Cylinder Block Seal

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Repairs cracks in cylinder blocks in 30 minutes without dismantling. Repairs cracks and leaks in head gaskets (metal only). High pressure and vibration resistant.

Case size: 1 x 325ml
Case size: 12 x 325ml

For case pricing, please use  Request a Quote 

Key Benefits

  • Forms a glass hard layer when exposed to air
  • Repairs cracks in cylinder blocks of cast iron, steel and aluminium, without dismantling
  • Stops small leaks/cracks in metal head gaskets
  • Assures a permanent repair in 30 minutes
  • Resists high pressures, water pressure and vibration
  • Does not clog hoses
  • Does not repair rubber gaskets


  • Internal and external cracks in cylinder blocks, which lead to external or internal water loss to the oil system or combustion chamber
  • In case of severe white exhaust smoke
  • In case of coffee coloured oil/water emulsion in the oil system (can be seen on filler cap)

Directions for use

Normal treatment: Replace old liquid by water. Add Wynn’s Radiator Flush to the water. Let the engine run for 15 min. Drain this mixture and rinse with water. Refill system with water. Remove the upper radiator hose and the thermostat. Shake the bottle of Wynn’s Cylinder Block Seal before use. In cold temperatures, warm the bottle. Pour Wynn’s Cylinder Block Seal into the opening of the removed thermostat (325 ml treats circuits up to 8 litres). Replace the dismantled parts to close cooling system again (thermostat is NOT replaced). Top up liquid level with water. Warm up engine. After warm-up let the engine run for at least 15 to 20 minutes. Check water temperature during treatment. Stop the engine. Drain when engine is cold and flush completely. Fill with cooling liquid (antifreeze + water). Replace thermostat. 

Cracks in cylinder wall: Proceed in the same way, but remove the spark plug (petrol) or injector (diesel) from the damaged cylinder. When several cylinders are damaged, remove the spark plugs (injectors) sequentially, leaving each one out for 5 minutes. 

For large cracks: Proceed in the same way, but leave Wynn’s Cylinder Block Seal in the cooling system for 3 to 4 days, before draining. 

  • If the product is spilled on glass or paint, remove immediately with clean water
  • Use Wynn’s Radiator Stop Leak to prevent and stop leaks in the radiator
  • Wynn's Cylinder Block Seal is not compatible with cooling liquids. It should only be added to water. Do not our it into oil or directly into the cylinders
Product code 496
Case size 12 x 325ml
Physical state Liquid
Density @20°C -
Colour -
Flash point -
Odour Characteristic
Barcode 6001296004967
MSDS: Download PDF
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