How to Patch a Plastic Radiator End Tank

Written by mary lougee
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How to Patch a Plastic Radiator End Tank
Radiator end tanks supply additional antifreeze to the radiator for engine cooling. (American v8 engine image by kenmo from

A plastic radiator end tank, or expansion tank, holds excess antifreeze. When an engine is at operating temperature, the thermostat opens and allows antifreeze from the radiator into the engine to cool it. The radiator suctions excess antifreeze from the end tank to keep the radiator full. After turning an engine off, the excess antifreeze flows from the radiator into the expansion tank. If an expansion tank is leaking, there will be a noticeable antifreeze odour when a vehicle is turned off and the level will not stay at the fill line.

Skill level:

Things you need

  • Screwdriver
  • Adjustable wrench
  • Isopropyl alcohol
  • Shop towel
  • Vinyl patch
  • Epoxy glue
  • Putty knife

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  1. 1

    Turn the vehicle off and allow the engine to cool completely.

  2. 2

    Place a screwdriver in the hose clamp on the plastic tank. Turn the worm screw counterclockwise to loosen the band. Pull the radiator overflow hose off the tank. The radiator overflow hose is the small hose at the radiator top that leads to the plastic expansion tank.

  3. 3

    Remove the mounting bolts on the plastic tank that hold it into the firewall with an adjustable wrench. Turn each bolt counterclockwise to loosen it and pull it straight out. Remove the plastic tank. Open the cap on the tank and pour the antifreeze out. Let the tank dry completely in the repair area.

  4. 4

    Pour isopropyl alcohol on a shop towel. Clean the area with a hole or crack with the alcohol to extend 3 inches past the defect on all sides.

  5. 5

    Squirt epoxy glue on the repair area of the tank. Press a vinyl patch onto the glue and smooth out all air bubbles. Place a putty knife in the centre of the patch and press outward on all sides to remove the air bubbles. Let the patch dry according to the package directions on the epoxy.

  6. 6

    Replace the tank in the vehicle and attach each bolt. Turn each bolt clockwise with an adjustable wrench to tighten it. Press the hose onto the plastic tank. Place a screwdriver in the hose band and turn it clockwise to tighten the radiator overflow hose.

  7. 7

    Fill the plastic tank with a solution of 50 per cent antifreeze and 50 per cent water to the "cold" fill line. Press the filler lid down to close it.

Tips and warnings

  • Plastic repair kits, including the vinyl patch and the epoxy glue, are available at automotive supply stores

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