How to Fix a Leaky Car Radiator

Written by robert russell
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How to Fix a Leaky Car Radiator
Protect the radiator. (the future is here image by John Fatuzzo from

A number of factors can cause radiator leaks. It is not uncommon for cars to develop leaks as they age. Radiators can corrode and rust. Hoses can easily spring leaks. Radiators and radiator hoses become dry and cracked. Even though a leak may appear to be a minor problem, if left unintended it will lead to major damage to your vehicle.

Skill level:
Moderately Easy

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Things you need

  • Screwdriver
  • Drain pan
  • Radiator hoses, as needed
  • Set of wrenches
  • Cold weld epoxy

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  1. 1

    Inspect the radiator on a regular basis and be aware of the common signs of radiator leaks. The most common sign of a leak is a low coolant level. Develop the habit of visually inspecting the radiator from time to time. Another sign of a leak is a neon-green puddle under the car. The most common sources of radiator leaks are old hoses. Check the condition of the hoses. Signs of bad hose are cracks, dryness and bulges.

  2. 2

    Locate the leak. Use a garden hose to wash down the radiator and hoses. Turn the engine on and examine the radiator and hoses for leaks. A pin-sized hole in the hose can cause a leak. If the hose is indeed the problem, then this is an easy fix: swap out the hose with a new one. Simply unclamp the hose using a screwdriver and allow any coolant that comes out to spill into a drain pan. Tighten down a new hose in its place.

  3. 3

    Drain the radiator fluid. If the hose is not the problem and the leak is in the radiator itself, you can patch the radiator with cold weld epoxy. The plug for the coolant drain is on the bottom of the radiator on the passenger's side. Unfasten the plug with socket wrenches and allow the fluid to drain out in a drain pan.

  4. 4

    Clean the area around the leak, then apply epoxy to the area. To form a stronger seal, move the overflow line over to the vacuum port. Remove the distributor cap and start the engine a few times. This produces vacuum that will pull the epoxy into the leak and make a stronger seal.

  5. 5

    Let the epoxy cure for seven to eight hours. Refill the radiator. Check the coolant level later several hours later to make sure you have stopped the leak.

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