How To Create A Bypass For Your Pcv System

Discussion in 'SN95 V6 Mustang Tech' started by marvinmycat, Dec 15, 2003.

  1. These instructions show the steps needed in order to introduce a filter into the PCV Valve hose. I did this on my 1998 3.8L Mustang - if there are any changes or modifications that need to be added for the 1999+ crowd, please chime in after this post! This modification will keep your Mustang within emissions standards in any state. This modification will also prevent oil spray from entering back into the air intake manifold and gunk it up. Understand that before emissions were introduced a breather valve that vented to the outside air preceded 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 people with nasty manifolds, 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 that the can does not tip in any direction compromising the effectiveness of the can system.

    Another option is to just attach a breather cap to where the PCV Valve is located. The drawbacks to this are is 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, the intake manifold, 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 that goes into the intake manifold. Again, this could cause the cabin to stink again when using the environmental controls, “check engine” light, and computer codes. It also is not emissions legal.

    The only option to actually deleting the PCV Valve would be, in the previous two options, would be to run a line down toward the ground where the oil could leak right onto the road way. This wouldn’t be the most environmentally correct way of doing things either.

    The next option, and most expensive one would be to acquire a fixed or modified valve cover that has had the baffles corrected that would prevent any oil from passing through the PCV Valve.

    The last option is to insert a fuel filter along the PCV Valve hose where it will filter out any oil that is sucked into the line. This would also allow the car to stay within emission standards as well as prevent the manifold from becoming gunked up with oil.

    The parts needed for this project can be bought from AutoZone for less than $25.


    Spectre Clear View Universal Fuel Filter..................................p/n 2369
    Spectre Clear View Replacement Element Filters.......................p/n 2358
    Tridon Clamps 5/16” – 7/8” range..........................................p/n CD-6
    Two zip ties around 2” long – your choice of colors
    Deutsch PCV Valve (optional)................................................p/n PCV188
    One foot of 3/8” fuel line (optional – see instructions below)
    Two feet of 3/8” fuel line (optional – see instructions below)


    Measuring tape or ruler
    Pipe cutter or metal hacksaw
    Sharp box cutter
    Flat head screw driver
    Small Philips head screw driver
    A miniscule amount of motor oil (lubricant)

    Pics of the parts minus the fuel hose and zip ties:


    The reason I chose the clear view fuel filter was so that it would be easier to inspect the canister and fuel filter element without having to open it up every time. The replacement elements are not required for this modification, but will be needed when the original fuel filter is clogged or nasty.

    The below diagram shows the location of the PCV valve ON A 4.6L ENGINE, which we will keep for this modification:


    The two pictures below show where the PCV Valve is on a 3.8L engine:
    The PCV Valve is located on the rear portion of the passenger side valve cover.

    This one taken while standing next to the passenger side front tire. Red arrow marks the spot.

    The next picture shows where the other end of the hose goes into the intake manifold. The yellow line shows the path of the hose, and the big red “X” shows the intake manifold itself as the picture is overexposed.

    The next step should be to disconnect the battery cable. Now remove the PCV Valve itself with the metal hose attached to it. Just pull it out of the valve cover, as it will come out very easily. Now reach behind the intake manifold and pull the metal hose back toward the firewall. This too, should come out with minimal effort.

    Lay the entire assemble in front of you for the next step. This is the 3.8L assembly. 4.6L guys should have a valve with a hose coming out of it.

    The PCV Valve is on the left side, and it is nasty. Here, you can either decide to keep the old valve or go with a new one. I went and got another one as mine is five years old. See below for nastiness comparison:


    This next picture represents the correct way in which to install the fuel filter, as it is a one-way design. The filter sits toward the outlet side, marked on the housing by the words, “OUT” on that side. The inlet side, away from the filter, is marked by the words, “IN” on the end of the filter housing. The “IN” side should be connected to the hose coming out of the PCV Valve, the "OUT" side should be facing the manifold. Blue arrow indicate the direction of flow. See below:


    Next, examine the rubber hoses and make sure that they are not dry and cracked. Also make sure that they are not shedding black stuff all over your hands while you are handling them. Any of these problems indicates that it would be a good idea to go ahead and change them with the optional fuel filter hose purchase.

    Next, decide which of the fuel filter vinyl connections will fit best inside of the 3/8” fuel hose. Guess what, the ones marked 3/8” fit best. Use a little motor oil to help seating and disconnecting the hose from the fittings. As you can see from the picture below, the hose is a little beat, and needs to be replaced:

    Now it is time to make a decision. Either you can use the two feet of fuel hose to replace the entire metal hose with, or you can custom fit the fuel hose onto two parts of the metal hose ends with the one foot section of fuel hose you bought. If you choose the first option (the easiest), then follow the next step. Retention of most of the metal hose follows after these forthcoming instructions. I chose to keep some of the metal hose, as I don’t know what hind of temperatures are generated at the back at the engine bay on a 3.8L engine, and I couldn't find any information on this.

    For the 4.6L owners, here’s your part, as well as the 3.8L owners who are going to replace the entire metal hose with fuel hose. On the 4.6L engine there is a length of hose that is wrapped in heat protection, do NOT cut this section of hose for this part of the procedure. For the 3.8L owners, take your two-foot section of fuel hose and connect one end back up to the manifold. Connect the other end back up to the PCV Valve and insert it back into the valve cover. You want to make sure the path that the hose takes will allow for enough room to clear all the hoses and wires, as well as give you a good spot to “mount” the fuel filter for easy viewing. The hose should take a nice path well above the manifold, and be toward the back near the firewall. This is where the 3.8L owners will “mount” the fuel filter.

    Both 4.6L owners, and 3.8L owners that will replace the entire metal hose line, follow this next step. Remove the hose again, and lay it out after the 3.8L owners have determined the correct length of hose for positioning the fuel filter, and after the 4.6L owners are happy with where the filter will lie within it's path from the PCV Valve and the manifold (if there isn't enough room for the fuel filter to fit on a straight-line to the manifold, the 4.6L owners may opt to loop the hose line around in a circle, or attach the fuel filter off to the side by use of a fabricated bracket - I don't have any experience with 4.6L engines so some feedback at the end of this post would be welcome!). Next, attach the vinyl connectors to the ends of the fuel filter with a crescent wrench. The connectors should screw in flush to the end of the fuel filter housing. Measure how long the fuel filter is with the vinyl connections attached at either ends.
  2. This measurement will represent how much of the existing, or new fuel line you will need to cut from the pathway from PCV Valve to the manifold. On the 4.6L engine, I do not know if there is room for this, but having a little extra length in the new setup should not make a difference. On the 4.6L line, make sure that you leave a ½” space of unprotected line on the side of the line from the manifold where the heat wrap is. 3.8L owners cut this much out of your length of hose to accommodate the fuel filter.

    Next, on both 4.6L and 3.8L engines, connect the ends of your lines to the new fuel filter, making sure that the direction of flow FROM the PCV Valve TO the manifold is correct using the “IN” and “OUT” markings on the ends of the fuel filter. In other words, connect the PCV Valve side of the hose to the “IN” side of the filter, and the “OUT” side of the filter to the hose going TO the manifold! Use a little oil so the hoses seat all the way. Optionally, you can use the small clamps on the hose ends to ensure they won’t come loose. Connect the manifold end back into the manifold, and replace the PCV Valve back into the valve cover. That is, unless you are a 3.8L owner, which you have a little more work to do.

    For 3.8L owners, take the hose on either end of the filter and use a zip tie to secure the filter to the wiring harnesses on the firewall. This will prevent the filter from flopping around. After you secure the new fuel hose to the wiring garness, go back and make sure the the PCV Valve and the manifold connections are secure.


    Cut two four and a half-inch (4 ½”) pieces of new fuel line to be attached to the new fuel filter. The left over three inches of hose from the one-foot section of fuel hose will be cut again later. Attach the four and a half-inch pieces of hose to both sides of the fuel filter and use two clamps to secure them. Use motor oil to help in seating the hoses firmly.

    Lay the fuel filter/hose assembly next to the metal hose assembly for preparation to cutting the metal hose. See below:

    Now, bend the hose ends down to the metal hose and leave at least a 1/2" overlap for connection of the clamps to hold the hose in place onto the metal hose. Note, in the above picture, those hose ends are NOT four inches long (I messed up!).

    Mark the spot where the hose ends will bend down to, and then cut the metal hose ½” longer than that mark. Extend your marks ½” toward where the fuel filter will be inserted into the line. Use either a pipe cutter (preferred), or a hacksaw.

    If you use a hacksaw, you MUST REMOVE ANY AND ALL FILINGS FROM THE LINE!!! After you cut the metal line, use a file to smooth it out a little. A small Philips screwdriver can be used to help round out the metal hose again if it was collapsed. Use brake cleaner, pipe cleaners or even string to help remove any debris in the metal hose. Blowing into one end of the hose until you see spots will help too! Connect the ends of the fuel hose to the ends of the metal hose and use the remaining two clamp to secure them. Remember to use a little motor oil to aid in seating the hose ends properly.

    This is how it should look when you are done:

    You’re almost done with the fabrication now. If your old rubber hoses were pretty rotten, you can take the remaining three inches of hose and replace the manifold end and the PCV Valve end with it. Cut the remaining piece of fuel line into a one inch and two inch piece. Put the two-inch piece of hose onto the end of the metal hose that goes into the manifold. This will give you some flexibility when positioning the fuel filter. Put the one-inch piece of hose onto the end where the PCV Valve will be attached. No clamps are needed, and besides, you don’t have any more!

    Now use your zip ties to secure the fuel filter to the wiring harnesses behind it. Zip tie locations should be a few inches away from the ends of the filter so as to allow you to unscrew one end of the filter for changing out the filter in the fuel filter housing, noted by the yellow arrows in the last picture below:

    Recheck that all of your connections are secure. This is a metered system and you don’t want any leaks even though the pressure running through this system is very small!

    Make sure that you check the fuel filter every time you change you Mustang’s oil and inspect it for excessive oil build up or puddeling. The pic below shows my almost finished project, I didn’t have any zip ties and used a clamp instead. I hope this article was helpful, and if anyone has anything to add, please feel free to do so. Enjoy!

    Moderators, if you want to make this a sticky, please do, but I stuck all the pictures in the Testing area. If you would like a MS Word 2000 version of this, let me know, and I will send it to you.
  3. i just put a breather on mine cus here in virginia, we are not ruled by environmentalist nut jobs, yet....