How to fix a fuel tank or radiator leak: a temporary repair with epoxy putty

You can fix a fuel tank leak or a leaking radiator yourself with epoxy putty: a two-component compound that you knead with your fingers and apply to the crack or hole on the outside of the emptied, cooled part. Metal tanks and radiators, including aluminium ones, are repaired with NANOPROTECH Metal epoxy putty. This is a temporary repair until the part is replaced: fuel and coolant are refilled after 24 hours, and an exhaust silencer is not repaired with epoxy putty.

What you need

Metal epoxy putty, 55 g

Two-component cold weld, 55 g

Multipurpose epoxy putty, 55 g

Two-component cold weld, 55 g

Which epoxy putty to choose

• Steel fuel tank. Metal epoxy putty is designed for steel, including stainless steel, aluminium and brass; fuel tanks are on its list of uses, and the cured putty resists chemical reagents.
• Cooling radiator. A metal radiator, including an aluminium one, is repaired with the metal putty, and plastic radiator tanks with Multipurpose epoxy putty. On thin tubes and the core the repair does not last long: it is a stopgap until a garage repair.
• Plastic fuel tank. These tanks are usually made of polyethylene, which epoxy putty hardly sticks to. A plastic tank is repaired at a garage or replaced.
• Exhaust silencer. The silencer and exhaust system are not repaired with epoxy putty: with the engine running they get hotter than +150 °C, the limit of the putty's heat resistance. They are welded or replaced.

How to fix a fuel tank leak with epoxy putty — step by step

1. Drain the fuel or coolant. Remove or empty the tank and ventilate it well, outdoors or in a ventilated room. Drain the coolant from the radiator, let it cool and rinse the leak area with water.
2. Prepare the repair area. Clean off dirt and rust and rough the surface up with coarse sandpaper by hand, not with a power tool, to avoid sparks. Then degrease and dry it.
3. Cut off and knead the putty. Cut off at least 1/3 of the stick and, wearing protective gloves, knead both components with your fingers until the colour is uniform. You can wet your fingers with water.
4. Cover the crack or hole. Apply the putty to the repair area from the outside and press it on firmly. If oil residue could not be removed, keep smoothing the putty until it grips: on an oily surface the bond strength is 20% lower.
5. Shape the seam. Smooth the putty with a flat object moistened with water.
6. Wait for full curing. The putty sets in 45 minutes, and after 2.5 hours the seam can be sanded and painted. Refill fuel and coolant after 24 hours, then check for drips and replace the part as soon as you can.

For details on mixing and storing the stick, see how to use epoxy putty.

Why it may not work

• The wrong repair method was chosen. Epoxy putty will not hold on a polyethylene tank, and a silencer gets hotter than +150 °C.
• Fuel, oil or antifreeze was left on the surface. Rinse, degrease and dry the repair area: on an oily surface the bond strength drops by 20%.
• The putty was not fully mixed. Knead it until the colour is completely uniform.
• The part was refilled too soon. Fuel and coolant are refilled 24 hours after application, once the putty has fully cured.

Safety precautions

• Petrol vapour in an empty tank is explosive: drain the fuel, ventilate the tank, do not smoke and do not work near open flames.
• Clean the tank by hand, not with a power tool, and do not speed up curing with heat.
• Wear protective gloves and keep the stick components out of your eyes. If they get in, rinse with water and seek medical advice.
• Epoxy putty is a temporary repair: replace the tank or radiator, or take the car to a garage, as soon as you can.
• Keep the sticks out of the reach of children.

Frequently asked questions