10 Best Stop Leaks For Radiator
for June 2021

Recommendations are independently chosen by MOOZ’s editors. Purchases you make through our links may earn us a commission.

1
9.7
SCORE
K-SEAL Coolant Leak Repair, ST5501 8oz, Multi-Purpose Formula Stops Leaks in the Radiator, Head Gasket, Block, Water Pump Casing, Heater Core, and Freeze Plug - Pour and Go - Trade Trusted-Stop Leak

K-SEAL Coolant Leak Repair, ST5501 8oz, Multi-Purpose Formula Stops Leaks in the Radiator, Head Gasket, Block, Water Pump Casing, Heater Core, and Freeze Plug

Pour and Go, Trade Trusted-Stop Leak

by K-Seal
What We like

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.

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Product Features

  • 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
  • CUSTOMER SUPPORT: If K-Seal engine coolant leak stop doesnt 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!
  • 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.
  • 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.

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. Customer support: if K-Seal engine coolant leak stop doesnt 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! 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. 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

2
9.5
SCORE
Bar's Leaks PLT11 Pelletized HD Radiator Stop Leak - 11 oz.

Bar's Leaks PLT11 Pelletized HD Radiator Stop Leak

11 oz.

by Bar's Leaks
What We like

Helps control electrolysis

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Product Features

  • Lubricates water pump seals
  • Conditions cooling system
  • Inhibits rust and corrosion
  • Seals leaks

Conditions cooling system Seals leaks Inhibits rust and corrosion Lubricates water pump seals

3
9.5
SCORE
K-SEAL Coolant Leak Repair ST5516 Heavy Duty 16oz, Multi-Purpose Formula for Truck/Tractor Coolant Leaks in the Radiator, Head Gasket, Water Pump Casing & Heater Core, A True Pour & Go -Trade Trusted

K-SEAL Coolant Leak Repair ST5516 Heavy Duty 16oz

Multi-Purpose Formula for Truck/Tractor Coolant Leaks in the Radiator, Head Gasket, Water Pump Casing & Heater Core, A True Pour & Go -Trade Trusted

by K-Seal
What We like

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

more infoarrow_drop_down

Product Features

  • 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.
  • CUSTOMER SUPPORT: If our engine coolant leak doesnt 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
  • 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.

Customer support: if our engine coolant leak doesnt 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 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. 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. 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.

4
9.5
SCORE
K-SEAL Ultimate Permanent Head Gasket Repair ST3501 16oz Multi-Purpose Formula Stop Leaks in the Head Gasket, Cracked/Porous Blocks, Radiator & Heater Core. A True Pour & Go, Trade Trusted Stop Leak

K-SEAL Ultimate Permanent Head Gasket Repair ST3501 16oz Multi-Purpose Formula Stop Leaks in the Head Gasket

Cracked/Porous Blocks, Radiator & Heater Core. A True Pour & Go, Trade Trusted Stop Leak

by K-Seal
What We like

SCIENTIFICALLY TESTED: Safe, effective, our head gasket and block repair seals 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. US Bestseller

more infoarrow_drop_down

Product Features

  • CUSTOMER SUPPORT: If our head gasket repair leak doesnt seal your intake 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.
  • SEALS CRACKS AND STOPS LEAKS: A DIY alternative to costly repairs, our head gasket fix permanently seals cracks and holes! Quickly repair your blocks, leaking radiator, freeze plug, heater core and water pump casing with no adverse impact on efficiency.
  • POUR AND GO: Our head gasket sealer is easy to use just shake, add to your radiator/overflow and run the engine! Unlike some competitive products, it mixes with all types of antifreeze, absolutely no draining, flushing or pulling the thermostat required.
  • REPAIRS IN MINUTES: Permanently fix blown head gaskets, cracked heads and cracked/porous blocks including aluminum heads in old and new cars. The only head gasket and block sealant that is 3rd party tested to meet ASTM D3147. Save time/money

Customer support: if our head gasket repair leak doesnt seal your intake 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. Pour and go: our head gasket sealer is easy to use just shake, add to your radiator/overflow and run the engine! unlike some competitive products, it mixes with all types of antifreeze, absolutely no draining, flushing or pulling the thermostat required. Seals cracks and stops leaks: a diy alternative to costly repairs, our head gasket fix permanently seals cracks and holes! quickly repair your blocks, leaking radiator, freeze plug, heater core and water pump casing with no adverse impact on efficiency. Repairs in minutes: permanently fix blown head gaskets, cracked heads and cracked/porous blocks including aluminum heads in old and new cars. the only head gasket and block sealant that is 3rd party tested to meet astm d3147. save time/money

5
8.9
SCORE
Prestone AS145 Radiator Sealer Stop Leak - 11 oz.

Prestone AS145 Radiator Sealer Stop Leak

11 oz.

by Prestone
What We like

Combination of natural and synthetic components provides the ability to seal leaks up to 0.020" x 0.5"

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Product Features

  • Patented formula quickly stops leaks in radiators, water pumps, and heater cores
  • Seals even large leaks without interfering with the flow through the radiator or heater core
  • Boosts corrosion inhibitors to protect against pitting and corrosion, which cause radiator leaks
  • Stops the leak as well as the corrosive condition that causes it

Boosts corrosion inhibitors to protect against pitting and corrosion, which cause radiator leaks Seals even large leaks without interfering with the flow through the radiator or heater core Patented formula quickly stops leaks in radiators, water pumps, and heater cores Stops the leak as well as the corrosive condition that causes it

6
8.8
SCORE
Dike Temporary Radiator Stop Leak

Conklin Dike Temporary Radiator Stop Leak Dike Temporary Radiator Stop Leak

by Conklin
What We like

works with all standard and permanent antifreezes

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Product Features

  • Stops leaks in radiators in seconds
  • Seals internal leaks, preventing antifreeze and water from seeping into engine
  • Helps gaskets seal better
  • Will not block small passages in coolant system

Helps gaskets seal better Seals internal leaks, preventing antifreeze and water from seeping into engine Stops leaks in radiators in seconds Will not block small passages in coolant system

7
7.9
SCORE
DS-114 PERM-O-SEAL Radiator Stop Leak - 0.7 oz, Pack of 2

J-B Weld DS-114 PERM-O-SEAL Radiator Stop Leak

0.7 oz, Pack of 2

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8
7
SCORE
Bar's Leaks 1109 Block Seal Liquid Copper Intake and Radiator Stop Leak - 18 oz.

Bar's Leaks 1109 Block Seal Liquid Copper Intake and Radiator Stop Leak

18 oz.

by Bar's Leaks
What We like

Repairs blocks

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Product Features

  • Repairs freeze plug leaks
  • Repairs heater core leaks
  • Repairs blown head gaskets
  • Seals larger leaks seals

Seals larger leaks seals Repairs freeze plug leaks Repairs heater core leaks Repairs blown head gaskets

9
7
SCORE
C and R Racing Radiators 59-00001 Dike Stop Leak, 1 Pack

C and R Racing Radiators 59-00001 Dike Stop Leak

1 Pack

by C and R Racing Radiators
What We like

Package Weight : 1.2 pounds

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Product Features

  • Can prevent a DNF in the event of a radiator puncture, cracked cylinder head, or head gasket Problem
  • After extensive research, C & R racing has found a stop leak that doesn't leave a residue
  • C&R Stop Leak stays suspended in the water so that when the water is drained, all of the stop leak is drained with the water leaving no residue

C&r stop leak stays suspended in the water so that when the water is drained, all of the stop leak is drained with the water leaving no residue Can prevent a dnf in the event of a radiator puncture, cracked cylinder head, or head gasket problem After extensive research, c & r racing has found a stop leak that doesn't leave a residue

10
7
SCORE
AlumAseal ASLC16 Radiator Stop Leak and Conditioner Liquid - 16 Fl oz.

AlumAseal ASLC16 Radiator Stop Leak and Conditioner Liquid

16 Fl oz.

by Gold Eagle Co.
What We like

Safe and effective for all metal, plastic and rubber cooling system parts

more infoarrow_drop_down

Product Features

  • Compatible with all antifreeze and coolants
  • Stops leaks safely, quickly and easily
  • Lubricates water pump

Stops leaks safely, quickly and easily Lubricates water pump Compatible with all antifreeze and coolants

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