After my rear cam plug blew out the first time, I did what I thought was a thorough job of renewing the PCV system - I removed and cleaned the oil separator box as well as the flame trap, replaced the small vacuum hose going from the flame trap to the intake manifold, and plugged the two evaporative emissions vacuum lines coming off the throttle body (old ones both were leaking badly - this is a temp fix to seal the vacuum leak until I figure out the problem). After I did all the work, my rear main seal appeared to start leaking, and then the cam plug blew out again.

Anything I might have overlooked? I think I have high crankcase pressure but I've about run out of ideas.

i'd replace the oil seperator. only about 40 bucks or so. they tend to plug up and breathe as well as when new. good luck, chuck.

Have you made sure that the small hose leading into the throttle body is clear? The nipple on the throttle can become clogged internally so that it is not actually getting vacumn to the pcv system.

Two things:

1) You definitely need to find the cause of the positive pressure -- you should have a slight vacuum (viz., the old oil fill cap test, leaving it on loose and seeing that it's held by a slight negative pressure in the crankcase).
I'm afraid I can't help with this.

2) [Let me preface this second comment by saying that I'm not sure if you have the newer engine that I'm thinking of. I've got a '84 B23F as well as two '93's with the B230F, but I'm not sure if the B230F appeared in '85 -- are you sure that you have the B230?]
Anyway, assuming that you do have a B230F, there should be two bolt holes on either side of the rear plug of the valve cover, which you refer to as the cam plug. To keep the cam plug from blowing out again, as you report, IPD sells an inexpensive kit consisting of a metal plate and two bolts. You can place the plate across the back and fasten it with the two bolts. This will prevent the cam plug from being blown out again.
[Others on the list will no doubt also report that you can make this kit yourself -- but it's so cheap, why bother?]

Anyway, No. 2 doesn't cure your problem, and you can damage other seals if you don't promptly find the cause of and correct the pressure -- this should be your top priority. No. 2's "anti-blow out" plate is only an interim solution to an effect of the problem.

Good luck.

Thanks, Ken.

Yep, '85 was the first year for the B230F, which was used all the way up to '93. The newer style headlights, seats, etc didn't come until '86.

I did try the oil cap test, but results were inconclusive. It was hard to say whether the cap was "sucked on" or not.

I've also seen the cam seal retainer, but don't like the idea and definitely think I have some excess crankcase pressure to deal with first.
--
85 245 DL - 91 Mazda MX6 Turbo

Check the PCV vacuum with the "palm test", it is more sensitive than the filler cap test. Do it with the engine cold. With the engine idling, cover the oil filler hold with your palm and feel for a slight vacuum. Be certain.

The PCV system at idle gets vacuum via the smaller hose from the flame trap housing which connects to a brass fitting on the intake manifold. That fitting clogs easily. Pull the hose, unscrew the fitting and use a 3/32 inch drill by hand to clean it out. (Removing the fitting ensures no crud in intake manifold.) Reassemble and try the palm test again.

Get the plate across the cam cover/plug ASAP. Yes, it won't solve the overall pressure problem, however it will keep you from experiencing a catastrophic loss of oil and subsequent engine damage. Leaky seals just leak, seldom actually blow oil out.

Good Luck,

Bob

:>)