Miracle Seal permanently seals small leaks in radiators, hose pipes, water pumps and even hairline cracks in engine blocks. Compatible with all water-based coolants and antifreeze. Non-clogging formula with built-in anti-corrosion and lubricating additives. One bottle treats up to 25 litres of coolant.
Size
Price
QTY
Each
£10.95£13.14£8.45£10.14
BO x 12 - £8.25 EACH
£99.00£118.80
Miracle Seal is a cooling system leak sealer developed for fast emergency repairs when you cannot afford downtime. Whether it is a weeping radiator, a seeping hose connection, a leaking water pump, or even a hairline crack in a head gasket or engine block, pour this in and get the engine running again. One 250ml bottle is sufficient for up to 25 litres of coolant, which covers most passenger vehicles and light commercial engines in a single application.
The formula is water-based, which matters. It carries a suspension of soft, non-clogging particles that are small enough to circulate freely through the entire system without blocking narrow coolant passages or interfering with the thermostat, water pump impeller or heater matrix. That last point causes a fair amount of anxiety when people reach for a stop-leak product, and rightly so, because some older products on the market genuinely will bung things up. Miracle Seal will not. The particles only consolidate and seal at the point where coolant is escaping, which is exactly where you want them.
Where Miracle Seal Works in the Cooling System
Beyond the immediate repair, Miracle Seal also contains anti-corrosion additives that help protect metal surfaces within the cooling circuit, and lubrication additives that reduce wear on the water pump seal. It is fully compatible with all water-based coolants and will continue working even in systems running antifreeze, which is most of them for the better part of the year in the UK.
For minor leaks, the repair is often permanent. For more significant damage, Miracle Seal buys time to get a vehicle to a workshop without losing the entire coolant charge on the way. In both cases it is far cheaper than a tow. It works in metal and plastic radiators, and the instructions are straightforward enough that it can be added roadside if needed, provided the engine has warmed up first.
Pro Tip: Always run the engine for at least five minutes after adding Miracle Seal so the product circulates fully and reaches operating temperature, otherwise the particles will not seat properly at the leak point.
Miracle Seal is used across passenger cars, vans, light commercials and agricultural machinery anywhere a coolant leak has developed and a full mechanical repair is not immediately possible. It is commonly used on leaking metal and plastic radiators, leaking water pump housings, seeping hose unions and hairline cracks in cylinder head gaskets or engine blocks. Fleet operators and breakdown recovery professionals keep it on the van as a reliable first-response fix. It is equally useful for a private vehicle owner who needs to get home without calling a recovery truck.
Best For
Leaking radiators (metal and plastic)
Water pump seal leaks
Hose pipe connections
Hairline cracks in head gaskets
Hairline cracks in engine blocks
Emergency roadside repairs
Fleet maintenance first response
Compatible With
All water-based coolants
Antifreeze mixtures
Metal radiators
Plastic radiators
Petrol and diesel engines
Cars, vans and light commercials
Key Properties
Non-clogging particle suspension
Anti-corrosion additives
Lubrication additives
Permanent seal on minor leaks
250ml treats up to 25 litres of coolant
Water-based formula
Not suitable for: Not intended for large structural coolant leaks or heavily corroded systems where significant material has failed. It is a sealant for small leaks and hairline cracks, not a substitute for mechanical repair of burst hoses, cracked radiator tanks or badly damaged head gaskets.
Miracle Seal is poured directly into the radiator filler with the engine warm and the heater valve open. The key is getting the product circulating through the whole system, including the heater matrix, before the engine is switched off. On older vehicles with heavy scale or rust in the cooling circuit, flushing the system first will give better results and ensure the product reaches the leak site cleanly.
Once added, run the engine for at least five minutes at normal operating temperature. The non-clogging particles will circulate freely and deposit only where coolant is escaping, forming a seal as the leak point dries. Top up the coolant to the correct level once the engine has cooled. For minor leaks, no further treatment is required.
Flush out heavily scaled or dirty cooling systems before use for best results.
Open the heater valve fully and switch the cabin heating on.
Run the engine until it reaches normal operating temperature.
Shake the bottle of Miracle Seal thoroughly before opening.
Pour the entire contents into the radiator filler.
Replace the radiator cap and run the engine for at least five minutes.
Allow the engine to cool completely, then top up the coolant to the correct level.
Will Miracle Seal block my heater matrix or thermostat?
No. The formula uses soft, non-clogging particles that are specifically designed to circulate freely through narrow coolant passages. They only consolidate at the point where coolant is escaping. This is the key difference from older stop-leak products, which used fibrous or granular materials that could restrict flow.
Can I use Miracle Seal if my coolant already contains antifreeze?
Yes. Miracle Seal is fully compatible with antifreeze and will continue to work and hold the seal in a mixed coolant system. There is no need to drain and refill with plain water first.
How long does one bottle last, and is the repair permanent?
One 250ml bottle treats up to 25 litres of coolant, which is sufficient for most cars and light vans in a single application. For minor leaks and hairline cracks, the repair is often permanent. Larger or more heavily damaged areas may require mechanical repair, but Miracle Seal will hold well enough to get you to a workshop safely.
Miracle Seal is a water-based suspension of soft, non-clogging particles combined with anti-corrosion and lubricating additives. The particles are sized to pass freely through radiator cores, heater matrices and water pump housings without causing restriction, and consolidate only where there is fluid loss. The anti-corrosion chemistry helps protect ferrous and aluminium surfaces within the cooling circuit, while the lubricating additives reduce wear on water pump seals. One 250ml canister is formulated to treat cooling systems of up to 25 litres capacity.
Volume
250ml
Treats up to
25 litres of coolant
Formula type
Water-based particle suspension
Antifreeze compatible
Yes
Clogging risk
Non-clogging
Additives
Anti-corrosion, lubricating
Packaging
Non-compressed canister
Size
Each, BO x 12 – £8.25 EACH
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