Every engine builder has its own preferences regarding gaskets. Some swear by them, while others swear at them. Some never use them, while others can’t do without them.
The truth is that gaskets are usually not necessary, but they can be helpful in certain situations. Valve cover gaskets are designed to seal the engine against leaks.
If they were not coated with a material that resists combustion gases, they would quickly deteriorate and fail. It is said that if silicone seals were placed on engine blocks, the blocks would inevitably leak oil due to the acidic nature of the silicone.
Best sealant for valve cover gaskets-Permatex High Tack Gasket Sealant
Permatex Gasket Sealant is an all-purpose sealant that can be used to hold gaskets in place during assembly as well as sealing cut gaskets.
It is sensor-safe and provides excellent adhesion to a wide variety of surfaces.
Permatex Gasket Sealant is formulated with a tackifier resin that helps the sealant remain tacky indefinitely. Because the sealant remains tacky even after it has dried, it continues to resist leakage until mechanical fasteners have been applied.
Permatex Sealant can be used on rubber, cork or paper gaskets where sealants are prone to creep or where multiple disassembly/reassembly operations may occur.
Warnings: Flammable. Keep away from open flame or ignition source. Vapors will accumulate readily and may ignite explosively.
Should you use sealant on gaskets? Here’s why:
Gasket sealants are designed to be flexible in order to conform to the surface they’re sealing. The parts they touch will constantly expand and contract with temperature changes, so if you use something like silicone as a sealant, it will expand and contract at the same rate as the rest of the engine parts and won’t last long before becoming brittle and breaking down.
Rubber valve cover gaskets are designed to seal against the valve covers and thus need silicone to make a good seal. This prevents combustion gases from leaking past the valve cover and contaminating the engine’s lubricating oil, which could cause damage to other components.
First of all, keep in mind that the silicone or sealant is there to prevent oil from leaking out of the engine. It will not stop water from getting into the engine.
The oil that leaks out is usually burning oil being pushed out by the piston rings as they go around and compress the oil against the cylinder wall.
The compression lifts some of the oil off of the cylinder wall, but most remains on it until it is pushed out by the next ring going around. If you are getting water into your spark plug holes, then you may have a bad head gasket or loose valve cover gaskets.
Rubber valve cover gaskets will leak if they get brittle and break down. If they stay soft, then silicone or sealant should not be necessary. One way to prevent this is to use high-quality silicone or sealant when you first install a new set of valve covers.
Should I use silicone on valve cover gaskets?
Can you use silicone on rubber gaskets? The short answer to your question is: No, you should not use silicone on rubber gaskets. Silicone is a lubricant and sealant that works great with metal. It doesn’t work well with rubber, however.
Silicone vs rubber valve cover gasket
Rubber is porous and will absorb silicone. When the silicone-saturated rubber encounters a hot engine, it will soften excessively and allow air to pass through the seal.
You might also find that the silicone will turn into a sticky goo when it gets hot, which makes it even worse for sealing.
Silicone sealant also acts as a lubricant when tightening down the valve cover to prevent it from stripping out threads on the engine block or breaking studs.
Adding silicone sealant directly to a rubber gasket can help it make a tighter seal between two metal parts (the engine block and valve cover, for example).
The manufacturer of most rubber gaskets recommends using sealant when installing new gaskets or in situations where there is excessive leakage from old gaskets.
Many people believe that silicone needs to be used with all rubber parts because it is made from silicon and will eventually deteriorate without it.
A few words of caution before I get into the details:
Silicone can be a messy material to work with; it’s best to avoid getting it on your hands or on anything that isn’t silicone-safe.
It also doesn’t hold up well under heat, so it should only be used on the outside of the gasket cover and nowhere else (such as on the bottom-end). It can also stain your engine blue when it’s cold.
If you’re working with an aluminum cylinder head and an aluminum gasket cover, you don’t need to apply any sealant to either surface — both are already equipped with excellent natural seals.
However, if you’re using a steel valve cover on an aluminum head (or vice versa), apply silicone to both surfaces before assembly.
If you’re not sure whether you should use silicone or not, err on the side of caution and don’t use any sealant at all.
How to install rubber valve cover gaskets?
Frequently Asked Questions
1. How Do I Seal My Gaskets?
Silicone sealant goes between the rubber gasket and the surface it’s sealing against. It’s important that you apply a thin layer (around 1/8 inch) of silicone over the entire surface of the gasket. Don’t worry if some seeps through onto other surfaces because it won’t cause any problems there.
2. How Long Does Sealant Last?
A thin layer of sealant will last for years and years without drying out or breaking down, but you’ll need to reapply it if you take off your cylinder head at any point as this will remove small amounts of silicone.
3. Do cork valve cover gaskets need sealant?
You can glue the gasket to the cork valve cover.
Gasket adhesive helps hold cut gaskets in place during assembly and seals cut gaskets. You can use Permatex High-Tack Gasket Sealant will adhere permanently to rubber gaskets and the surface that you apply.