How to Remove Freeze Plugs/Core Plugs at Home

how to remove freeze plugs

A closer look at a combustion engine reveals core drillings. The cores act as coolant channels.

What is used to fill these sand casting cores are core or freeze plugs. The freeze plugs are often made of metal (sometimes plastic) and are inserted into the core bores by friction fitting.

Over time, the core plugs will leak due to corrosion from the cooling water system. They must then be removed without damaging the engine block. It is essential to find the correct technique for removing the freeze plugs.

1. Using a screwdriver and hammer

This technique will not work with the extremely corroded freeze plugs. First look for a hammer, channel lock pliers and a screwdriver with a flat tip. Insert the flat end of the screwdriver into the freezer plug and tap it with a hammer until the “eyelids” are raised and protrude.

Be careful not to push the freezing plug into the engine, otherwise, you will have some problems. Hit the side of the freeze plug, then use your lock pliers to remove the freezing plug.

Video of how to do it:

2. Freeze plug remover

freeze plug remover

The simplest way to remove the freezer plugs is to use a plug remover. With this device you can drill a hole in the middle of the freezing plug. Then you can remove it.

There are some other special devices that do not require you to drill a hole in the freezer plug, but these are often more expensive.

One tool kit that we have found really useful is this one from Amazon.

3. Block liquid seal

If the freezer plugs have a very small hole, it is not necessary to replace them every time. You can use a liquid block seal to seal the hole. However, this is a temporary solution as you may clog something else in the cooling system and eventually be forced to replace all the freezer plugs.

Expanding Replacement Freeze Plug

There are some freeze plugs that may necessitate the removal of the engine block or that are blocked by the gearbox. Expanding replacement freeze plugs contain a special material that expands when the plug is tightened. The best ones are those made of copper. This is best for hard to reach areas around the engine block.

What causes freeze plugs to leak?

Modern combustion engines are equipped with a cooling water system. The combustion ratio of an engine determines how efficient an engine is. However, a high compression ratio is associated with high engine temperatures.

The cooling water system helps to cool the engine and prevent damage to the piston rings and valves. Other components of this cooling system include the radiator, the connection pumps, the transmission cooler and the heater core.

At moments when this cooling system is exposed to very low temperatures, the water running in the cooling system freezes. Frozen water expands, causing unnecessary tension on the connecting pipes and the freezing plugs. You can find an anti-freeze solution to lower the temperature at which the water in the cooling system freezes.

Freeze plugs are designed to pop out when water freezes in the cooling system of a car. However, this happens quite seldom, and it can lead to a damaged engine block.

Purpose of the freeze plugs

Before any freeze plug removal procedure, it is important to understand why freeze plugs are present at all. The engine block is made of a sand casting. An engine mould is made and pressed onto a special type of sand. This creates an impression of the engine block, which is then moulded together with molten iron. This process makes engine blocks very strong and durable.

You will notice some cylinders on the engine block. The freeze plugs are used to close these holes.

The challenge in using freeze plugs is that they are made of very thin metal: galvanized steel. Over time, the freeze plugs are susceptible to rust. If you have an antifreeze solution in the engine block, you should not have problems with expanding freeze plugs.

However, many people are not aware that they need to use antifreeze to protect their freeze plugs.

Instead of using antifreeze, some people use brass freeze plugs. These are more expensive but have the added advantage of being rust-proof.

How do you know that your freeze plugs need replacement?

The first sign of a defective freeze plug is when coolant leaks from your vehicle. A leak in a freeze plug leads to a slow cooling system. Most freeze plugs are found on the side of the engine block, though one or two freeze plugs may perhaps be hidden between the transmission and engine block.

For the latter, you may need to have a mechanic nearby, as you will need to disassemble the transmission to reach them.

You will know that you have leaking freeze plugs if you notice that drops of water are leaking from the side of the engine block.

Engine Block Heaters

engine block heater

If you live in areas where the temperatures go below zero, it is advisable to have engine block heaters. The heater is used instead of the freeze plugs, which have the same diameter, with the main difference that they are equipped with a 110 volt cable attached to the end of the plugs.

When temperatures are extremely low, the freeze plugs heat up and prevent the engine block from freezing water. However, you must still use an anti-freeze solution, as the radiator still has cold water.

Final thoughts

Freeze plugs are marked as small depressions on the engine block. They are essential to prevent destruction of the engine block if the water inside the engine block freezes and expands. The freeze plugs “pop off” when this happens.

If you have antifreeze or engine block heaters, you do not need to worry about leaking freeze plugs. Freeze plugs are susceptible to rust, and this can lead to leaks. It is not easy to remove freeze plugs, as some plugs are located deep in the engine block between the transmission.

These may require you to disassemble the engine for replacement. The most common method for removing the freezing plugs is to use a flat screwdriver, scissors or pliers, and a hammer. Tap the freeze plugs in the middle until they pop out of the motor block.

Use the pliers to remove them. There is also a tool for removing freeze plugs; with this tool you can drill a hole in the middle of the plug and then pull it out.

Written by:

Magnus is the owner and main author of MechanicBase. He has been working as a mechanic for over 10 years, and the majority of them specialized in advanced diagnostics and troubleshooting. He has also been a motorsport (drifting) driver for over 5 years.