Hello, people who know about car engines...

Your own car or someone else's. One you have easy access to or is it locked?

Take off the radiator cap and throw it away.

Sugar in the gas tank?

Loosen the oil filter. That will slowly leak away the oil and overheat the engine.


Not that any service center ever did that to a car of mine...

Don't tighten the battery mounts down all the way. Also make sure the clamps are loose. Eventually what this does is disconnect the battery so it stops charging. And neither would necessarily be noticed in an inspection.

But one day the car just won't start.

I once had the fuel lead come loose on my old ford fiesta. A clamp failed and the pipe eventually worked it's way off whatever it was attached to. With no fuel, the car ground to a halt. Of course, you risk setting the car on fire.

Oh yes, that reminds me of another possibility. If you can find a place in the fuel line where wear would normally happen, and increase that wear into an actual hole, the fuel mix will become too lean (because it will get too much air) and the car will start to stall out. This is lots of fun at an intersection where you're in front of other traffic and heading uphill at a traffic light. Oopsie!

Loosen the distributor cap on an older car
Remove the little round rubber bit on any vacuum hose that provides a tight seal; the hose will loosen and sometimes just removing the seal will let in enough air.

The rubber parts on hoses that serve as seals rot; they're self-consuming artifacts because the chemicals they're made from cause them to decompose over time.

Perks said:

This could be very good.Do we know what pipe and clamp we're talking about?

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It was the pipe into the fuel injector. The clamp where it met the fuel injector failed.

I got my oil changed one time and they forgot to put the oil cap back on. I managed a 1000 mile trip before I realized it. Somehow the cap was still sitting on top of the engine so I popped it back on. I checked the car as soon as I could and I was a little low on oil and there was some oil splashed up on the bottom of the hood.

It might not be plausible, but if I had driven though bad enough weather like that I might have gotten some mud and gunk from the road down into the engine causing a break down.

Vacuum hoses as mentioned above. They degrade on older vehicles and break off, and sometimes some of them will stop the car from running. A mechanic could have snagged one working under the car or near the tires and it broke off the rest of the way while driving.

Make it a TVR. Those spend more time off the road than on it (yes, I speak from bitter experience). They routinely do exactly as you describe in your original post

Slice partway through any belt. The farther the better, depending on when you want it to break. No idiot light in the world world will turn on to warn the driver. And, there's no one to blame, because it just happens.

Is it going to be intended sabotage by the mechanic or an accident? A lot of things could happen either way.

CetiAlphaVI said:

I got my oil changed one time and they forgot to put the oil cap back on. I managed a 1000 mile trip before I realized it. Somehow the cap was still sitting on top of the engine so I popped it back on. I checked the car as soon as I could and I was a little low on oil and there was some oil splashed up on the bottom of the hood.

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I forgot to put on/tighten my oil cap once after checking/adding oil. The oil sloshed onto the manifold and started a fire. I was lucky and managed to beat the fire out with some of my clothes - I'd just returned from doing laundry.

SWest said:

Loosen the oil filter. That will slowly leak away the oil and overheat the engine.


Not that any service center ever did that to a car of mine...

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Incidentally, if not caught in time, this one will pretty much kill the engine permanently.

Perks said:

So, if a serpentine belt breaks, does the car just grind to a halt wherever it is?

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It can do more than that. I had a belt break on a Mitsubishi Eclipse. Spark plugs shattered and pistons cracked when the cams lost sync.

Oh, ways a car can screw you over.

I've had a battery with a loose terminal, the car would just off and not restart until the terminal got wiggled, but then would run just fine.

A bad fuel pump relay has done the same, but I was able to swap it out with the wiper relay once I narrowed it down.

A failed radiator hose brought me to a stop in a cloud of steam. A hose failing can't be fixed by duct tape it seams.

I've had belts fail on me ranging nuance (AC pump) to terrifying (power steering).

Yea, I've had a few cars where the wheel fell off. Once literally.

If the car has just been in for an oil change - just fail to screw the oil drain plug back in properly. Depending on how long you want the car to run before the engine blows up, either leave it out entirely (probably won't get more than a couple miles, if that) or leave it loose/cross threaded enough to leak (could possibly take days depending on just how loose - but driver might notice the puddle under the car before it broke down.)

I agree with the oil filter/drainplug. I had an oil change performed at Walmart once. The oil psi light came on before I got home, inside ten minutes. They overtightened the drain plug, and cracked the seal on it. It lost around three quarts inside ten minutes. It might have ran for a few minutes or even hours after the oil went away. The only reason I knew anything was wrong, was the oil light.
Which means the saboteur would also need to make the light malfunction. Most new cars have a resettable oil life meter, which has to be reset from inside the car. This would give them an excuse to be inside the vehicle while thye disable the light.

Hope this helps

On the other hand, not everyone pays attention to warning lights. Or, they may THINK they know what the light means - for example, there are a lot of things that will trigger a "check engine" light, including a loose gas cap. If mechanic says "don't worry about the light, that's just because..." and gives some reasonable sounding excuse, most non-car folks would buy it.

Of course, it doesn't matter if the light is on or not if they get the oil change and then drive off into the wilderness where there's spotty cell service.

Good point. I have had cars with a permanent check engine light.