MCI-9 Coolant Level

[Kwajdiver]

This may be a silly question, one I should have ask when I purchase this coach.
How do I check the water in the cooling system?  The manual says to check the water lever in the surge tank via a sight glass. Manual also states the filler neck and pressure release valve are mounted behind the access door on the right read side of the coach.

Nope, do NOT have it.....   I can see the bottom third of the surge tank.  On the right side of the surge tank, there is a short filler neck, above the blower.  It would be possible to add water, but not monitor it.  I believe this coach has had a rear cap put on it.

Also, on the rear left, behind the tail lights, is a mystery tank, which is empty.  The filler neck for said tank is on the left side of the rear doors.  What is this tank? 

Why over my head,,,,, but learning to swim....

Thanks for the input....

Bill