10 Best Radiator Sealants 2020

Gareth Otwell Reviewed by Gareth Otwell | Last Updated:

After analyzing products, scanning reviews, spending more than 36 hours of research and speaking with our test users, we think the Product Name: K-Seal ST5501 Multi Purpose One Step Permanent Coolant is the one of the Best Radiator Sealant on the market.

Product Name: K-Seal ST5501 Multi Purpose One Step Permanent Coolant – Best Overall Radiator Sealant

Product Name: K-Seal ST5501 Multi Purpose One Step Permanent Coolant
  • REPAIRS IN MINUTES: Formulated to permanently weld radiators, including hard plastic aluminum heads and blocks in old and new cars. The only car radiator and gasket sealant university tested to meet ASTM D3147. Save time/money. US Bestseller
  • SEALS CRACKS AND STOPS LEAKS: A DIY alternative to costly repairs, our coolant leak fix permanently seals cracks and holes! It quickly repairs your leaking radiator, freeze plug, heater core and water pump casing with no adverse impact on efficiency.
  • POUR AND GO: Our cooling system sealer is easy to use: just shake the bottle, add to your radiator/overflow and run the engine! Unlike some traditional products, it mixes with all types of antifreeze, absolutely no draining or flushing required.
  • SCIENTIFICALLY TESTED: Safe and effective, our cracked block repair can seal leaks up to 1/32 of an inch! Once cured, the repair withstands the high pressure of the combustion chamber, all without failing or clogging the cooling system.
  • CUSTOMER SUPPORT: If our engine coolant leak doesn't seal your head gasket, the system might be over-pressurized. Check the Technical Specification section of this page for extra instructions for a successful repair. Over 8 million bottles sold.

Bar's Leaks Liquid Aluminum Stop Leak

Bar's Leaks Liquid Aluminum Stop Leak
  • Bar's Leaks Liquid Aluminum Stop Leak seals radiator leaks. Seals freeze plug leaks. Repairs gasket leaks and heater core leaks. Lowers water temperature.
  • Seals radiator leaks
  • Seals freeze plug leaks
  • Repairs gasket leaks
  • Special Shipping Information: This item cannot be returned and has additional shipping restrictions

Permatex 82180 Ultra Black Maximum Oil Resistance RTV Silicone Gasket

Permatex 82180 Ultra Black Maximum Oil Resistance RTV Silicone Gasket
  • Sensor-safe, non-corrosive formula designed for superior adhesion to oily surfaces and long term durability
  • Superior resistance to powertrain fluids including engine oil, transmission fluid, gear lube and coolants
  • Retains high flexibility and eliminates the need for pre-formed, pre-cut, paper, rubber or cork gaskets; OEM specified and approved for dealership warranty requirements
  • Temperature Range -65°F to 500°F (-54°C to 260°C) intermittent
  • Suggested Applications: Valve covers, oil pans, intake manifold end seals, timing covers, and differential covers
  • Fit Type: Universal

ATP AT-205 Re-Seal Stops Leaks

ATP AT-205 Re-Seal Stops Leaks
  • Professional strength fast acting resealer, stops leaks fast
  • Rejuivinates all rubber seals & gaskets in engines, transmissions, power steering, differentials and hydraulic systems
  • Compatible with conventional and synthetic oils, ATF, gear oil, power steering fluids and hydraulic oil
  • Does not contain petroleum distillates, will not over-swell or breakdown seals
  • 8oz bottle will treat a 6 quart capacity, adjust accordingly

Bar's Leaks HDC Radiator Stop Leak Tablet – Best Budget Radiator Sealant

Bar's Leaks HDC Radiator Stop Leak Tablet
  • Seals leaks
  • Conditions cooling system
  • Inhibits rust and corrosion
  • Lubricates water pump seals
  • Helps control electrolysis

J-B Weld 2120 Radiator and Plastic Repair Kit – Premium Pick

J-B Weld 2120 Radiator and Plastic Repair Kit
  • RADIATORWELD: Our radiator and plastic tank repair kit has all you need for making professional quality, permanent repairs with state of the art components and easy to follow instructions.
  • COUNT ON US: For more than 40 years, our products have earned a loyal following from people who take pride in their work. With each product we innovate, we continue to provide the world's strongest bond for your projects.
  • SIMPLE TO USE: No removal of tank or radiator is required to stop leaks. Easily fix holes up to 3/8" diam. or cracks up to 4" long. Includes epoxy putty, fiberglass cloth, sandpaper, and applicator.
  • VERSATILE & DEPENDABLE: Great for radiators, washer fluid tanks, storage tanks, water tanks, plastics, composites, PVC and more. Professionals, mechanics and avid DIYers know J-B gets the job done.
  • NO PROJECT TOO BIG OR TOO SMALL: We have all the products you need to get the job done right. JB Weld always delivers the legendary performance of the World's Strongest Bond.

AlumAseal ASBPI12 Radiator Stop Leak Powder Blister Card

AlumAseal ASBPI12 Radiator Stop Leak Powder Blister Card
  • Stops leaks safely, quickly and easily
  • Safe and effective for all metal, plastic and rubber cooling system parts
  • Will not clog cooling systems
  • Compatible with all antifreeze and coolants
  • Stop leak tube treats cooling systems up to 22 quarts (21 liters)

Prestone AS195 Complete Care and Stop Leak

Prestone AS195 Complete Care and Stop Leak
  • Extends and protects water pump life
  • Formulated with patented Grafted Polymer Technology
  • Reduces friction and protects against corrosion
  • Helps in just 1 treatment
  • Also stops and prevents leaks in all major cooling system components

Genuine GM (12378255) Fluid 3634621 Cooling System Seal Tablet

Genuine GM (12378255) Fluid 3634621 Cooling System Seal Tablet
  • Non-toxic
  • DEX-COOL compatible
  • Engine application is based on liters of volume in cooling system
  • Formulated for automotive use
  • For use with all vehicles

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