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Discussion Starter · #1 · (Edited)
I normally change the PCV valve at 30,000 intervals. 20R engine

Just out of curiosity, I pulled mine (OEM Toyota), and tested it per the FSM. When blowing air from the crankcase side to intake manifold side, air flows freely.But when blowing the other way, intake manifold towards crankcase, NO air can flow. The FSM says that air should flow "with difficulty" in that direction.

Also, there is barely any rattle when shaken, as compared to the new valve (Standard Motor v168)- OEM PCV valves are no longer available.

I always thought that a clogged PCV would block flow from the crankcase to the intake manifold (leading to oil leaks and other problems), no? What ill effects would there be if there is a one-way blockage like I had? (24,000 miles since last replaced)
 

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That’s why it’s called a valve…Positive Crankcase Ventilation valve. It only vents positive crankcase pressure out to the intake, not the other way around. If the air flows in that direction, it’s fine. The rattle sound is just a quick check.
 

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Discussion Starter · #3 ·
That’s why it’s called a valve…Positive Crankcase Ventilation valve. It only vents positive crankcase pressure out to the intake, not the other way around. If the air flows in that direction, it’s fine. The rattle sound is just a quick check.
That's what I thought. There would only be harm if air (blowby) cannot escape from under the valve cover, not the other way around.
I'll clean the old valve with carb cleaner, and re-use it. The new aftermarket one is no where near the quality of oem. Thank you.
 
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