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Concepts: Where exactly does the coolant go? "water jackets"?

I know the coolant gets pumped through the radiator for it to cool off.
But where exactly does this coolant flow around? I have seen the term “water jackets”…

What is the basic design? Some sort of shell?

Are there “doubled walled” cylinder walls that allow for coolant to flow past the walls of the “inner” engine?
This constant stream of “enclosing fluid” then wicks/dissipates heat away from these walls?

Anyone have a picture that would demonstrate these channels that the coolant flows through?

The engine block and heads have hollow spaces cast into them and yes the hollow spaces in the block do mostly surround the cylinders and are called the water jacket. You are also correct that the coolant takes the heat that is bring produced in the cylinders and gets rid of it into the air passing thru the radiator.
If an engine doesn’t have any coolant like small lawnmowers or old VWs or most motorcycles they have cooling fins cast into the outside of the engine and depend on the oil to help transfer the heat.

This may be useful:

The engine generates heat from both the combustion process and by friction. If the heat isn’t removed, it will warp the engine components, and the engine will stop dead. You are right that the engine is sort of purposely hollowed out with channels for water to flow through, picking up heat from both the cylinders and the valve train, and dissipating the heat in the radiator. The water also goes to the heater core for winter warmth to the passenger compartment. The water pump supplies the force to push the water through the various places it goes.

Can someone point out where the coolant flows in this photo?

Also, I think this topic relates to why a sign of a blown head gasket is coolant in the oil.

I see 3 vertical “tubes” on the side of the engine, and I see the hole leads to the top,
where the block meets the head (hence, head gasket).

So, does the coolant flow up these tubes from the block to the head,
and THAT’s how coolant will leak into the combustion area / oil when the head gasket is bad?

The coolant flows through all of wedge-shaped holes that surround each cylinder. Basically, all of the space between the outside surface of the block and the actual cylinder sleeves is full of coolant. Those two round plugs on the end of the block, and the three plugs visible on the side, all have coolant behind them.

The three tubes you’re looking at are likely the oil drain holes. The ten round holes interspersed between the coolant passages and the cylinders are for the head bolts.

Somebody who actually knows what they’re talking about will likely be along soon and give a more accurate answer.

Most of the engine heat is given off by the HEAD, which is honeycombed with water passages…The Triangular holes in the block line up with similar holes in the head(s). In the block you pictured, the coolant would exit the heads into the intake manifold where it’s flow would be restricted by a thermostat. When the coolant reached the desired temperature, the thermostat opens, allowing the hot coolant to flow into the radiator…Automotive water pumps can move a surprising amount of water…

On the side of the block you see the “freeze plugs”, round steel plugs that seal the holes in the block casting that were needed to remove the sand from the block when it was cast…In the finished engine, there is coolant behind those plugs…

I don’t know if there is still a version in print or if it could be found at a used book store, but I have an old “Readers Digest” book of car care. It is a big blue-covered book that has an amazing amount of info on how cars work, presented in a very easy to understand manner with really good drawings. While mine is out of date, the mechanical stuff mostly still applies. Engines haven’t really changed all that much in many years.

The cooling effect of oil is very important on air-cooled engines, but still important on water-cooled engines as well. You could think of it like this: The oil carries away a lot of the heat by direct contact with some of the hottest parts, and the coolant flowing through the water jacket cools the general environment, and indirectly cools the hot oil.

Here is the book. Only $4 shipped… Thanks for the tip.

The photo here

may be more easily understood. The water pump fits in the hole at the front.

Oh yea, great photo. So the coolant totally surrounds the cylinder walls. This must really be a closed system for the small water pump impellers to move that much fluid around…You’d think it would just splash around whatever fluid is next to it, but not exactly have it flow around an entire engine block. The channels must be really tight and restricted.

Model T engines had no water pump but they were water cooled. It isn’t necessary for the water to follow some intricate path around every square inch of block surface. Heat will rise. The earliest engines were water cooled but used no water pump or even a radiator.

Right, but modern engines are specifically designed to route the coolant through the radiator. It’s just seems amazing that a few little water pump fins can push fluid around the entire block and through the radiator… That’s a lot of travel…

That is the book! Like I said, it is a bit dated, but most of the info is still very applicable. Those little water pump fins are spinning quite rapidly and can move a heckuva lot of fluid. Water is incompressible, so if you move it, it will all move unless a passage is blocked.

The Model T routed the water through the radiator without a water pump. If physics interests you look here

If you live anywhere near Northeast Mississippi you might enjoy visiting here

this weekend. There will be dozens of the old flywheel engines, some larger than a car The festival is one of the biggest events in that small town which is “dry” and quite family friendly. It’s the kind of town where you might get arrested for public profanity.

And FWIW, water pumps don’t push water through the radiator, they draw the water out of the radiator. Pressure on the upper hose is from the expansion of heated water.

Another great photo

Are those non-interference pistons, b/c of the groove cut away for the valves?