Tip & How-To about Ford Explorer

What is a freez plug??

A freeze or expansion plug is a small, metal, circular plug that lives in various places on an engine block. These plugs have a valuable function and an equally interesting origin. An engine block starts life as molten metal. In order to form an engine block, this metal is poured into a mold. When the metal cools off from a liquid to a solid, the engine block is born. As the mold is no longer needed, it is knocked away from the engine block. As most modern engines are liquid cooled, part of this mold also forms the cooling passages inside the engine and must be knocked away as well. The cooling jacket mold material is removed through the holes now filled by the freeze plugs.

Keep Your Cool
Along with filling holes, the freeze plugs have another function. Water expands when frozen. Metal on the other hand does not like to expand very much. If for some reason the liquid coolant inside the
engine block freezes and expands, the freeze plug is designed to pop out of the engine block to allow coolant to expand out of the hole. The inexpensive freeze plug can save thousands of dollars in cracked engine blocks. While all this is fine and good, freeze plugs will sometimes leak and fail for reasons that have nothing to do with cold weather. Neglected engine coolant becomes corrosive and can eat away at freeze plugs from the inside out and cause a leak. For these two reasons, maintaining engine coolant is important—on the one hand to prevent corrosion from forming, and on the other to maintain the correct level of anti-freezing properties during sub-freezing cold spells.
Holey Moley
While replacing a freeze plug in itself is fairly simple, getting to it may be another story. In fact, this story can be a long one. As bad luck will likely have it, the leaky freeze plug will never be the one that is easier to see than the sun at noon on a summer day. The leaking freeze plug will be the one up against the back of the firewall or underneath nearly every other part connected to the
engine. The additional unfortunate reality is that if one freeze plug has gone rusty with holes then the others are likely not far behind. The best time to replace freeze plugs is when the engine block is out of the car and up on a stand. If this is not an option then digging in and replacing that one leaking freeze plug may be the only answer.

Posted by on

Cars & Trucks Logo

Related Topics:

Related Questions:

1 Answer

replace freeze plug


If you look on the side of an engine block you will see a line of circular depressions about an inch and a half in diameter and about a quarter of an inch deep. These are actually holes in the side of the engine block which are plugged with a dish shaped metal plug called a "freeze plug" or "expansion plug".

WHAT FREEZE PLUGS DO

As with many things on a car, there is an "official reason" and a "REAL" reason for freeze plugs. The official reason (and the source of the name) is this: If you run just water with no antifreeze in your car the water can freeze. When water freezes, it expands. If water freezes inside your engine block, it can expand and crack the block, destroying the motor. Freeze plugs (or expansion plugs) will "pop out" and supposedly prevent this. In reality this doesn't work all the time: I've seen MANY blocks destroyed by cracking without the freeze plugs popping out, or if they do pop out the block cracks anyway.

THE REAL PURPOSE OF FREEZE PLUGS

Engines are "sand cast". A special type of sand is poured into a pair of boxes. A "die" is pressed into the sand, making an impression of the engine block to be cast. The sections of the mold are then put together and molten iron is poured in, forming the engine. This is why engines have a rough texture on most areas: this is the texture of the sand used to cast them.

There have to be "cylinders" made of sand in the middle of this mold to create the cylinders of the engine block. These chunks of sand can't just "float" inside the mold: SOMETHING has to hold them in place. There are little columns of sand that connect the cylinder mold to the outer mold half. The mold for the cylinder "sits" on top of these. After the block is cast, these holes are machined smooth and a "freeze plug" is put in to plug the hole.

THE PROBLEM WITH FREEZE PLUGS

The problem with freeze plugs is that they are made of very thin metal, AND THEY RUST!!! From the factory they are made of galvanized steel, and if you always run a 50/50 mix of antifreeze you should never have a problem. Unfortunately many people don't do this, and the freeze plugs rust through, creating a coolant leak.

When I replace freeze plugs or rebuild an engine I always use brass plugs: they only cost a tiny bit more and will not rust through. The manufacturers, of course, will save a penny anywhere they can: pennies add up to millions of dollars!

SIGNS OF BAD FREEZE PLUGS

If you have a bad freeze plug your vehicle will leak coolant. Freeze plugs are in different places on different cars, but normally they will be down the side of the block (at least 3 of them) and in the back of the block, between the engine and the transmission. Some are fairly easy to get to, others require removing various parts off the engine, some even require removing the transmission or engine to replace! Some cylinder heads also have smaller plugs in them, often under the intake or exhaust manifold.

So if you have water leaking down the side of your engine, or water leaking from the hole in the bell housing between the engine and transmission, you probably have a bad freeze plug.

FREEZE PLUG REPAIR

If the leak is slow and small, a stop leak or block seal compound might work. I have had good luck with K&W Liquid Block Seal: it's good stuff! Of course, as with any "rig" of this sort, it might not work, might not last for long, and could clog up something else in your cooling system. The right way to fix it is to replace the freeze plug.

FREEZE PLUG REPLACEMENT

To remove a freeze plug, first hammer it into the block with a big screwdriver or a large punch. It won't go far into a modern engine: there isn't much room behind the plug. When it "pops through" you can easily pry it back out of the hole sideways with a pair of pliers or a screwdriver. Be careful not to scratch the surface of the hole where the plug sits, or it could leak around the circumference of the new plug.
After the plug is removed, clean the hole in the block with sandpaper to remove the corrosion and old sealant. Once again, if you don't do this the new one might leak.

Normal freeze plugs are hammered in with some sealant around them. I use aviation grade Permatex sealer. If you can't get to them to do this, you have to take off whatever parts are in the way to access the plug. If access is limited, they make replacement freeze plugs made of copper and also ones made of rubber with a nut on them which expands the plug against the block when tightened. I have had bad luck with the rubber type: they blow back out quite often. I have had good results with the copper type (made by Dorman).
I have not had good results with either type on Ford products: Ford for some reason makes their freeze plugs in "odd" dimensions, like 1 and 51/64 of an inch. You can get the copper type plug in 1/8 th increments, but it won't expand enough to fit the Ford size. The rubber type will SEEM to expand enough, but it will stay in for a week or so then blow out, dumping all your coolant out in a matter of seconds!!!

So on all Fords I just do whatever it takes to pound a regular style brass plug into the block.

Here are some pictures of a Ford F-150 truck I just did. The hard part is taking the exhaust and intake manifolds off: after that the job is easy.

Apr 04, 2014 | 1995 Chevrolet Lumina

1 Answer

weep hole on back of engine, what is it for?


there should be a metal plug inset in the hole, it is called a freeze plug. It's purpose is for if your water or coolant freezes the plug is designed to pop out of the block so that the motor block won't crack from the expansion when liquid freezes. It is a lot easier and cheaper to replace a freeze plug than to replace the whole motor block.

Jan 02, 2014 | 2000 Chrysler LHS

1 Answer

The block heater cord to 2004 jetta came unplugged from the car and I'm not sure where to look to plug it back in Can someone give me a general idea where it might go?


Block heaters are installed on the engine block in one of the "freeze plug" openings. The freeze plug is punched out and the block heater is installed in its place. The freeze plugs, about 3 on each side of the engine, are midway up the block- a round, slightly recessed metal plug about 2 inches in diameter that is driven into these holes made during the engine casting process. The freeze plugs will be found below where the exhaust manifold attaches-so if you are looking on the side of the engine with the exhaust manifold-look behind and just below the exhaust manifold. The other side of engine will have the same number of freeze plugs at the same level on the engine block.
Your block heater is probably on the front facing side of the engine (towards the radiator). It is probably shinier than tom the he regular freeze plugs, will have a small screw in the center for tightening when installed, and will have 2 or 3 metal prongs that your heater cord attaches to. Simply plug it back into the heater. Just remember: about halfway up on the engine block, from the oil pan rail at bottom to the top of block where the cylinder head mates.

Dec 13, 2013 | Cars & Trucks

3 Answers

I have a 1998 Ford Expedition. I have been told that I have a bad coolant leak coming from rear freeze plug and that I should replace the engine. My question is, do the engine need too be replaced or do I just replace the freeze plug.


If you look on the side of an engine block you will see a line of circular depressions about an inch and a half in diameter and about a quarter of an inch deep. These are actually holes in the side of the engine block which are plugged with a dish shaped metal plug called a "freeze plug" or "expansion plug". WHAT FREEZE PLUGS DO As with many things on a car, there is an "official reason" and a "REAL" reason for freeze plugs. The official reason (and the source of the name) is this: If you run just water with no antifreeze in your car's cooling system the water can freeze. When water freezes, it expands. If water freezes inside your engine block, it can expand and crack the block, destroying the motor. Freeze plugs (or expansion plugs) will "pop out" and supposedly prevent this. In reality this doesn't work all the time: I've seen MANY blocks destroyed by cracking without the freeze plugs popping out, or if they do pop out the block cracks anyway. THE REAL PURPOSE OF FREEZE PLUGS OR EXPANSION PLUGS Engines are "sand cast". A special type of sand is poured into a pair of boxes. A "die" is pressed into the sand, making an impression of the engine block to be cast. The sections of the mold are then put together and molten iron is poured in, forming the engine. This is why engines have a rough texture on most areas: this is the texture of the sand used to cast them.There have to be "cylinders" made of sand in the middle of this mold to create the cylinders of the engine block. These chunks of sand can't just "float" inside the mold: SOMETHING has to hold them in place. There are little columns of sand that connect the cylinder mold to the outer mold half. The mold for the cylinder "sits" on top of these. After the block is cast, these holes are machined smooth and a "freeze plug" or "expansion plug" is put in to plug the hole.
THE PROBLEM WITH FREEZE PLUGS OR EXPANSION PLUGS The problem with freeze plugs or expansion plugs is that they are made of very thin metal, AND THEY RUST!!! From the factory they are made of galvanized steel, and if you always run a 50/50 mix of antifreeze in your cooling system you should never have a problem. Unfortunately many people don't do this, and the freeze plugs rust through, creating a cooling system leak.When I replace freeze plugs or rebuild an engine I always use brass plugs: they only cost a tiny bit more and will not rust through. The manufacturers don't use brass plugs of course: they cost a few cents more, and they will save a penny anywhere they can: pennies add up to millions of dollars!
SIGNS OF BAD FREEZE PLUGS If you have a bad freeze plug your vehicle will leak coolant. If you have a slow cooling system leak that comes and goes, you may have a pinhole freeze plug leak. l Freeze plugs are in different places on different cars, but normally they will be down the side of the block (at least 3 of them) and in the back of the block, between the engine and the transmission. Some are fairly easy to get to, others require removing various parts off the engine, some even require removing the transmission or engine to replace! Some cylinder heads also have smaller plugs in them, often under the intake or exhaust manifold.So if you have water leaking down the side of your engine, or water leaking from the hole in the bell housing between the engine and transmission, you probably have a bad freeze plug. Sometimes the hole in the freeze plug is very small, and can periodically stop when a piece of crud from the cooling system jams in the hole.
FREEZE PLUG REPAIR If the leak is slow and small, a stop leak or block seal compound might work. I have had good luck with K&W Liquid Block Seal: it's good stuff! Of course, as with any "rig" of this sort, it might not work, might not last for long, and could clog up something else in your cooling system. The right way to fix it is to replace the freeze plug. FREEZE PLUG REPLACEMENT To remove a freeze plug, first hammer it into the block with a big screwdriver or a large punch. It won't go far into a modern engine: there isn't much room behind the plug. When it "pops through" you can easily pry it back out of the hole sideways with a pair of pliers or a screwdriver. Be careful not to scratch the surface of the hole where the plug sits, or it could leak around the circumference of the new plug.
After the plug is removed, clean the hole in the block with sandpaper to remove the corrosion and old sealant. Once again, if you don't do this the new one might leak.Normal freeze plugs are hammered in with some sealant around them. I use aviation grade Permatex sealer.
A special tool is made to install freeze plugs: the tool is available at a good auto parts store. In a pinch you can use a large socket that just barely fits inside the rim of the plug, however this can damage the new plug if you aren't careful.
If you can't get to the freeze plug to hammer it in, you have to take off whatever parts are in the way to access the plug. Sometimes it's easier to remove the engine from the car. Another option when access is limited is an expanding replacement freeze plug. These replacement plugs are made of either copper or rubber. A nut on them expands the plug against the block when tightened. These plugs can be installed in areas too tight to hammer in a regular freeze plug. I have had bad luck with the rubber type: they blow back out quite often. I have had good results with the copper type (made by Dorman).
I have not had good results with either type on Ford products: Ford for some reason makes their freeze plugs in "odd" dimensions, like 1 and 51/64 of an inch. You can get the copper type plug in 1/8 th increments, but it won't expand enough to fit the Ford size. The rubber type will SEEM to expand enough, but it will stay in for a week or so then blow out, dumping all your coolant out in a matter of seconds!!!
So on all Fords I just do whatever it takes to pound a regular style brass plug into the block.

Here are some pictures of a Ford F-150 truck freeze plug job I did.

The hard part is taking the exhaust and intake manifolds off: after that the job is easy. CAUTION! I have one issue with this freeze plug video: He uses no sealant on the new freeze plugs, and he's not using brass freeze plugs.
I always use aviation grade permatex sealant on freeze plugs. It's available at any good auto parts store.Don't use RTV silicone: I've seen freeze plugs "pop out" with silicon seal.
Freeze plugs will work when put in "dry", but they might "weep" a small amount of coolant.
ef89772a-3f1b-412b-bc7a-627f024dd76b.jpg c9d84666-d779-46c8-a9ee-4ee71a71ad14.jpg 0626e0f3-8efc-4409-ab0c-cc4923e4ee96.jpg b89a2ab0-aba7-4b01-a2ee-d5f4ad94c546.jpg 41560920-4b57-4ef8-af06-69d69c2463bd.jpg

Apr 03, 2013 | Cars & Trucks

1 Answer

Where are the freeze plugs located on a 1997 chevy s-10 truck?


A freeze or expansion plug is a small, metal, circular plug that lives in various places on an engine block. These plugs have a valuable function and an equally interesting origin. An engine block starts life as molten metal. In order to form an engine block, this metal is poured into a mold. When the metal cools off from a liquid to a solid, the engine block is born. As the mold is no longer needed, it is knocked away from the engine block. As most modern engines are liquid cooled, part of this mold also forms the cooling passages inside the engine and must be knocked away as well. The cooling jacket mold material is removed through the holes now filled by the freeze plugs.

Keep Your Cool
Along with filling holes, the freeze plugs have another function. Water expands when frozen. Metal on the other hand does not like to expand very much. If for some reason the liquid coolant inside the
engine block freezes and expands, the freeze plug is designed to pop out of the engine block to allow coolant to expand out of the hole. The inexpensive freeze plug can save thousands of dollars in cracked engine blocks. While all this is fine and good, freeze plugs will sometimes leak and fail for reasons that have nothing to do with cold weather. Neglected engine coolant becomes corrosive and can eat away at freeze plugs from the inside out and cause a leak. For these two reasons, maintaining engine coolant is important—on the one hand to prevent corrosion from forming, and on the other to maintain the correct level of anti-freezing properties during sub-freezing cold spells.
Holey Moley
While replacing a freeze plug in itself is fairly simple, getting to it may be another story. In fact, this story can be a long one. As bad luck will likely have it, the leaky freeze plug will never be the one that is easier to see than the sun at noon on a summer day. The leaking freeze plug will be the one up against the back of the firewall or underneath nearly every other part connected to the
engine. The additional unfortunate reality is that if one freeze plug has gone rusty with holes then the others are likely not far behind. The best time to replace freeze plugs is when the engine block is out of the car and up on a stand. If this is not an option then digging in and replacing that one leaking freeze plug may be the only answer.

Mar 13, 2010 | 1997 Chevrolet S-10 Pickup

Not finding what you are looking for?

700 people viewed this tip

Ask a Question

Usually answered in minutes!

Top Ford Experts

yadayada
yadayada

Level 3 Expert

76846 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22246 Answers

fordexpert

Level 3 Expert

5546 Answers

Are you a Ford Expert? Answer questions, earn points and help others

Answer questions

Loading...