only very rarely have I experienced a caffeine crash -- when I've not been consuming much/any lately and consume a huge amount at once. I differentiate this from "caffeine withdrawals" because to me crash implies no dependency, just the comedown.
man though I did have to w/d off 350mg/day of caffeine recently and that sucked. I'm not sure exactly how bad it sucked because I was also w/ding off an amphetamine, an SSRI and an antipsychotic at the same time, but I attribute those deathly headaches to the caffeine at least.
symptoms include -- headache, exhaustion/fatigue, depression, irritability, insomnia despite a strong desire to sleep