* No start: This is a very common symptom, but could be due to many other things.
* Loud, unusual noises from the engine: A broken timing chain will make a very distinct rattling or knocking sound, especially during cranking. However, other engine problems can also create loud noises.
* Backfiring: A severely damaged or broken chain that causes significant valve timing issues can lead to backfiring.
* Lack of compression: A broken chain will cause the valves to be out of sync with the pistons, which can lead to low or no compression. You'll need a compression tester to check this. Low compression in several cylinders strongly suggests a problem, but not necessarily a broken chain.
* Inspection of the timing chain cover (if accessible): While this won't tell you if it's broken *inside* the engine, you might be able to see signs of significant damage to the cover itself (like significant dents or cracks) which might indicate something catastrophic happened within. This is a very weak indicator, though.
Why you can't be sure without disassembly:
The timing chain is entirely enclosed within the engine. You can't visually inspect it without removing components like the timing cover, and possibly even the crankshaft pulley. Even then, a small break might be difficult to spot.
In short: The symptoms listed above might *suggest* a broken timing chain, but further diagnostics (compression test, possibly even engine teardown) are necessary for a definitive diagnosis. If you suspect a broken timing chain, it's best to consult a mechanic to avoid causing further engine damage. Attempting to run an engine with a broken timing chain can lead to very expensive internal engine damage (bent valves, damaged pistons, etc.).
