I cannot find a particular documentation about golem senses, what will happen when a golem is inside a Fog cloud spell? Can he see and hear normally? Is its line of sight blocked? In our case we are dealing with an Iron golem.
Golems are constructs. Per the general construct rules (unless the specific golem writeup overrides it) they therefore have darkvision 60' and low-light vision.
I'm not sure how you are not finding this, as it's in the stat block for every creature under Senses, right after the Init in the top section of the monster stats. For example:
Iron Golem CR 13 XP 25,600 N Large construct Init –1; Senses darkvision 60 ft., low-light vision; Perception +0
They also have immunity to mind-affecting affects including illusions of the pattern and phantasm types, and immunity to spells in general, but fog cloud is a SR/no conjuration (creation) spell and thus the fog it conjures blocks sight. (Because "An iron golem is immune to spells or spell-like abilities that allow spell resistance.")
So no, an iron golem can not see through a fog cloud (and it can slip on grease). Those are actually some of the basic standbys to fight them.