Best Head Gasket Sealers UK (Reviews) 2021

Best Head Gasket Sealer UK

Head gasket sealers can save you a lot of time and money. If you have a blown head gasket, then rather than have a mechanic take your engine to pieces to remove and replace it, you can pour a special sealant fluid into the cooling system, hopefully repairing and fixing any leaks that are occurring.

Older vehicles with higher mileage on the clock are more prone to having head gasket failure, so having a small bottle of sealant available is good practice in case of an emergency. Typically a good sealer will permanently fix any engine gasket leaks that you have, though some will cause more damage than good. We listed our 5 top sealers for head gaskets that you should consider when shopping for a solution to a blown gasket, without the need to splash out on a mechanic.

Best Head Gasket Sealers in the UK Reviews

#1. KALIMEX LTD KSEAL Coolant Leak Repair

KALIMEX LTD KSEAL Coolant Leak Repair

Currently, one of the most popular options for fixing your blown gasket at home is this bottle of KALIMEX LTD KSEAL. Though it may look simple, this bottle is filled with a specialized liquid that, when poured into the engine properly, it can permanently fix gasket head leaks upto 0.635mm in size. In fact, most cars, SUVs, and small trucks only need one 263 ml bottle of this stuff to get their engine make up to par.

This option’s leak-stopping capabilities derive from its use of K-Seal Ultimate, a proprietary formula used by this brand that incorporates micro-fibres into the leak repair process. This formula also mixes harmoniously with all types of coolant and antifreeze, thus ensuring that your engine is free of any clogs that could otherwise cause it to lose functionality again.


  • One 263 ml bottle is enough to fix gaskets in most cars, SUVs, and small trucks
  • K-Seal Ultimate formula uses ceramic micro-fibres to seal cracks as small as 0.635mm
  • Mixes with all types of coolant or antifreeze


  • A little on the expensive side, per bottle

#2. Holts Radweld Plus

Holts Radweld Plus

Another popular option is this bottle of Holts Radweld Plus Coolant Leak Repair. DIYers in particular favour this head gasket sealer option because it utilizes a one-step “pour-and-go” application process. Holts Radweld Plus even cures within minutes, which is a major improvement over a formerly hours-long finishing process. So long as you follow the volume instructions on the bottle, even novice at-home mechanics will be able to return their engine to working order with Holt Radweld Plus.

While Holts doesn’t go into detail on the contents of their formula, they do indicate that it has been recently reengineered to prevent clogs from forming when the liquid interacts with coolant. This used to be a major reason to avoid DIY head gasket sealers, so it is nice to see that Holts has redoubled their effort to make clog prevention an industry standard going forward.


  • One-step “pour-and-go” application process
  • Cures in minutes without the need to drain or flush the system
  • Formulated to prevent clogs


  • Unclear how much volume is needed for large vehicles

#3. Steel Seal Blown Cylinder Head Gasket Sealer

Steel Seal Blown Cylinder Head Gasket Sealer

Next up, let’s have a look at Steel Seal’s Blown Cylinder Head Gasket Sealer. This option considered one of the best values in this collection, especially for UK-based shopper. That’s because this head gasket sealing liquid can be shipped in the UK for free, making this a reasonably affordably option compared to marked-up retail prices. Chances are, you’ll only need one 473 litre bottle as well due to this sealer’s reliability (after proper application and curing, that is).

In terms of its productivity, Steel Seal is up there with the best options in this collection when it comes to forming a reliable seal on a cracked gasket. In fact, so long as your motorbike, van, pickup, 4x4, tractor, or boat uses standard architecture, you can count on this liquid sealer to immediately relieve the symptoms of a blown gasket. That includes if your car, etc., uses a water cooling system, as this liquid is fully compatible with those (as well as most common antifreeze liquids).


  • 2.5 litre engines only require one 473 litre bottle
  • Also works for bikes, vans, pickups, 4x4s, tractors, and boats
  • Compatible with all types of antifreeze


  • Prices vary based upon the provider
  • Requires more heat than average to properly cure

#4. Hi-Gear HG9048s Insta-Seal Fix

Hi-Gear HG9048s Insta-Seal Fix

Hi-Gear HG9048s Insta-Seal Permanent Block Sealer is for the committed DIY mechanic who wants to get serious about resolving a nagging head gasket problem. That’s because Hi-Gear HG9048s permanently seals large and small leaks in blown head gaskets by way of its proprietary Insta-Seal formula. This specialized mix of liquids can work on aluminium and cast iron engines alike, as well as cylinder heads, heater matrix, core plugs and radiators.

Right off the bat, you might be wondering how Hi-Gear HG9048s manages to do so much with only 236 ml of liquid per bottle. As it turns out, this head gasket sealer’s formula includes ceramic and copper micro-fibres, which weave together at the sight of the leak to create an impenetrable bond. Even as your engine’s metals expand at over 200° C, you can count on this “weld” to hold firm and prevent another blown gasket.


  • Works on cracked cylinder heads, heater matrix, core plugs, and leaking radiators
  • Compatible with all aluminium and cast iron engines
  • Insta-Seal formula includes ceramic micro-fibres and copper fines for quick, durable seals
  • Expands and contracts at temperatures up to 200° C


  • May need multiple bottles for larger engines

#5. HYPER-SEAL Repair Liquid

HYPER-SEAL Repair Liquid

While it may not have the name recognition of some of these larger name brands, HYPER-SEAL Head Gasket Repair Liquid is also a gasket repair option that you should take into full consideration. This is especially the case if you own a vehicle from a high-end brand such as BMW, Range Rover, Vauxhalls, Fiats, Renaults, or Peugeots. HYPER-SEAL has created their “Seals as Steel” formula to prioritize the care of these valuable engines by way of a permanent molecular bond directly on the vehicle’s existing gasket.

Though it takes 20 minutes for HYPER-SEAL to cure, you can count on it to remain reliable on cast iron and aluminium engine blocks with the same level of certainty. HYPER-SEAL even went so far as to have their formula tested by Amalgatech Laboratories, an American firm that has vouched for the liquids overall ability to reseal gaskets without the need for further professional interventions.


  • Seals leaks in radiators, core plugs, heater matrix, water pumps, and thermostat gaskets
  • Formulated to work best with BMWs, Range Rovers, Vauxhalls, Fiats, Renaults, and Peugeots
  • Formula tested at Amalgatech Laboratories to ensure reliability
  • Cures in only 20 minutes


  • Expensive, per bottle
  • Difficult to pour in due to opening shape

Sealer for Head Gaskets Buying Considerations

Can You Do This on Your Own?

As with all types of home auto repair, you should evaluate your own capacity to accomplish the task at hand before initiating it. This is particularly the case when it comes to repairing a gasket, which interacts with several extremely important components of your vehicle’s engine. Any mistakes made during the gasket sealing process could leave your car permeant incapacitated, so it is best to read up on the proper procedure before even purchasing any liquid sealer.

Get Enough Liquid to Finish the Job

One of the single biggest mistakes you could make during the gasket resealing process is failing to apply enough liquid to satisfactorily seal your vehicle’s entire gasket. Doing so will cause the new seal to fail almost immediately, which exposes your vehicle (and your engine, specifically) to further harm. As such, before you begin pouring in any sealant liquids, be sure to carefully read your product’s instructions to ensure that you have enough liquid based upon the size of your vehicle’s engine (often in litres).

The Final Word

For a much cheaper cost than having to get your head gasket removed and repaired by a mechanic, you can at least try a bottle of sealant to try and fix the leak permanently first. Sealants might not work in every scenario, and it might be the case you may have to replace the head gasket completely. We recommend you start with whatever pick from our best head gasket sealer list above that ticks the boxes for your car and go from there.

Last Updated On: April 10, 2021.

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