Top 10 Coolant Stop Leaks (April 2024)

K-SEAL Coolant Leak Repair – ⭐ Best Overall Coolant Stop Leak

ST5501 by K-Seal

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 K-Seal engine coolant leak stop doesn’t seal, 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 worldwide!

1186 by Bar's Leaks

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

ST5516 by K-Seal

REPAIRS IN MINUTES: Create a permanent weld within the entire coolant system, including on hard plastic radiators and aluminum heads and blocks in larger capacity engines, AG, RV etc. The only industrial coolant sealant university tested to meet ASTM D3147.
SEALS CRACKS AND STOPS LEAKS: Avoid expensive downtime, our coolant stop leak will permanently seal cracks and holes! Quickly repair your head gasket, block, leaking radiator, freeze plug, heater core & 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 competitive products, it mixes with all types of antifreeze, no draining, flushing or pulling the thermostat required.
SCIENTIFICALLY TESTED: Safe and effective, our Heavy Duty Coolant stop leak repair seals leaks up to 1/32 of an inch! Once cured, it withstands the high pressure of the combustion chamber, without failing or clogging the cooling system. US Bestseller
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. Save time/money

PLT11 by Bar's Leaks

1150 by Bar's Leaks

Stops cooling system leaks
Compatible with all brands of anti-freeze including conventional green or blue and extended life red/orange or yellow (OAT/HOAT) coolant
Premium carbon fiber formulation for extended protection

20132 by Liqui Moly

LIQUI MOLY Radiator Stop-Leak completely seals such leaks immediately with ease.
Secures the combustion chamber from damages caused by coolant admission
For all cooling water and heating systems with and without water filters

1196 by Bar's Leaks

00211 by Blue Devil

DS-114 by J-B Weld

JB WELD PERM O SEAL : Is a specially formulated non-toxic compound ground to a very fine particle size to quickly mix and flow into all areas of the cooling system to find and seal leaks.
WHAT THE PROS USE: Mechanics, repair pros, and any avid DIYer knows our products bond strong to a variety of surfaces in even the toughest environments; and they have always been made in the USA.
MONEY SAVING REPAIR SOLUTION: The powered concentrate allows for an economical repair as compared to liquid based alternatives that use similar technology.
DURABLE FAST FIX: The special compound will quickly seal leaks and will also act as a rust inhibitor and lubricant to internal cooling system parts. It will not clog or harm your cooling system.
DO IT YOURSELF: Big or small, you can DIY it with J-B. Our heavy duty adhesives repair & restore it right the first time. JB Weld delivers the legendary performance of the World's Strongest Bond.

XA 40913 by XADO

Eliminates The Need For Expensive Repair
Universal Application For Gasoline And Diesel Engines Of Automobiles And Other Equipment
Neutral For Materials Of Cooling System Parts (Gaskets, Rubber Hoses, Aluminum, Plastic And Steel Radiators)
Provides A Long-term Protection Of The Cooling System Against Rust And Corrosion
Best Leaking Radiator Repair Additive