How to Replace Freeze Plugs in Engines

by Emily Retherford
itstillruns article image
old engine image by John Sfondilias from

Freeze plugs are used to keep the antifreeze and water from freezing inside your engine, which could cause your engine head to crack. If the temperature drops and you haven't driven your vehicle for a while, the freeze plugs automatically "pop." This saves your engine, but the freeze plugs need to be replaced before you can drive your car again.

Step 1

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.

Step 2

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.

Step 3

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.

Step 4

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.

Step 5

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.

Step 6

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.

Step 7

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.

More Articles

article divider