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Engine Block Sealer And Engine Block Coating

Engine Block Sealer

Engine Block Sealer And Engine Block Coating

RustSeal and KBS Tank Sealer are excellent engine block sealer options for coating and sealing the inside of an engine block.

Why should the inside of an engine block need to be sealed?

Typically, “sealing an engine” is thought of as using gaskets to seal the surfaces of adjoining fluid filled engine components to prevent leakage. For example, a valve cover gasket, an oil pan gasket, or a main seal. However, we are referring to sealing the inside surfaces of the engine block.

Sealing the inside of an engine block, often referred to as "block sealing" or "block coating," can provide performance, durability, and maintenance benefits and solve or avoid a number of problems.

  • Porosity – Some engine blocks can be porous, meaning they have tiny holes in the casting through which oil and antifreeze can seep. This is also known as “sweating”. The holes can be caused by gases and contaminants trapped in the metal during the casting process. Sealing a porous engine block can stop seepage.
  • Corrosion - Sealing the inside of the engine block helps prevent corrosion by creating a protective barrier between the metal surfaces and the moisture and acids present in engine fluids.
  • Lubrication - By sealing and smoothing the inside surfaces of an engine block, oil shedding can be improved and prevent the accumulation of oil in certain areas. As well, it can smooth oil flow through passages. Sealing the inside surfaces of an engine block promotes more effective lubrication, increases heat dissipation, and reduces the risk of oil-related problems. Sealing the inside of an engine block addresses issues related to porosity, corrosion, and lubrication, and can contribute to the overall longevity and reliability of the engine by allowing the fastest oil return to the sump.

What surfaces are typically sealed with engine block sealant?

  • Crankcase
  • Lifter valleys
  • Other oil return passages

What are important traits of engine block sealer?

Engine block sealer needs to be able to perform in extreme environments without failing, and meeting the following criteria is highly important:

  • Adhesion - Engine block sealer must be able to strongly bond to metal to create a reliable and long-lasting seal. As well, engine block sealer must remain adhered, so it does not peel off and create problems with plugging oil filters, oil pump screens, or oil passages.
  • Flexibility - Engine block sealer must be flexible to handle engine vibrations, thermal expansion, and contraction without cracking or losing its seal.
  • Chemical Resistance - Engine block sealer should be resistant to a wide range of fluids, including engine oil and coolant.
  • Temperature Resistance - The sealant must be able to withstand high temperatures generated by the engine as well as low temperatures without breaking down or losing its sealing properties.
  • Compatibility - Engine block sealant must be compatible various metals such as aluminum, cast iron, and other alloys.
  • Durability - Engine block sealer needs to provide a durable and long-lasting seal.

Sealing engine blocks with RustSeal or KBS Gold Standard Tank Sealer

RustSeal and KBS Tank Sealer use single component moisture curing polymeric isocyanate formulations engineered to strongly bond to and seal metal creating a smooth, tough, hard yet flexible coated surface making RustSeal and KBS Tank Sealer perfect for use as an engine block sealer.

  • Incredible adhesion to prepared ferrous and non-ferrous metals to seal.
  • Excellent coating flow out for a smooth finish that improves oil shedding and oil passage flow.
  • Thorough sealing of porous engine blocks
  • Corrosion prevention
  • Flexible to allow engine block expansion and contraction with heat.
  • Impervious to fuels, oils, and chemicals.
  • Withstand temperatures up to 600F which is more than enough for oil cooled engines.
  • Incredibly durable and long lasting

Using RustSeal or KBS Tank Sealer as an engine block sealer comes down to personal preference. KBS Tank Sealer is silver-gray in color and the formulation is slightly more viscous than RustSeal for increased spreadability. RustSeal is available in a wide variety of colors.

Another consideration is the sheen of the finish, which is important for oil shedding and flow. Glossy finishes work the best. KBS Tank Sealer is glossy RustSeal comes in a variety of glossy colors.

What is the best engine block sealing procedure?

The interior surfaces of the block that will be coated must be properly prepared with KBS Klean and RustBlast to ensure strong coating adhesion.

Before beginning the preparation and coating procedure, block off/plug areas not to be coated or prepped.

KBS Klean

Before applying engine block sealer, the surfaces to be coated must be impeccably clean. Any oil, grease, grunge must be thoroughly cleaned away. KBS Klean is a concentrated cleaner that is mixed with warm or hot water and is used to scrub the inside of the block. Cleaner residue on the surface of metal can interfere with coating adhesion. When rinsed, KBS Klean leaves no residue.

Instructions for use of KBS Klean can be found HERE.


RustBlast is a powerful acid etch, rust remover and zinc phosphate pre-primer. RustBlast effectively dissolves rust, corrosion, metal oxides, and tarnish from most metal surfaces and etches the surface for best adhesion of RustSeal and KBS Tank Sealer. Surfaces to be coated are scrubbed with RustBlast and a Scotch Brite pad.

Instructions for use of RustBlast can be found HERE.

Applying RustSeal or KBS Tank Sealer to the inside of an engine block

Both RustSeal and KBS Tank Sealer can be applied with a brush, or with spray equipment.

Solvents in the coatings need to evaporate properly for the best adhesion. Light coats work better than thick coats.

Instructions for use of RustSeal can be found HERE. This same application procedure followed for RustSeal is followed for KBS Tank Sealer in this circumstance because you are brushing or spraying the KBS Tank Sealer.

Want to know more?

Have questions about how to seal and coat the inside of your engine with paint? Please reach out HERE!