Hi all.
What exactly are the functions of each of the ports 7, 13, 17, 20 at the reservoir 18 ?

How come '13' gets in by the cap thread, how is the interaction there ? When-why-how-what
'7' and '17' connect directly to the reservoir under coolant level, right ?
'20' vents at the rated cap pressure and nothing else, right ? '20' is above the coolant level line, right ?





(Image borrowed from the net)

 

Something I can answer

13 is the coolant/air return basically as your system pressurizes then cools the air or coolant has to get back in the reservoir that hose does it. It it usually moves very little.
20 is just the overpressure vent hose

 

7 warms up the throttle body. Not sure what 17 does. They both route coolant which is why they are below level I presume. I am not the coolant routing expert.

 

#17 is the main coolant hose connection in which coolant from the reservoir goes directly into the main lower coolant line.