Broken crank bolt
I had this happen...twice. Neither was covered because I was over my 100K mile warranty.
The first repair was by the book. The broken bolt was removed from the crankshaft and replaced with the standard Kia bolt, all to the tune of $938. When it happened again, the first mechanic refunded every penny without a fight (can you believe it?) the second time I took it to a different mechanic who wanted to do the same repair. I put him on hold, and began doing a little digging.
It turns out that Kia re-purposed a crankshaft, pulley, and harmonic balancer already in use in other models, as car makers often do. In order to make it easier to remove the crankshaft pulley for future repairs or service, Kia designed a mutant bolt with an extremely lengthy, and HEAVY head (heavy being the operative word), as in about 8X heavier than the standard. The problem was, they did not increase the diameter of the bolt to compensate for the significant increase in weight, so when the engine operates at 4K-5K rpm’s for 100K miles, it's only a matter time before the bolt shears off.
So what was the repair? I had a machinist drill the crankshaft, pulley, and harmonic balancer, increasing it by 1/8”. Drilling the crankshaft required removal of the grill to gain access, but it was MUCH cheaper than removing the crankshaft. He used Some type of laser system to assure he was dead center.
I’ve had no further issues. I was concerned at first about the drilling of the crankshaft, because if it had been off, that would’ve created a whole new set of problems, but he was spot on. The new bolt was a hardened bolt with a normal head.
Why Kia felt they needed a mutated bolt, I do not know. It certainly couldn’t have been only to make service or repairs easier, because isn’t that what Deep we’ll sockets, and socket extensions are for? If anyone knows, please share the info.