PCV Valve Vacuum Bypass

[rogue9]

If you removed and capped the vacuum provided by the intake manifold for the pcv valve and ran a hose from the pcv valve to just a filtered bottle to allow pressure to escape (pcv valve still in place,) would you harm the engine? The breather would still be connected to the air intake/filter and the system would still be "closed" by having a filter at the end of the new pcv hose.

In theory, any pressure build-up would be pushed through the pcv valve to the filtered end and the breather hose would still be connected to the air intake, taking in replacement air.

Thoughts?

[centralcoaster33]

According to GM Research Laboratory, about half of the cars hydrocarbons come out of that valve. That is, half of all of them, before having a cat or Evap or any other emissions device added. So, half of everything if your car ran in it's dirtiest state, no emissions equipment. The PCV was one of the first emissions cleaning devices. You want to route that stuff into your intake, which is what your OEM system does. If you cap the vacuum, then you only have the pressure of the crankcase to open the valve. I'm not sure, but figure it would be harder for it to open if not assisted by some vacuum. You may be reducing the lifespan of your oil. It sounds like you want to vent your PCV to atmosphere and have a small oil catch on the end of that and you leave alone the breather hose. Is that right? I think you are merely gaining more SMOG for your environment. No power, no cleaner intake, no improvements, just more pollution... I think. Why do you have this idea? (simple honest question, no implication or inference)

[rogue9]

PCV is pumping oil at an alarming rate into the intake. I know this is a symptom of another problem but to get the engine cleaner I have to operate it. To do that, I can't be burning oil/blowing smoke screens. i asked because I am doing this temporarily until I can install an oil catch can. Then I will connect it back to intake as before. So would it hurt the engine to drive it with a setup like this for say 2-4 weeks?

I do appreciate you taking the time to respond and am looking forward to your reply.

[centralcoaster33]

Okay, yes it will work as you described. Yes, you want to deal with the underlying issue asap. In the interim, you could get a small plastic catch can/ bottle and just put it into the hose from PCV to intake manifold. It would be a small bottle with two hose lines in the lid and you just run it inline, no plugging the intake side. That would maintain the vacuum and catch any oil before it goes to the intake. I don't even think the bottle needs to be filtered. Putting either on (inline or dead end) would also enable you to measure just how much oil makes up the alarming rate. You might want to track your mileage while you do this so you can get an idea of the rate of oil per miles driven.

[whizkidtn]

I would suggest you install a well rated Oil Catch Can (OCC) in-line from the PCV valve to the intake manifold port. That way, the nasty stuff you really don't want getting onto your intake runners and intake valves is greatly reduced, the emissions part is still satisfied as hydrocarbons are still burned up (or drained out of the OCC every few thousand miles) and the PCV system itself works as the OEM designed it to which is to help keep the crankcase vapors with cross-flow ventilation at bay and keeping the oil cleaner as well. I've gone to a similar system for my '12 Kia Optima 2.0L turbo with very good results (it is a GDI type engine).

[rogue9]

Sounds great. I'll post my findings.

[rogue9]

Well, after using it for a while, the catch can did not solve the problem. I found a video on youtube regarding defective valve covers and investigated the idea that the sludge in the engine from sitting so long partially blocked the PCV system. After researching, I purchased a new OEM NISSAN valve cover and replaced it, along with the PCV valve and gasket (PCV came with cover, gasket is OEM Nissan as well.) Problem solved. Over 200 miles and no smoke. Thanks for the help guys! I appreciate it.

[centralcoaster33]

Thanks for the update. I'm glad you've got it up and running properly!