How to work out if your engine is dead
Sometimes things don't go right, and we end up with an engine making unhealthy noises, or performing poorly. Marty recently went through this with his Levorg (CHECK THE VIDEO HERE) so I figured it was the perfect time to throw some advice out there for the people who are fortunate enough to have not grenaded an engine before.
As engines are made up of thousands of individual components, there are dozens of ways they can fail - from innocuous sounding rattles to giant kabooms that end with you driving over your own crank, there are many ways to hurt your engine.
The first thing to check is the oil level, and hopefully it still has good viscosity (that means it is slippery), and isn't contaminated, doesn't smell burnt, or have pieces of metal floating around in it. Sometimes and engine will keep running but there will be a death-rattle sound that rises and falls as RPM rise and fall - that is a dead main bearing and you're up for a full rebuild
But what about other engines that aren't running right, but don't have a con rod hanging through the starter motor? Start with draining the oil and inspecting it. Have a look at the drain plug and wipe a finger inside the sump - you're looking for metal paste.
You can also cut oil filters open and inspect the paper element for any metal shrapnel, metal paste or the like. If it is dry inside that is a huge red flag - it means your engine is pushing oil through the filter which could mean you've got a dead oil pump (and you'll be rebuilding your engine).
If there are no red flags in the oil put fresh oil in the car and start thinking about what the engine is doing that is causing you concern - if the car is down on power and blowing white smoke you should do a compression test or leak-down test to check for a blown head gasket.
You can learn a lot by pulling the spark plugs and checking for damage; listening for odd noises from the engine; looking for leaks while it is running; and looking for odd vibrations from the motor.
With Subarus most of these paths lead to pulling the engine out and tearing it down for a proper inspection. Ultimately a professional mechanic will tell you super-fast what has gone wrong but where is the fun and learning experience in giving it to someone else?