How To Use

Steel Seal is a simple pour-in fix for blown head gaskets. Follow our simple instructions below for 3 easy steps to a successful repair…



Head gasket failure is a symptom, not the cause of overheating. The original source of cooling system failure, if still present, must be repaired before attempting to repair your head gasket.


Steel Seal is compatible with most antifreezes, but also works in clean water. We do not recommend using Steel Seal with long life / extended antifreeze. If completing the treatment with water only, simply follow the steps above with plain water and add antifreeze afterwards for best results. Once repaired, drain Steel Seal from the cooling system and replace with your preferred antifreeze.

WATER IN OIL If water is present, you must change the oil and filter before proceeding. Change oil and leave one quart low. Add last quart after the repair is complete.

Recommended Dose

Up to 2.5 Litre engine – 1 Bottle

Up to 4.0 Litre Engine – 2 Bottles

Over 4.0 Litre Engine – 3 Bottles

Treatment Steps


Ensure engine is cold and remove the radiator cap. Pour Steel Seal directly into the radiator. Replace cap. NB: If you don’t have a radiator cap pour directly into the expansion tank.


Turn heater and fan to maximum. Start engine and run the vehicle up to temperature. Once vehicle reaches operating temperature, idle for 30 minutes. Turn off vehicle and allow to cool completely. Top up with antifreeze/water as necessary and replace radiator cap.


Leave the Steel Seal in your system and drive the vehicle as usual.

Additional Steel Seal Directions:

NB. If you are introducing Steel Seal via an expansion tank please make sure that there is sufficient room for Steel Seal to go directly into the cooling system and that it does not just sit in surge / expansion tank reservoir.

For best results:

If you have tried inferior products flush your cooling system with clean water after disconnecting bottom radiator hose. Do not use a flushing agent.

If you have flushed system reconnect bottom radiator hose.


These directions are for people that have a lot of back pressure building up in the cooling system, usually shown as bubbling in the header tank or air forcing past the coolant cap.

  • Locate the cylinder causing the bubbling in the overflow tank or backpressure. (Remove plugs one at a time till bubbling stops)
  • Before starting the engine, remove the spark plug or injector from the cylinder that was causing the bubbling in the overflow tank or back pressure. If accessible, remove injector wire from that cylinder. This will limit the amount of unburned fuel going into the combustion chamber.
  • If you cannot find the spark plug/cylinder that is causing the back pressure, run the engine with the coolant level down to the top of the radiator core and with the radiator cap off or leave the expansion cap off the expansion bottle with water only just visible.


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At Steel Seal we don’t just believe in selling chemicals or offering cheap temporary fixes, our aim is to get drivers back on the road, permanently. This is why if you have a blown head gasket and have followed the instructions above without success, we will provide a full refund under our guarantee. Or if the symptoms return after 30 days we will provide you with a free treatment to re-dose your vehicle at no additional cost. This is our guarantee to you.