn't need to, but they need to be replaced (they're aluminum) and torqued to 9nm on the N52K.
Should I use loctite on valve cover studs?
Loctite blue for valve cover studs works great.
Should I put anti-seize on engine mount bolts?
In general, apply an anti-seize compound to threads of bolts that need periodic removing, particularly in the case of steel bolts threaded into an aluminum casting, and bolts that experience extreme temperature fluctuations such as engine side covers and exhaust mounts.