Does A Thermostat Gasket Need Sealant? (Know It Now!)

does a thermostat gasket need sealant

Thermostat gaskets are small pieces of metal ideally designed to provide a seal between your vehicle’s engine and the thermostat housing. Even though thermostat gaskets are small, they are an essential component of your vehicle’s cooling system, and they can easily cause extensive damage if something is wrong with them. If a thermostat gasket fails, your vehicle’s engine will overheat and eventually blow the head gasket. Your vehicle’s engine and other essential components will suffer extensive damage when this happens.

Does a Thermostat Gasket Need Sealant?

Sealant is not always necessary because most thermostat gaskets have a practical design that makes them leakproof. Sometimes you may jam the thermostat gasket by simply applying too much sealant. However, if your vehicle has an old thermostat gasket or you have dealt with leaking problems in the past, applying a thin layer of sealant will not cause any harm.

In fact, this will help you make the thermostat gasket leakproof. But, you need to be mindful not to apply too much sealant.

It is also worth noting that some thermostat gaskets come with adhesive backing, which is enough to keep it in place. The adhesive backing also prevents leakages while making it easy to open the thermostat gasket when needed.

What Kind of Sealant for the Thermostat Gasket?

The sealant that secures your thermostat gasket in place without affecting its functionality and lifespan is the best sealant. Such a sealant protects the thermostat gasket from excess engine heat and corrosive compounds found in fuel and oils that can easily damage the gasket over time.

The following are the different types of sealants that may work well with a thermostat gasket:

RTV (Room Temperature Vulcanizing) silicone sealers

These sealants are available in many colors, and they come in different depending modes, including tubes, caulk-gun style cartridges, and aerosol cans. The different colors indicate the heat tolerance of a particular sealant.

Copper is mainly used for situations of up to 750 degrees. Orange and red are for situations of up to 650 degrees. On the other hand, blue, gray, and black are best suited for up to 500 degrees.

Car and truck manufacturers recommend car owners use the ultra version of the RTV silicone sealers for modern electronically-controlled vehicles.

Copper sealants

These sealants are available in aerosol and brushable forms, and professional mechanics mostly use them for exhaust manifold and head gaskets.

Copper sealants are fast-drying, and they easily cover the smallest imperfections in the metal. As a result, copper sealants create a strong seal that dissolves heat.

These sealants also perform well in distributing heat uniformly among mating surfaces. Additionally, these sealants can withstand up to 500 degrees and are easy to remove even months after installation.

High tack

These sealants are available in tubes and brush-top bottles, and they can handle up to 500 degrees. One of the best things about high tack sealants is that they are resistant to propane, kerosene, and diesel fuel. They remain intact long after installation.

Anaerobic sealants

Anaerobic sealants come in a tube, and they are red in color. These sealants are mainly used by technicians in situations where there is insufficient air to aid the drying process.

Anaerobic sealants were developed to meet OEM’s specifications for non-corrosive gasket makers in metal-to-metal situations.

These sealants are suitable in situations where a replacement is not readily available or where there was never a gasket in the first place.


Also known as Indian Head, shellac sealants are best-suited for cardboard and thin paper gaskets installed in low-temperature (between 300 and 350 degrees) and low-pressure environments.

These sealants are resistant to motor fluids, and many technicians use them to mount differential cover gaskets, timing covers, and thermostats. Shellac sealants are easy to remove even long after installation.

Gasket makers

These sealants come in three different kinds: non-hardening, fast-drying/fast-hardening, and slow-drying/brushable. All three versions form gaskets that can handle up to 400 degrees.

However, the three versions have different purposes. Technicians use fast-hardening/fast-drying gasket makers to block expansion plugs, create threaded connections and create definite seals between metal-to-metal surfaces.

Slow-drying and brushable sealants are used on neoprene transmission pan gaskets and coil oil pan gaskets. This is mainly because they are easy to clean compared to the other versions. On the other hand, non-hardening gasket sealants are mainly used for hose connection seals.

How to Put Sealant on the Thermostat Gasket?

The following are the steps you need to follow when putting on sealant on a thermostat gasket:

  • Ensure that the engine is adequately cool. Installing sealant with an overheated engine can shorten its lifespan. Plus, you risk burns. It is safer to apply sealant when the engine is completely cool.
  • Drain the engine of any remains. If you do not do this, it will decrease the engine’s ability to lubricate.
  • Remove the thermostat before you proceed.
  • Remove the radiator cap after the engine completely cools down. If the engine is still hot, you cannot remove the radiator cap safely.
  • Shake the head gasket sealant container well.
  • Apply the sealant properly and top off the radiator with the coolant.
  • Replace the radiator cap carefully.
  • Start the engine.
  • Use the climate control button or key to set the maximum heat.
  • Keep the engine’s RPM at 1000 rotations for at least 15 minutes.
  • Turn off the engine, then allow it to cool for at least an hour.

How Long Should I Wait After Applying Thermostat Gasket Sealant?

RTV sealants usually take two hours to set up and approximately 24 hours to cure. On the other hand, anaerobic sealants and gasket makers take an hour to cure.

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