How to Change the Freeze Plug on Vehicles

by Contributing Writer

Engine freeze plugs exist on the typical automobile engine as a result of casting holes in the block or head. The holes must be incorporated into the block and head to allow escaping air during the hot-melt pour and casting process. The holes have circular shapes in varying diameter sizes, and receive steel or brass plugs to enclose the casting holes. Metal freeze plugs have pressed installation fittings, designed to hold back jacketed engine water. When freeze plugs rust or deform, they leak and drain the block or head of coolant. Replacing freeze plugs requires more labor cost than part's cost, but some procedures and tools can simplify the process.

Under The Hood:

 How to Change the Freeze Plug on a Buick 3.8 Engine

Position a punch at the outside edge of the freeze plug. Tap it with a hammer so that it rotates on its middle. When the edge of the plug clears the engine block, grip it with a pair of pliers and remove it from the engine block.

Wipe the inside of the hole with a small piece of emery cloth. Wipe forward with quick strokes to make sure nothing gets trapped inside the engine.

Coat the edges of the new freeze plug with a thin layer of shellac.

Set the freeze plug firmly into a seal driver. Push the seal driver against the hole in the engine block, then turn it counter-clockwise until the freeze plug is seated.

Items you will need

  • Punch

  • Hammer

  • Pliers

  • Emery paper

  • Shellac

  • Application brush

  • Seal driver

 How to Change a Freeze Plug by the Motor Mount

Place the shift selector in neutral or park, for the type of transmission you have. Raise the hood and disconnect the negative battery cable at the terminal with a socket. Raise the front of the vehicle with a floor jack and place to jack stands under the frame. Raise the rear of the vehicle and place two jack stands under the frame.

Place a drain pan underneath the lower radiator hose. Unscrew the clamp on the radiator hose and pull the hose free, with a twist. Let the coolant drain into the pan. Replace the hose on the neck fitting and tighten the clamp with a screwdriver.

Take a shop light underneath the vehicle and secure it next to the freeze plug location. If you cannot get a finger or screwdriver on the damaged freeze plug, place a breaker bar and socket on the (horizontal) motor mount through-bolt nut. Fit an end wrench onto the motor mount bolt head. Loosen the motor mount nut with a the breaker bar. Tap the bolt out with a drift punch and hammer.

Wheel the floor jack under the engine. Place a wood block edge-wise between the jack spoon and the lip of the oil pan, on the freeze plug side. Pump the jack up only a few inches, to gain access to the freeze plug. Take the drift punch and place it on the freeze plug. Strike the punch several times with a hammer to knock the metal plug out.

Clean the freeze plug hole with carburetor cleaner and a wire brush. Wipe the hole seat clean with a rag. Push a rubber, screw-in freeze plug in the hole and twist it in so that it seats flush. Use an end-wrench to tighten the freeze plug bolt until the plug expands. Tighten it firmly, but do not over-tighten it or you will crush the rubber plug.

Release the pressure on the floor jack. Remove the jack, shop light and wood block. Push the motor mount bolt back into its hole. Tap the bolt through the motor mount with the hammer and drift punch. Screw on the motor mount nut by hand. Hold the bolt head with an end-wrench, while you tighten the bolt head nut with a socket and breaker bar.

Refill the radiator with the amount of coolant you removed. Secure the radiator cap tight. Start the engine and let it warm up to operating temperature. Take the shop light underneath the vehicle and check for any seepage from the freeze plug. Raise the vehicle with the floor jack and remove the jack stands. Test driver the vehicle and recheck for any leaks.

Items you will need

  • Floor jack

  • Jack stands

  • Screw drivers

  • Drain pan

  • Shop light

  • Socket Set

  • End wrenches

  • Ratchet wrench

  • Breaker bar

  • Wood block

  • Drift punch

  • Hammer

  • Wire brush

  • Carburetor cleaner

  • Rags

  • Freeze plug (rubber insert, screw-on)

  • Coolant

 How to Change the Freeze Plug on a 4.3 L Vortec Engine

Place a large pan under the radiator and take out the drain plug with a wrench. Drain the coolant into the pan, then place the pan of coolant to one side. Replace the drain plug.

Hit the side of the old freeze plug with the drift and the hammer. The old plug will swivel in the hole. Take it out with the pliers.

Rub the emery cloth around the inside of the freeze plug hole.

Coat the bearing surface of the new freeze plug with sealant. If the manufacturer of the sealant recommends a waiting period while the sealant sets or cures, wait until that time has passed. Press the new freeze plug into the hole and seat it with gentle blows of the hammer.

Put the sealer head inside the new freeze plug. Drive it further inside the freeze plug hole with the hammer until it's 1/16 of an inch below the surface of the engine block.

Put the coolant back into the radiator and start the engine.

Test the new freeze plug for leaks.

Items you will need

  • Emery cloth

  • Socket or seal driver

  • Drift

  • Screwdrivers

  • Adjustable wrench

  • Jack

  • Jack stands

 How to Replace the Freeze Plugs on a Dodge Dakota

Get under the truck and drain the coolant by removing the drain plug with the adjustable wrench. Drain the coolant into a pan and put aside. Replace the drain plug.

Put the drift on the freeze plug toward the side and tap it with the hammer. The plug should turn inside the freeze plug hole.

Take the plug out with the pliers. Sometimes freeze plugs have corroded inside the freeze plug hole. If this happens, punch a hole in the center of the freeze plug with a small screwdriver and pry it out.

Rub the emery cloth around the inside of the freeze plug hole to clean it. Remove any residue or dirt.

Coat the sides of the new freeze plug with sealant. Gently insert the freeze plug into the freeze plug hole. Hit it around the edges with the hammer, using gentle pressure to seat the freeze plug completely into the freeze plug hole.

Fit the sealer head into the freeze plug. The sealer head is designed to fit closely and will push the freeze plug into the block until it is a sixteenth of an inch below the surface of the plug.

Replace the coolant and start the engine. Check for leaks.

Items you will need

  • Freeze plug kit

  • Emery cloth

  • Socket or seal driver

  • Sealant

  • Drift

  • Adjustable wrench

  • Pliers

  • Screwdriver

 How to Replace Freeze Plugs in a Mustang

Place the vehicle in park or neutral, depending upon your transmission type. Set the emergency brake firmly. Raise the hood and disconnect the negative battery cable with a socket and wrench. Use a floor jack to lift the vehicle front end and place two jack stands under the frame, extended at full height. Raise the rear of the vehicle and place two jack stands under the frame at full height. Place a drain pan under the radiator.

Use pliers to to loosen the radiator petcock valve and let the coolant drain into the pan. Remove the radiator cap to facilitate a faster drain. Take a shop light under the vehicle and locate the leaking freeze plug.

Refer to your owner's manual for all of your freeze plug locations, if you need to replace all of them. To remove a freeze plug out in the open on the side of the engine block, place a long-handled chisel on the lip of the plug and strike it with a hammer. Strike it until the plug twists and bevels outward. Remove the plug with a pair of pliers. For a freeze plug that sits behind a motor mount, remove the motor mount bolt and nut with a socket.

Place a floor jack under the oil pan, with a block of wood on the lifting spoon. Raise the engine for enough clearance to use the hammer and chisel, but not high enough to bind the exhaust system or twist the transmission. After removal of the plug, use a wire brush to thoroughly clean the casting hole. Wipe it clean with a rag.

Place a dab of silicone on the edge of a new freeze plug and squarely wedge it in the casting hole. Use a hammer and back of a large socket to tap the metal freeze plug into the casting hole until it seats. If you must use a rubber expansion plug, lubricate the edge of the plug with some silicone.

Place the freeze plug into the casting hole and tap it into its seat with a hammer. Use a socket to turn the expansion plug nut clockwise until the rubber plug pressure fits solidly in the hole. Replace all freeze plugs in this fashion, using either the metal-type plugs, or the rubber expansion-type for hard to reach areas. If you removed a motor mount bolt, lower the floor jack and align the motor mount hole. Insert the bolt and nut and tighten it with a socket.

Use pliers to close the radiator petcock valve. Refill the radiator with coolant to the proper level and seal the radiator cap. Use the floor jack to raise the vehicle and remove the front and rear jack stands. Reconnect the negative battery cable with a socket. Start the engine and let it warm up. Check for leaks at the new freeze plug location.

Items you will need

  • Mustang repair manual

  • Socket set

  • Ratchet wrench

  • Floor jack

  • Jack stands

  • Drain pan

  • Pliers

  • Shop light

  • Hammer

  • Chisel

  • Wood block

  • Wire brush

  • Rags

  • Freeze plugs

  • Rubber expansion plugs (if applicable)

  • Silicone (waterproof)

  • Coolant

 How to Replace Freeze Plugs in Engines

Drain the antifreeze from your car so it doesn't spill on the ground when you remove the freeze plug. Slide under the vehicle and place a drain bucket under the petcock. The petcock is a small valve with a handle located on the bottom of the radiator. Loosen the petcock to allow the radiator to drain. Sometimes the handle is too tight to turn by hand, if so use a pair of pliers to loosen it.

Remove the parts blocking your way to the freeze plugs. The parts vary depending on what kind of vehicle you have, but you may need to remove the alternator, intake manifold or the exhaust manifold.

Break the freeze plug free. Simply take the sharp punch and put it against the edge of the freeze plug. Then hit the punch with a hammer lightly. This may need to be repeated several times to break the freeze plug free. You want the freeze plug to spin in the hold it is in; make sure you don't scratch the engine while doing this.

Remove the freeze plug. Carefully grab the plug with the pliers so you don't push the plug into the block's coolant. If you have trouble pulling the freeze plug out, angle the plug to the side before pulling it out. That will lift one side a little to make it easier to grab onto.

Clean the hole that the freeze plug came out of. Using degreaser and some rags, thoroughly clean the hole where the new freeze plug will go. The new plug won't seal properly if there's leftover grease coating the hole.

Place the new freeze plug in the hole. Then place a socket wrench that is the same size as the plug over the freeze plug to protect it. Lightly tap the socket wrench with the hammer until the plug sits flush with the engine. Put loc-tite around the entire outer edge of the plug to seal it in place.

You will now need to put the parts back on that you had to remove to get to the freeze plugs. Once everything is back on, be sure to tighten up the petcock. Once the petcock is tight, add the antifreeze that you drained out of it.

Items you will need

  • Clean drain bucket

  • Pilers

  • Punch

  • Hammer

  • Degreaser

  • Clean rags

  • Large socket set

  • Loc-tite

 How to Replace Freeze Plugs in an OMC Cobra 4.3 Liter Engine

Place the boat in an area where the engine will thaw out and the coolant will unfreeze. This may require removing the boat from the water and placing it in a heated warehouse or garage. If the freeze plug blew out because of rust, you can skip this step.

Drain any coolant left in the radiator. If the freeze plug completely blew out and all of the fluid drained, you can skip this step. However, take time to clean up the spilled coolant, as it is toxic. Clean it up with old rags and then properly dispose of the rags and coolant per your local disposal laws.

Locate the defective freeze plug. Depending on the year of your engine, the plugs are 1 5/8-inch diameter or 1 ¾-inch in diameter. They are located in a row on the bottom edge of the block on either side. Each plug has a raised lip. Inspect the lips. If you see any of the lip separated from the block, remove the plug. If the plugs have rust on them, remove them and replace them. To remove them, pull on the raised lip with a pair of pliers. The plugs are relatively thin metal and will pull out rather easily.

Wipe the surface of the block clean and then clean out the hole that you removed the plugs from. You will have a moderate amount of sludge left in the engine block. Clean as much out as you can. Make sure the hole and the area around the hole is clean before reinstalling new plugs.

Place the plug into the hole and tape the plug in place with a rubber mallet. Make sure the head of the rubber mallet is larger than the diameter of the plug. This will prevent damaging the plug when installing it. Continue to pound the plug in place until the raised lip seats onto the engine block. Repeat this with each plug you replace.

Fill the radiator with 50/50 mix of radiator fluid and distilled water.

Items you will need

  • Rags

  • Pliers

  • Brass freeze plugs

  • Distilled water

  • Radiator fluid