J-B Weld 2120 Radiator Repair Kit

J-B Weld 2120 Radiator Repair Kit is a ready-to-use epoxy and fiberglass kit designed to stop leaks in plastic tanks and metal radiators without removing the part.

If a coolant, washer fluid, or small storage tank is leaking, this repair kit provides the materials and instructions needed to seal holes and cracks quickly. The kit combines a two-part epoxy putty with fiberglass cloth, sandpaper, and an applicator so you can restore structural integrity and stop seepage on-site. It’s formulated to bond to plastic, metal, composites, and PVC, giving a durable repair where replacement would be costly or time-consuming.

How does this kit stop radiator and plastic tank leaks?

The kit uses a quick-curing epoxy putty reinforced with fiberglass cloth to form a rigid, waterproof patch. When mixed and applied, the putty adheres to the substrate and the fiberglass adds tensile strength for pressurized systems.

• Two-part epoxy putty creates a strong adhesive bond.
• Fiberglass cloth reinforces repaired area for durability.
• Designed to resist coolant and common fluids.
• Works on both plastic tanks and metal radiator surfaces.

What size damage can this repair kit handle?

This kit is suited for typical shop and roadside repairs: it fills holes up to about 3/8" diameter and repairs cracks up to 4" long when applied correctly. Larger or structurally critical failures may require replacement or professional welding.

• Holes: up to 3/8" diameter.
• Cracks: up to 4" length when reinforced with the included fiberglass.
• Surface prep required for best adhesion—cleaning and sanding included in kit.
• Can be applied without removing the tank in many cases.

How easy is it to use for a DIY repair?

The product is made for straightforward on-vehicle repairs and includes a simple step-by-step process. Mix the epoxy putty, apply the fiberglass cloth over the damaged area, smooth with the applicator, and allow the patch to cure according to instructions.

• No need to remove many tanks or radiators—in-place repairs possible.
• Includes sandpaper and an applicator for prep and finishing.
• Clear instructions make it accessible to mechanics and DIYers alike.
• Fast setup and curing times let you return the vehicle to service sooner.

How long will a repair last and what conditions affect performance?

A properly applied repair can hold under normal operating conditions for the life of the patched component, but longevity depends on surface prep, correct application, and the severity of damage. Avoid using the patch on parts subjected to extreme movement or temperatures beyond the product’s specifications.

• Best longevity achieved with thorough cleaning and sanding first.
• Designed for typical automotive coolant temperatures and pressures.
• Not recommended for permanently replacing severely cracked or collapsed tanks.
• Check and monitor the repair after initial heat cycles and driving.

Who is this for: This J-B Weld 2120 kit is aimed at auto mechanics, weekend DIYers, and fleet technicians who need a fast, cost-effective way to stop leaks in radiators and plastic tanks without immediate replacement. It’s especially useful for quick repairs on cars, trucks, and small equipment where downtime or part availability is an issue. For permanently failed cores, heavy structural damage, or high-stress components, consult a professional or consider replacement.