Home › Forums › Stay Dirty Lounge › Service and Repair Questions Answered Here › Engine "breathing" through oil filler hole when open. › Reply To: Engine "breathing" through oil filler hole when open. October 26, 2020 at 9:37 am #986829 David ErhahonParticipant In another forum, people say such crankcase high vacuum is normal in Honda cars. Nevertheless, I will perform the compression test when I get the tool.