Avoid costly repair bills and downtime with K-Seal HD K5516 Coolant Leak Repair; the simple, permanent solution to cooling system leaks. K-Seal HD fixes most leaks in water-cooled engines and is designed specifically for HGVs, tractors, heavy plant and other commercial vehicles. It is compatible with all coolant system additives and kinds of antifreeze, meaning you can use K-Seal HD with confidence at all times. With K-Seal HD there’s no need to take a commercial vehicle off the road – just apply and run the engine as normal. K-Seal HD’s scientifically-tested formula, containing ceramic microfibers and copper particles, will seek out cracks and holes and provide a guaranteed repair for the lifetime of the engine.