How to Change a Freeze Plug by the Motor Mount

by Chris Stevenson
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Auto Engine image by Andrew Breeden from

Freeze plugs exist because of the manufacturer's casting holes left over from engine blocks and cylinder heads. They appear as circular holes in the outside of the head or block, and have metal pressure-fitted plugs that keep the water inside the engine. When freeze plugs rust or blow out, they leak and must be replaced. Some freeze plugs have difficult access locations, like those that sit next to motor mounts. Fortunately, an average auto repair person can replace his hard-to-reach freeze plug by using a few simple tools and extraction tips.

Step 1

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.

Step 2

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.

Step 3

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.

Step 4

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.

Step 5

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.

Step 6

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.

Step 7

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.

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