Composite and silicone gaskets seal metal-to-metal surfaces in today's engines. Plenums, carburetors, head covers, valve covers, exhaust systems and oil pans all use gaskets to match surfaces perfectly, control air and fluid pressure and to prevent leaks. Composite gaskets are just that-a variety of materials (cork, paper, rubber, felt) combined together and designed for specific applications. A gasket sealant or adhesive usually aids their assembly and function. Silicone (or formed-in-place) gaskets are created from a special compound that is applied directly to the parts in question and is allowed to cure in place.
Today's engines run at high rpm and at high temperatures. They are often constructed of various alloys that expand at different temperatures and rates as heat builds. And most modern engines use computer controls that are extremely sensitive and prone to misbehavior should they sniff some unfamiliar compound in their midst. For all these reasons and more, make sure that gasket and sealant compounds are designed for your vehicle, engine and application.
Please read these guidelines through before proceeding. Vehicle and service manuals should also be at hand.
Stay Safe
Appropriate maintenance and service procedures will keep your car in the pink and you out of the emergency room. So whenever you're working on your vehicle, please do the following:
> Keep a first-aid kit nearby.
> Observe caution around sharp and hot objects. Cars have plenty of them.
> Use safety ramps under the frame or jack stands if you find you must raise your car or truck.
> When running the engine, make sure the immediate environment is well ventilated.
> If you need to ingest nicotine while working on your vehicle, don't smoke: use nicotine gum, and you won't set things (such as yourself) on fire.
Parts List
> Gasket material (composite or silicone)
> Chemical gasket remover
> Gasket scraper or putty knife
> Aerosol brake cleaner
> Straight edge
> If no lock-washers are present, thread-locking compound (medium strength)
> Torque wrench
Silicone Gasket Installation
> Make sure the engine is cool.
> Surfaces that mate must be thoroughly cleaned. Brake cleaner will remove oily residue. Rough cleaning may be done with a putty knife, but be careful not to scar light alloy surfaces. You may opt to use a chemical gasket remover instead.
> Eye surfaces for warps, creases and dents, using a straightedge, if necessary. Get new parts if needed.
> Replace worn bolts.
> Unless the gasket's enclosed instructions say otherwise, apply a 1/8-inch bead of silicone gasket material to the part at approximately a 45-degree angle, making sure the material encircles all boltholes.
> Join the parts together immediately, taking care not to squeeze out the silicone material.
> Torque parts together, wrenching bolts in the proper sequence.
> If you've used room-temperature vulcanizing silicone gasket material, you won't have to re-torque the bolts.
> Wait an hour for the silicone to vulcanize, and then re-torque the bolts.
> Start the vehicle and check for leaks.
Composite Gasket Installation
> Make sure the engine is cool.
> Surfaces that mate must be thoroughly cleaned. Brake cleaner will remove oily residue. Rough cleaning may be done with a scraper or putty knife, but be careful not to scar light alloy surfaces. You may opt to use a chemical gasket remover instead.
> Eye surfaces for warps, creases and dents, using a straightedge, if necessary. Get new parts if needed.
> Replace worn bolts.
> Apply sealant to the composite gasket and mount it to the covering part.
> Apply sealant to the second surface, applying additional layers if the part is damaged in any way.
> Apply medium-strength thread-locker to mounting bolts.
> Install the cover, torquing bolts to spec in an X-pattern to ensure a uniform seal.
> Start the vehicle and inspect the surfaces for signs of leakage.
Installation Tips
> Make sure all of your supplies and tools are close at hand before starting the job.
> Take your time.
> A repair manual specific to your vehicle may provide valuable details that this article cannot address.
> If the car hasn't cooled adequately, wait, and in the meantime, beware of hot objects.
> When choosing sealant, consider features, temperature range, pressure range and application ease.
> Do not over-torque bolts.
