Your Radweld FAQs Answered

Over time, deposits, dust and general wear and tear can cause leaks to develop in a car’s radiator, with the main symptoms including leaking coolant/antifreeze and an overheating engine. In the past, this would have meant a pricey repair bill, but thanks to Holts Radweld, fixing a leaky radiator is now a job you can do yourself at home.

If you suspect your car’s radiator is leaking, Radweld provides a simple means of repair. Find out more about how the product works and how to use it in our FAQs below.

Is Radweld a permanent repair?

Yes, Radweld provides a permanent repair for small cracks, holes, and leaks in your car’s radiator. The solution provides a permanent, water-tight seal, so you can get back on the road without worrying about further breakdowns or expensive repair bills.

How Does Radweld work to fix a radiator leak?

If you’re looking for a quick, easy, and cost-effective solution to a leaky radiator, look no further than Radweld. It’s one of our most popular products, and drivers have been using it for decades to repair leaks in radiators.

Radweld works its way through the system, seeking out leaks and forming permanent repairs in minutes. Radweld has been carefully formulated to mix with all engine coolant and antifreeze types, and works quickly to fill small holes and gaps, resealing the system to permanently repair leaks.

Radweld can be poured directly into the cooling system, with no need to drain or flush the system first. The product also provides anti-corrosion protection and prevents future leaks; it will last the lifetime of the coolant in the system.

Will Radweld clog the system?

No, Radweld has been developed to ensure that it never blocks the channels in a car’s radiators.

The product is safe to use in all cars, cooling systems, and alongside any brand of coolant/antifreeze. It’s guaranteed to not cause clogging in the system, so you can use it with confidence to repair small holes and leaks.

How do I use Radweld to fix a radiator leak?

Radweld is designed to be added directly into the engine’s expansion tank. You don’t need to drain or flush the system before you use it – just pour and go. Radweld works through the radiator channels to seal leaks without any clogging or damaging effects, so all you need to do is pour it in and let it repair the leak.

When adding Radweld, it’s important to ensure the engine has cooled before unscrewing the cap of the expansion tank as the coolant operates at around 90°C. After filling with Radweld, make sure that the cap of the expansion tank is replaced and tightened.

This video shows you how to use Radweld and what happens in your radiator after you’ve used it.

How to use Radweld – Simply pour and fix 

  1. We recommend you let the engine cool before use.
  2. Remove the cooling system cap.
  3. Shake the Radweld bottle and pour into the cooling system.
  4. Run your car’s engine for 15-25 minutes with the heater on and check to see that the leaking has stopped.
  5. Finally check your car’s coolant level. If it’s less than the level recommended by your vehicle’s handbook then top it up as needed.
  6. For more extensive leaks, consider using Radweld Plus or Wondarweld.

Can I use Radweld before an MOT?

Yes, you can use Holts Radweld before an MOT. A leaking radiator can be expensive to repair, and could cause your car to fail its MOT, so solving the problem at home first can be an ideal solution.

An MOT inspection is a thorough test of your vehicle’s roadworthiness, so if there are other problems with your vehicle, the MOT tester may still recommend additional work is carried out before it is passed. Using Radweld doesn’t guarantee your car will pass the MOT, but it will quickly and permanently repair leaks and help you to avoid costly radiator repairs.

Can I use Radweld if my car is under warranty?

We would advise checking with the provider of your warranty before attempting a repair of any type. Like all of the Holts long-term or permanent repair products, it is important to check the details of your warranty before you use them in case you risk invalidating it.

Holts Radweld is a safe and permanent way to repair your car’s radiator in minutes. Holts Radweld is designed to cause no damage and can be used without flushing the cooling system, making it easy to use on your driveway.

If your car is still under warranty, however, you should check the details and work out the best option for you before you use Radweld.

If I use Radweld will I have to replace my radiator later?

Radweld permanently fixes leaks without damaging your radiator, so you can simply pour and go, and feel confident that your radiator is fixed and free from leaks. While Radweld has anti-corrosive properties, we can’t guarantee that your radiator will never need replacing, as there could be unrelated problems further down the line.

For more information on our DIY car maintenance range, click here, or get in touch with our experts if you need further help and advice.