What is a seized engine?



I was watching a video on Dunkirk and was told that soldiers would run truck engines dry to cause them seize and rendering them useless to the Germans. What is an engine seize? Can those engines be salvaged? Or would the Germans in this scenario know it’s hopeless and scrap the engine completely?

In: Technology

When an engine runs without oil, the friction causes it to get extremely hot to the point that internal parts break or, in more extreme instances, the metal pieces weld themselves together.

The end result, though, is a 100% dead engine that can’t be fixed in any practical sense of the word. (Sure, it could stripped down piece by piece and completely rebuilt and have any damaged components sorted out… but that’s not practical in the middle of a war. And it’s usually costs more than it’s worth.)

Inside of an engine, you have hollowed out tubes and cap-like pieces that fit within these tubes. [Image.](https://upload.wikimedia.org/wikipedia/commons/5/51/Internal_combustion_engine_pistons_of_partial_cross-sectional_view.jpg) Crucial to the operation of the engine, these cap-like pieces must be able to slide up and down constantly. They run pretty much the full length of the tube multiple times a second. If even one of them stops, the engine cannot run, as they are all coupled together.

From here on, the cap is called the piston, and the tube is the cylinder. The piston and cylinder must very tightly fit one another. The piston is just barely small enough to fit within the cylinder. Should one of the pistons be damaged in such a way as to begin to grip the walls just right, it can easily become wedged. It will immediately stop. Since it is physically connected to the other moving parts of the engine, and they are moving quite fast, the forces jamming it in are absolutely huge. Things bend, things break, and the piston can become effectively fused to the cylinder. It would be far cheaper to build a new engine from scratch than to repair this one.

Running an engine dry (of oil) causes moving parts to overheat, warp and bind (seize). Essentially the crankshaft no longer turns. It is sometimes possible to recover but it requires a LOT of work, replacement parts and a good workshop – it isn’t something that can be done in the field so it renders a vehicle stuck on the road useless.

An engine is usually seized when it locks up due to a number of reasons, but in this case they’d drain the oil and coolant causing major damage. First the engine overheats and causes the block and heads to warp making it pretty much unable to seal between the parts. The cylinders will warp and not allow for the pistons to properly move nor for the rings to keep the combustion chamber separate from the oil, which is now mixed with any coolant left in the system. Narrow clearance areas like bearings also warp and now provide much more resistance. I’m sure I left some out, but also the main forms can outright crack. Metal against metal needs lubrication. Things like main bearings and rod bearings are simply metal separating two other metals.

In short it’s not worth rebuilding versus new equipment and sometimes not even possible at all.

Engines have moving parts, which is why they need oil to lubricate them.

One job of the oil is to dissipate the engine heat. If an engine is drained of the oil, then the heat that gets created by it expands the metal parts until there is no space for them to move about.

When these parts rub against each other, they grind together and fuse, or seize up. Then the engine is useless until it can be taken apart and rebuilt properly.

A seized engine is an engine which does not turn over any more. Even if you try hand cranking them or bump starting them the engine will not physically be able to turn.

In an engine there is a lot of metal components moving against each other with a thin film of oil between them to slide on. But if you remove the oil from the engine the metal will just scrape against each other “dry”. This will make a lot of heat and scrape up the metal. The heat weakens the metal causing even more damage and may also warp it. The end result is often that the metal pieces in the engine which is supposed to be a tight fit is now crashing into each other and the engine does not turn over.

If this happens to your car and you notice the oil pressure light turn on and immediately pull over and stop then you might not have damaged any components at all. And even if you did some damage it is possible to swap out those components of the engine and it will be good to go. And in the late 30s swapping engine components were a regular maintenance task so these components would have been readily available. The problem was that most of them were back in the UK as German and French cars were built with different engines then the British cars. In addition the cars were run dry as long as possible which would have likely damaged a lot of the internal components. They might even have damaged the engine block which is the biggest component of the engine. At that point it is cheaper to just get a new complete engine then to replace most of the components of the old one. In any case it would have been a lot of work for the mechanics. So I doubt any of the trucks that were run dry and left on the beach would have ever been operational again. They might have been used for spares to help maintain the trucks that were abandoned intact. It is also possible that some Belgian farmers would get a hold of a few of the trucks and spent a good amount of their spare time getting one of them working again.

Ok, let’s try this:

A seized engine is a broken engine. Normally, it means that the pistons have jammed within the cylinders (the two parts that contain the exploding fuel) and the engine is locked in place.

Yes, they are salvageable, but thats expensive, time intensive and difficult. An advancing army does not have any of these luxuries.

The Germans would have tried to fire up the trucks that got left behind and use them, only to find they won’t start. Knowing likely what had been done to them, they would have had to proceed without them, rather that waste resources and time on them.

Denial of surrendered equipment is always a good idea in wartime.

This is the first post I’ve ever seen where the first ten responses are all correct and not jokes.

Yeah to make it really simple: no oil or coolant in a box filled with explosions (an engine) = extremely hot metal gouging itself apart and welding itself solid simultaneously.

An engine is seized when it is mechanically impossible to rotate its crankshaft. In the scenario you described, seizure was achieved with excess friction because there was no oil to lubricate the metal-on-metal movement. The pistons probably expanded and warped, becoming wedged inside the cylinders. Besides that, connecting rods and crankcases usually break. When the engine is seized in this way, repair *might* be possible depending on how extensive the damage is, but usually it’s so severe that it is both not repairable in the field and more expensive to repair versus replacing outright.

Engines move very fast. When metal moves fast it gets hot and it gets slightly bigger. Oil stops the engine from getting too hot. The space in an engine is so tight that when you take away its oil, the metal expands and gets stuck together.

Someone drained the oil out, and the metal parts in the engine get stuck together through heat and friction. They expand into each other and is irreversible to fix without some serious, time-consuming work.

Seized means stuck. They make the engine stuck so it doesn’t move anymore.

In most cases doing it this way, the engine is no good anymore. Because it damages the block that everything on the engine is attached to!

Inside an engine there are pistons that reciprocate (move up and down) within a cylinder. Due to the large amount of heat produced by engines from combustion and rapid movement of the piston inside the cylinder, engines must use a lubricant such as engine oil in order to stop the pistons from essentially melting to the cylinder walls.

There are two types of engines, 4 strokes and 2 strokes. While both use oil as a lubrication, 4 stroke engines store oil inside what’s known as the crank case near the bottom of the engine. Oil is essentially shot into the cylinder from the crank case while the piston is moving up and down in order to lubricate the cylinder and allow the piston to move freely with very little friction. The oil then drains back down into the crankcase and is reused.

2 Stroke engines work very similar but rather than storing the oil inside the engine, the oil is usually mixed together with the gasoline. When the fuel valve opens, the engine is not only receiving gasoline for combustion, but also a portion of oil mixed within the gasoline to lubricate the cylinder. The excess oil is burned off during combustion.

For both engines, oil is a necessity. Without it, the pistons won’t move for very long before they become stuck inside the cylinder or what’s known as becoming seized. This renders the engine useless. Generally, the engine is destroyed if it becomes seized as parts become almost welded together inside or break apart. In rare cases, the engine may be salvageable if it wasn’t run completely dry of oil or the engine was shut off before it fully seized. However, this almost always results in scoring on the inside of the cylinder and piston. When scoring occurs, the piston no moves as fluently reducing power and oil can begin to leak between the scars inside the cylinder. This is fixable though, usually with a replacement piston and boring out the cylinder to a slightly larger size to get rid of the scarring inside the cylinder. This becomes more of a hassle the more cylinders you have.

Jesus, I think I made this too long to actually be of any use lol. Anyways, in conclusion, don’t run an engine without oil or it will seize and become useless. The Germans, or anyone for that matter, would most likely scrap the engine as it would not be worth the time or cost to try to repair a seized engine, especially in the middle of a war.

Metal on metal needs lube. Without it the metal gets too hot and expands. That means your motor is fused together. Congratulations on your new boat anchor