How to Use Liquid Glass To Seal A Blown Head Gasket

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Liquid glass -- aka "sodium silicate" -- is a fascinating substance with many uses. It's easiest to imagine sodium silicate as little spheres of silica sand formed around grains of salt. The tiny spheres rapidly soak up water, turning into a kind of gel. Once the gel is dried out and exposed to heat, it quickly forms into a very hard shard of pure glass. These shards can do a fine job of sealing blown head gaskets in some applications, but it's best to study ahead before pouring liquid glass into your cooling system and assuming the best.

Things You'll Need

  • Liquid glass sealer
  • Wheel chocks
  • Floor jack
  • Jack stands
  • Drain pan
  • New coolant
  • Screwdriver or pliers -- optional
  • Funnel
  • Determine your engine type and set your expectations. If you have an aluminum engine block or heads, consider a more specialized product -- see the "Tips" section. Liquid glass by itself is always a temporary fix, but aluminum expands much faster than iron. This will cause the sealing glass by itself to fracture and fail in a matter of months, rather than a few years as in an all-iron engine.

  • Park the vehicle on level ground and allow the engine to cool completely. Liquid glass, in itself, is compatible with all coolant types, including standard green coolants -- which already contain silicates -- and newer organic acid technology, or "OAT" coolants. Consequently, there's generally no need to drain your old coolant before pouring the sealant in.

  • Add the sealant to your radiator through the radiator cap. If your radiator doesn't have a cap, add the sealer to the radiator through the upper radiator hose. Chock the rear wheels, set your parking brake, lift the front of the vehicle with a floor jack and secure it on jack stands. Place a drain pan under the radiator, and turn the petcock drain valve on the bottom of the radiator counterclockwise. Drain about a gallon of coolant out and close the valve.

  • Remove the upper radiator hose from the radiator with a screwdriver or pliers, and insert the end of your funnel tube into the hose opening in the radiator. Pour the entire contents of the bottle into the funnel and into the radiator. You can top the radiator up with some fresh antifreeze afterward, if you like. It's important that you pour the liquid glass directly into the radiator, instead of the radiator overflow bottle, as you normally would with coolant. Reinstall the upper radiator hose.

  • Start the engine, and allow it to idle for 20 minutes. Don't rev it up to get it up to temperature faster; this will cause the water pump to force coolant through the leak in the head gasket before the metal is up to temperature, preventing the liquid glass from hardening and establishing a seal. Simply allow the engine to idle up to temperature, and keep idling until the 20 minutes has elapsed.

  • Shut the engine down and allow it to cool completely. You can repeat the idling, heating and cooling cycle a few more times if you wish. Each one will give more liquid glass another chance at sealing cracks that the last cycle might not have. When you're finished, check the engine's condition. It should be running much smoother.

  • Drain all of the coolant, and refill the engine with the coolant and mixture your manufacturer recommends. There's no point in having liquid glass floating around, chewing up your water pump and clogging your coolant passages if it's already done its job sealing the head. After refilling the system, "burp" it by adding coolant to the "HOT" fill line on your overflow bottle, bringing the engine up to temperature and allowing it to cool completely. Top up the bottle as necessary to maintain level as the engine cools. Keep repeating this cycle until the engine stops taking fluid, and the level stabilizes at the "COLD" fill line after the engine cools down.

  • Change your oil and filter. If you had a blown head gasket, there's a very good chance that your oil looks like chocolate milk -- a sign of water in the oil. That's bad enough, but now there's very likely some liquid glass in the oil, too.

Tips & Warnings

  • There's a common misconception that block sealers that utilize liquid glass can't be used on aluminum engines at all. This simply isn't true. The theory goes that because aluminum expands much more than iron, it will expand away from the brittle glass plug, and the plug will break free. But the glass seal forms when the engine is hot, when the metal's already expanded. It's when the engine shrinks back down to size again that the metal can squeeze the glass plug into fracturing and failing.
  • Sealer manufacturers are well aware of this, which is why you'll rarely find liquid glass used by itself in these applications. Most often it's mixed with copper, aluminum or other particles and fibers designed to give it some flex under expansion and compression. True, there are different, specialized formulations for iron and aluminum engines, and you should use the one designed for your application. But in these formulations, the liquid glass is essentially just a bonding agent, and the particulates suspended in it are doing most of the work.

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  • Photo Credit Nastco/iStock/Getty Images
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