Engine explosions are a pain. The reason I take out the head, is because thats the quickest and safest way to quickly take a tos down. (and its kinda fun seeing a headless titan on scanner window, especially if you have no scan and you didnt blow anything else off. You look at it and think "gee, he aint dead yet" then you realize something's wrong with the picture, and notice that it DOESNT HAVE A HEAD.)
Engine explosions are supreme pains, the damage is negligible, as long as you're not using light or recon and you havent been engaged in bloody battle for the last 100 seconds(i.e., all your armor isnt yellow or worse). but the heat... man, the heat is DEATH. Not just cause it shuts yer engine down, it also makes ammo explosions(which RAISE the heat back up), assuming you're packin ammo-using guns.
Although I must admit there are some times where you kill the engine, with no boom (not sure when this happens, seems like it happens when target titan isnt using much power, or is severly disabled but not dead (ie, one side's torso, arm, and leg are gone, but it still has that annoying tesla bolt on the other side.)
and theres something to having an entire black titan (which i did once without exploding the titan once, took forever)