Replacing Freeze Plugs

Freeze plugs, or core plugs, are used to create passageways or cavities for coolant inside the engine of a car or truck. These plugs often develop leaks, allowing coolant to corrode surfaces in the vehicle's cooling system. To repair these leaks, leaking plugs must often be replaced. Some must be replaced by an experienced auto mechanic, but if you can replace your plugs in your vehicle yourself, you will undoubtedly reduce your replacement costs.

Things you'll need:

  • Drain pan
  • Hammer
  • Punch
  • Pliers
  • Socket wrenches
  • 6" Socket extension
  • Degreaser
  • Clean rags

Step 1 – Drain Engine Coolant

Before disconnecting the cooling system from the car's engine, drain all coolant into a drain pan. This will not only keep the coolant from spreading on the floor of your work space, but if you can re-use the coolant it will save you from having to buy more.

Step 2 – Remove Your Vehicle's Engine

You'll find it much easier to replace your freeze plugs if you pull your engine from your vehicle's engine compartment, before you begin attempting to remove and replace these plugs. If you are unable to remove the engine, remove engine parts that will interfere with your accessing the freezer plugs. Engine components you may need to remove might include your alternator, both the intake and exhaust manifolds, air filter and starter.

Step 3 – Loosen the Freeze Plugs

To loosen the freeze plug so you can remove it, position the point of your punch against the freeze plug edge, where it comes in contact with the engine block. Use a hammer to drive the punch against the edge of the plug, until the plug begins to rotate in the hole in which it is installed. Be careful to avoid damaging the car's engine block.

Step 4 – Removie the Freeze Plug

Once the plug is loose and will rotate freely, use a pair of pliers to pull it from the hole it is in. You may need to tap it with the hammer and punch, but do it gently, and be careful to avoid driving the plug into the coolant passage of the engine block.

Step 5 – Replacing the Plug

Part of the plug replacement procedure requires you to clean the hole from which you've removed the plug. Use a clean rag with a small amount of degreaser added to it, and remove any oil, dirt, or grease from the plug hole. Coat the new freeze plug edges with a surface treatment that helps seal and adhere the plug in the plug opening. Place the plug into the hole as far as you can. Then, find a socket large enough in diameter to cover the plug, place this socket against the top surface of the plug. Now, tap the socket with a hammer until the plug is driven all the way into its hole.

Step 6 – Replace Engine Components

When your plug is in place, reattach the components you removed earlier. With these components attached, close your radiator drain plug and refill the cooling system with water. Start your car engine and allow it to warm up, then check for leaks. If there are none, drain the water and fill the cooling system with coolant.