u/Key-Ambassador-6629 — reddlx

My 2016 Mazda 6 recently broke down and would not start initilly after it shut down now it will start and make noises for a couple seconds before shtting off again. Initially, the car made a loud clanking noise before the engine cut out completely. It is not throwing any codes.

Symptoms & Diagnostic Steps Taken:

Initial Failure: Car stalled after a clanking sound.
Sensors: Replaced both the Crankshaft Position Sensor and Camshaft Position Sensor.
Inspection: I pulled the valvecover to inspect the valve train and don't see anything wrong with it.
Current State: The engine briefly ran but produced a persistent, high-pitched squealing noise and has rough idle.
Testing: Removed the serpentine belt to rule out accessories (alternator, AC compressor, etc.), but the noise persisted from within the block.

Current Verdict: I suspect the motor is shot, possibly due to a spun bearing or internal mechanical failure, and I am considering a replacement.

Question: Has anyone else with the SkyActiv 2.5L experienced these specific symptoms (clanking followed by a no-start/squeal)? Is there anything else worth checking before I officially call it a "dead engine," or is this a known failure point?

Edit: Car only has 117k miles on it