It's kinda weird you can get your mech to be overly glowing and yet nothing bad can happen. This ModTek mod changes that.
Ammo explosions roll a chance to explode every time your mech overheats, and they roll a more severe chance if you overheat enough to force a shut down.
By default, these values are 10% per box, and 20% per box respectively.
mod.json has some settings on how the chances work, and they should be self-explanatory.