Do valve cover bolts need sealant?

Generally, valve cover bolts do not require sealant; the valve cover gasket is designed to seal the joint on its own. Sealant is only appropriate when the manufacturer specifies it or when the surface is damaged or nonstandard.

The way a valve cover seals the top of an engine can vary by design and manufacturer. In most modern engines, a properly installed gasket provides the seal, and the bolts simply clamp the cover in place. However, some engines and gasket kits call for a small amount of RTV silicone or other sealant in specific locations, such as at the corners or ends of the valve cover, or when replacing a gasket that requires adhesive to hold it during installation. Using sealant against the factory instructions can lead to leaks, gasket deformation, or seepage around the bolt holes, so it’s important to follow the exact guidance for your engine.

How valve cover seals work

The valve cover sits atop the cylinder head and is sealed by a gasket that bridges the joint between cover and head. The bolts simply apply clamping force to compress the gasket evenly. An over-tightened bolt, contaminated surfaces, or a degraded gasket can cause leaks, but adding sealant to the bolt threads or under the gasket is not a universal fix and can create new problems if not recommended by the manufacturer.

Sealant guidelines

The following scenarios cover common guidance about when sealant may be involved in valve cover installations. Read them with your vehicle’s service manual for engine-specific instructions.

• When the OEM service information specifies RTV silicone sealant at certain joints or corners. Some gasket kits include instructions to apply a small bead of sealant at the ends or around spark plug wells where the gasket design leaves a gap.


• When the surfaces are damaged, warped, or corroded, and the gasket alone cannot establish a reliable seal. In such cases a technician may need to address the surface condition before re-sealing.


• When using a gasket type that requires adhesive or sealant to hold the gasket in place during installation. Some designs use a gasket that is temporarily held with sealant or adhesive in specific sections.


• On certain makes/models with known leakage areas at the valve cover ends; the manufacturer may call for a dab of sealant to mitigate persistent leaks. Always defer to the factory instructions for your engine.

Following the manufacturer’s guidance is essential. Misapplying sealant can trap oil, create uneven sealing pressure, or contaminate the gasket surface, potentially causing leaks after reassembly.

Installation best practices

The following steps help ensure a leak-free valve cover installation, whether you use sealant or not. This list assumes a standard gasket-mount setup and emphasizes general prudent practice.

• Clean both mating surfaces thoroughly to remove old gasket material, oil, and debris. A clean surface is essential for a proper seal.


• Install a new valve cover gasket that matches the engine and cover. Do not reuse a degraded gasket.


• If the service manual requires sealant, apply it only in the locations specified and use the exact type and amount recommended. Do not apply sealant to bolt threads or over the entire gasket surface unless instructed.


• Lightly oil the gasket’s mating surface if the manual permits; avoid lubricating the sealing surfaces themselves, which can affect gasket seal.


• Torque the valve cover bolts to the manufacturer’s specification in the recommended sequence (usually a crisscross pattern). Do not over-tighten, as that can crush or distort the gasket.


• After installation, run the engine and check for leaks once the oil pressure stabilizes and the gasket has seated. If a leak appears, recheck torque and, if needed, reseat the gasket per manual guidance.

Proper installation is as important as the gasket choice. Deviating from the recommended procedure can lead to leaks or gasket failure, even when the correct parts are used.

Manufacturer guidance varies

Valve cover seal practices differ by manufacturer and engine family. Some brands lean toward a no-sealant approach with a high-quality gasket, while others specify small amounts of RTV in particular spots. If you’re unsure, consult the official service manual or the gasket kit instructions for your exact engine code. When in doubt, err on the side of manufacturer guidance rather than relying on generic tips.

Summary

In most engines, valve cover bolts do not require sealant because the gasket provides the seal. Sealant is appropriate only when the factory manual for your engine specifies it, or when repairing surface damage or using a gasket that requires adhesive in certain spots. Always follow the exact instructions for your engine, ensure clean mating surfaces, and torque to the recommended specification. A careful installation coupled with the correct gasket type is the reliable path to a long-lasting seal.

Can over torquing bolts cause a gasket to leak?

Leaks and Safety Risks: Overtightening can result in the gasket being unable to maintain a proper seal, leading to fluid or gas leaks. Leaks can cause equipment damage, environmental contamination, and pose safety risks to personnel.

Do valve cover bolts need to be torqued?

Depends on the valve cover. If it's an old type pressed steel one that sits on a 1/4″ thick cork gasket then no. If it's a cast aluminium one that mates to a cast aluminium cylinder head with either a thin gasket or no gasket and just a thin smear of sealant, then yes.

What is the best sealant for valve covers?

Rtv. Permatex has always worked well for me on valve covers.

Do I need to use sealant on valve cover gasket?

Valve cover gaskets often do not require sealant, but specific areas like corners or seams where different parts meet may need a small amount of RTV silicone. Always check your vehicle's service manual to see if sealant is specified for your engine, as applying it where it's not needed can cause leaks or make future removal difficult.
 
This video demonstrates how to apply RTV sealant to specific areas of a valve cover gasket: 1mFel-Pro GasketsYouTube · Feb 4, 2021
When to use sealant

• At sharp corners or seams: Apply a small dab of RTV silicone where the valve cover gasket meets a corner, such as where the timing cover joins the cylinder head. 
• To hold the gasket: Some mechanics use a light smear of sealant to help hold the gasket in place during installation, particularly if the gasket is prone to shifting. 
• Follow the service manual: The most important rule is to follow the manufacturer's specific instructions. If the manual calls for sealant in certain spots, use it. If it doesn't, don't. 

This video shows how to apply high-tack gasket sealant to hold the gasket in place during installation: 56sDentside DepotYouTube · Mar 23, 2024
When to avoid sealant

• Do not coat the entire gasket: Applying sealant over the entire surface of the gasket is unnecessary and can cause it to squeeze out or create a leak path. 
• For modern rubber gaskets: Many modern, molded rubber gaskets are designed to seal on their own without any sealant. Using sealant can interfere with the gasket's ability to seat properly. 
• When the gasket is new: A new gasket should be able to create a proper seal. Applying sealant can sometimes hinder this, especially if the gasket is designed to compress evenly.