Thanks, Buck... indeed it was plugged up with rust and a small drill bit twisted in by hand cleared out the hole. Then I blew out the vent hose with compressor to clean it out.

FYI...I suggest you all check this piece out if you have it. It should be VENTING. I had my axles out while doing my breaks only a couple of days ago, and put it back together. It was cold then. When I unscrewed this piece today to clean it out, a "wush" of air released when removed. That was just a difference of about 20* over two days (maybe more as sun was hitting axle) and it had that much pressure difference in it. Can only imagine when it gets hot under normal driving use and that vent is plugged!! CLEAN IT OUT!