My son has a 2011 4x4 diesel Holden Colorado and had the front crankshaft seal replaced as it was leaking. The next day whilst driving the engine developed a knocking noise, leaking oil and a wobbly harmonic balancer. We spoke to the mechanic and explained what had happened. Without seeing the vehicle, he indicated that it could be that the crankshaft had broken. Would this at all be connected with the original replacement of the front seal?
It’s very difficult to diagnose problems over the phone, just as it is via this website. But, I’d be taking the vehicle straight back to the mechanic in question, because whatever is wrong is going to be fairly major.
In the majority of cases, an engine with a broken crankshaft won’t run. In fact, it won’t even turn over. Sometimes, it will still run, though, and the symptoms you’ve described are spot on for that. Either way, a broken crankshaft is one example of what’s called catastrophic failure and a new crankshaft (at the very least) is the usual result.
But those same symptoms can also be the result of a loose harmonic balancer. And here’s the clue: The harmonic balancer has to be removed to replace the front crankshaft seal (which was done the day before the problems started). If the balancer is not reinstalled correctly, it can start to wobble, tear up the new seal and make all sorts of noises and vibrations. The bad news is that often, the wobbling balancer destroys the end (called the snout) of the crankshaft in the process, so even though the crank is not broken or snapped per se, it may still need to be replaced. It does seem like a fantastic coincidence that the balancer started wobbling the day after it was removed and refitted. That said, if the crankshaft has failed, then a coincidence is precisely what it might be.