engine coolant reservior

Before you do that, go over to the Monaco site and do a search for coolant reservoir and pressure caps. Most of those tanks are of a "nylon/plastic" type of material and are subject to rupture if pressures get to high. On my 05 ISL400 in a dynasty, the cap was 8 lbs as I remember. (now sold). In any case, at least give Monaco a call with your coach id number and ask what was original pressure cap supposed to be.

http://www.irv2.com/forums/f115/

check with knects if they don't carry it they can order one one for you.
at least they found one for me a couple of years ago
they are available on ebay also

I would think a 16 lb. cap SHOULD be OK but have you tried a dealer for that engine/chassis manufacturer?

Sure you can