[thstone]

So, the answer is no, there are no warning sounds. By the time the engine sounds bad (typically it sounds like nuts and bolts rattling around in a coffee can), its past the warning point and the engine is already self-destructing.

Once it sounds bad and the damage has begun, metal particles have already circulated into every friction surface in the engine and started to cause significant damage. The only next step is to tear it down.

Now, the percentage of IMSB failures is very low so you need to keep the risk in perspective, but once the engine sounds bad, its done.