Diagram 3800 engine

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.

check soft plugs in the back of the engine block (also called freeze plugs) which are there for the purpose of expansion in cases of freezing solid in order to prevent the engine block from cracking under the pressure of freezing. its not a costly repair if you can get to the plug to replace it yourself ? if not get it to a shop pronto because soon the temps outdoors will increase causing overheating of the engine to occur without proper coolant capacity. Good Luck and i hope this helps you.

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.

Yes, actually they are casting plugs that hold the supports for the inner sand core that allow casting a water channel in the block. Steel plugs are hammered into these holes to seal up the block, and in the old days when people used alcohol antifreeze that often boiled off and left pure water in the block, and it froze. The expansion of freezing water pushed thes steel plugs out if you were lucky and did not split the block.

There is one of these plugs on the back of the engine, especially if the engine is a cast iron block. You may be able to put in some antifreeze that has more antileak compound than normal antifreeze. Check with a parts supply store. Also see http://wiki.answers.com/Q/How_do_you_fix_an_antifreeze_leak

be aware that some sealants clog the radiator at times.

Yes take it out. You can tap it with a flat head screwdriver on an angle until its through. Then carefully pry it out. If you're not comfortable doing it this way drill a half inch hole in it to relieve the seal.
Pour a jug of pure antifreeze in where the thermostat is. (remove it first)
This may also keep your block from cracking.

If it has a block heater, simply plug it in and disregard all of the above.

you engine has about 10 freeze plugs,there were created to be pushed out by ice if your antifreeze wasn't strong enough and froze inside the engine,that way the ice didn't crack the block when it expanded.
what causes freeze plugs to leak is the erosion affects from the antifreeze we use today,when they tell you to change your antifreeze every couple of years,the freeze plugs take another shot of strong antifreeze again,they just rust up on the inside of the engine until they get a rust hole in them

From what you described I suspect you have a hole in a freeze plug. They tend to rust out over the years, especially if you’re running a high percentage water and a low percentage antifreeze for your coolant. Try to fill your radiator when the engine is cold. If you have a hole in a freeze plug you won't be able to keep the radiator full. The water will just keep running out the hole. If you can fill the radiator and don't see any leaks, it's probably not a freeze plug. It may be a sliced hose that will only leak when the engine is warm. If you do have a leak, try to look under the car and see where the water is coming from. Freeze plugs look like round shallow indentation in the engine block. They're usually about 1.5 inches in diameter. If you find a leaking freeze plug you can usually pop it out by driving a large screwdriver into the hole and then use the screw driver to pry the metal freeze plug out. Buy a new freeze plug of the same size at an auto parts store and tap it back into the circular opening. Do your best to clean the edges of the opening first. Put one end of a deep well socket that's slightly smaller than the freeze plug against the outer wall of the freeze plug and tap on the other end of the socket with a hammer to drive the plug into the opening in the engine block. This will help you to drive it in straight. If there's enough room to swing a hammer, freeze plugs usually aren't too difficult to replace. However, if there's no working room they can be very difficult to replace. If this is the case you may want to take it to a garage.

First, No your truck engine shouldn't need to come out if it is a frost plug. May be hard to get at but most times patience & the right tool will pop that bad one out for you if thats what it is. Do yourself a favor though, unless its the hole with a block heater in it, just by a rubber plug (similar to a thermos plug) designed to replace the metal frost plug. take your old plug with you for correct sizing. It's just a round plug with a nut in the center that you tighten once you've put it in the hole, and it expands & seals. Just remember you want it tight but not so tight that you snap the nut. Clean hole good prior to install. Will save you lots of time and aggravation. If it is your block heater, just buy another the same, they are pretty easy too.
Now to the Caravan, click on link below and scroll down to figure # 2 and click on the picture, that is your engine. Where about do you see leak from (area) Maybe below # 9?
http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c1528003c50f

Most likly place is the bottom of the water pump which happens when the pump is going bad, or a hose. I would look their first. You may have to get it on a hoist or raise it up to look under it and see where it is coming from. 

Freeze plugs are usually on the side of engine block. If the freeze plugs leaking, it is a simple job to replace them without removing the engine. You should get under the truck to locate the source of leaking antifreeze.