Create A PCV Valve Bypass System

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User How ToThese instructions show the steps needed in order to introduce a filter into the PCV Valve hose.  This modification will keep your Mustang within emissions standards in any state and will also prevent oil spray from entering back into the air intake manifold and gunk it up.

Submitted By: MarvinMyCat


{mosgoogle}Before emissions were introduced a breather valve that vented to the outside air was the predecessor to the PCV Valve.  Also note that this air now is metered due to emission standards and supposedly the oily air is filtered and returned back into the crankcase to be consumed by normal combustion process.  With the problems that have been reported by, this modification should help keep the manifold clean, and free of oil.

One modification includes the introduction of a "drip can" into PCV Valve hose, but I don’t feel that this would be the optimal way in preventing oil from re-entering the air induction system.  This can be accomplished by the use of a dual inlet can with a filter contained within the can.  The inlet hose should be placed at the bottom of the can, and the outlet hose toward the top so as to prevent a can full of oil letting the pool of oil injecting itself through the hose and straight into the manifold.  This modification would also require replacing the PCV Valve hose with a much longer one, and attaching two elbows to allow the drip can to catch the oil properly, and for the can to hang correctly after using a fabricated brace for ensuring there are no spills.

Another option is to just attach breather caps to where the PCV Valve is located.  The drawbacks to this are that the filter in the breather can get clogged with oil, or leak onto the rest of the engine.  Breather caps also require removal for inspection to make sure that they allow for easy airflow.  The end that the PCV Valve hose connects into to, on the other end from the PCV Valve, would have to be capped off as well.  Another draw back is when one runs the air conditioning and doesn’t have it set to “Max.”  When not using the Max setting, air is drawn directly from the engine bay and forced into the cabin, where it will start to stink.  I’m not sure if the heater option would have the same effect, but I am guessing that it would when set to draw in fresh air.  Lastly, not having the metered air return back into the manifold would cause your “check engine” light to come on, or your computer to throw a code.

Another breather cap option is to remove the valve cover oil fill cap, and affix a breather cap onto the end of that.  This would require capping the PCV Valve and hose end off.  Again, this could cause the cabin to stink again when using the environmental controls, “check engine” light, and computer codes.  It is also not emissions legal.

Categories: Mustang Tech

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