Holts Wondarweld 250ml

Holts Wondarweld 250ml is a cooling system treatment from Holts, supplied in a 250ml pack, used for flushing, cleaning or sealing the cooling system.

Holts Wondarweld is a professional cooling system repair product that’s designed to fix small cracks and holes in the cylinder head, engine block and head gasket. Thanks to its heavy-duty formula, the product provides a permanent repair without causing damage or clogging the system, so you can fix small problems without the need for a costly repair.

How Does Wondarweld Work?

Wondarweld is a professional, heavy-duty repair solution that’s suitable for all engine types. Added direct to the cylinder head, it permanently seals small holes and cracks in the engine block, head gaskets and water pump gaskets, restoring the integrity of the engine and cooling system.

Once added to the engine, Wondarweld circulates through the cooling system, seeking out small holes, cracks, and leaks to form a permanent repair. Lab-developed to ensure maximum performance and longevity, the product is safe for use on all common engine materials, including steel, aluminium, and iron.

A 250 ml bottle of Wondarweld is sufficient for cooling systems up to 8-litre.

How Do I Use Wondarweld?

Before using Wondarweld, drain the cooling system and flush with Cooling System Flush to remove any residue and contaminants left behind by the old coolant. After draining, reattach the bottom hose.

To use Wondarweld, you’ll need to remove the top hose from the cylinder head outlet before removing the thermostat. Do this, then use a funnel to apply the product directly into the cylinder head outlet, taking care not to pour into oil as this can cause serious engine damage.

After applying the product, replace the thermostat and top hose. Refill the system with clean water and run the engine for 15 minutes to repair the leak.

When the repair is complete and no fluid is leaking, drain the system again, flush with clean water, and then top up with a high-quality coolant/antifreeze product.

Do I Have to Remove the Engine Thermostat to Use Wondarweld?

Yes. Since Wondarweld is designed to be applied directly to the cylinder head outlet, you’ll need to remove the top hose and thermostat to access it. After pouring the product into the system, you can replace the thermostat and hose before circulating the product through the system.

Does Wondarweld Offer a Permanent Repair?

Holts Wondarweld is designed to provide a permanent repair for small holes and cracks in engine blocks, cylinder head gaskets and water pump gaskets. Tested to the highest standards, it is used by professionals to fix cooling system leaks without the need for other more time and labour-intensive means of repair.

Specifications at a glance

Supplied sealed in the manufacturer's original packaging and dispatched from the UK by Nitroma Lubricants. Always read the label and follow the manufacturer's directions and safety advice before use.