Do a search on "oil check valve" to start. Also, look in the DIY section. Dave Morrison wrote up an excellent article on the procedure.

I do not know of a test, but I suspect you would need to take it out to test it, and if you are going to go that far, you may as well have a new, clean one ready to install. They are cheap compared to the time you are going to put into the job. And it is a messy job, I understand.

Have you changed your oil? I found that this helped the problem. I was not sure when the PO changed the oil in my car. Also, make sure your air filter is clean. If it is not, your engine will be straining to get air and will draw it from whereever else it can find it, i.e. up the drain tube.

Richard

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