Thanks guys for your replies; I am a new guy to FMCA and appreciate your help. I did get in touch with Lippert and they were nice, appearently the resivor cap is a vented cap and he told me to check that, which i did and is ok as far as i can tell. My plan now is to lower just a little the fluid level and replace the o ring gasket and see what happens. Sorry for not mentioning that I have a 2017 Sportscoach 404 RB. JACK