[JFP in PA]

Originally Posted by mnracing

Thanks, Normally I find these things with a smoke test. I have been avoiding the AOS wrestling match. I have a new one sitting here so that's an option.

I'm not a fan of throwing parts at problems, so I usually diagnose a far as possible.

You can accurately test the AOS by measuring the case vacuum at the oil fil cap. An old oil cap, a barbed bulkhead fitting, a short length of vacuum line, and a digital manometer off Amazon creates a tool that will tell you what's what in about 5 min. without mussing your hair, and then you can test it anytime you want.