My heating coil was bent. Should it be replaced?
If the heating coil belongs to the landlord and it is still functional (it heats the apartment when needed, without leaking, etc.), you really don't have any reason to "make" your landlord replace it, and making a great fuss about it would put you on the short list for not getting your lease renewed with any sensible landlord. 

It's their property, if their chosen fix for the heater they own in the apartment they own is to bend it back into shape, you are merely a tenant who can choose not to renew your lease if that sort of repair is somehow offensive to your sensibilities. I don't think you'll have any luck from a legal standpoint trying to break your lease over it.