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Building a PCV System Breather Vent

by Russell Knize; reprinted by permission

This page describes how to build a PCV breather oil canister. Its purpose is to sit between the PCV breather vent hose and the air box. It will catch the oil leaking out of the vent, while recirculating the gasses back into the engine as before. Modifying your PCV system may or may not be legal in some states.

The Problem

From mid-1987 through a date in the 1990s, Chrysler decided that it wasn't necessary to properly install the crankcase breather baffle on the valve cover. This baffle was designed to allow crankcase gasses to escape while keeping the oil inside by running the gasses through a series of channels. Since the channels are not sealed against the valve cover properly, the oil bypasses them and exits out
the breather vent into the PCV system. The net result is oil in your airbox.

You can either try to fix the baffle, or you can build one of these oil canisters to catch the oil before it gets to the filter.

What You Will Need

To build a canister, you will need the following parts. They are available at your local home improvement centers and auto parts stores.

  • Schedule 40 PVC 2" female pipe to female threaded pipe adaptor
  • Schedule 40 PVC 2" female pipe to male threaded pipe adaptor
  • Schedule 40 PVC 2" female pipe cap
  • Schedule 40 PVC 2" pipe (length depends on the application)
  • CPVC 1/2" 45 degree elbow
  • CPVC 1/2" I.D. pipe (about 6 inches)
  • Copper 1" fitting to 3/4" pipe reducer
  • Crankcase breather for a Dodge Ram truck:
    • AC Delco FB101
    • Fram BA3632
    • Fram CA3632
    • Motorcraft FA-983
    • Purolator B43132
    • Wix 42997
  • PVC cement
  • Some sheet metal screws

To install the canister, you will also need the following parts:

  • 5/8" heater hose (length depends on application)
  • Hose clamps for 5/8" heater hose
  • New PCV breather filter (optional):
    • Fram BA7347 or CA7347 (early Turbo I)
    • Purolator B23157 (early Turbo I)
    • Fram BA6660 or CA6660 (other turbos)
    • Purolator B13162 (other turbos)

Putting It Together

You can assemble the PCV female-pipe to female-threaded adapter to the pipe cap either by cementing them directly together, or by using a short piece of 2" PVC pipe to cement them. If you decide to just cement them together, I recommend using a lathe to cut notches into the mating surfaces so that they can get a better grip. If you don't machine them, then at least sand the surfaces before cementing. Be sure you cement the right adaptor to the pipe cap. The notches you'd need to make are shown in the two bottom pieces in the picture below:


For the third PCV part (the female pipe to male threaded pipe adapter), you will need to make a notch anyway. This is to fit the PCV breather filter can into the adapter. If you don't have access to a lather, you could notch it out with a dremel, or melt the area by heating something that is the same diameter as the outside of the breather. I don't recommend heating the breather itself, because you will probably melt the filter inside, unless you buy two of them.

The next step is to put the copper fitting reducer onto the breather canister. Be sure to buy the right part. This is not a 1" pipe to 3/4" pipe adapter. It is a 1" fitting to 3/4" pipe adapter. The difference is that the larger end on the fitting adpater is smaller than on the pipe adapter. This is because the fitting adapter's large end is the same diameter as a 1" pipe, whereas the pipe adapter's large end is designed to accept a 1" pipe. Once you have the right part, you will see that it is slightly too small to fit over the lip on the bottom hose connection of the breather. You can either press it on by clamping the adapter and breather in a vise and pressing it in, or you can cut the lip off with a pipe cutter or hack saw and RTV it in place. I pressed it on and used RTV to seal it in place. The whole reason for the pipe adapter is to ensure that any dripping oil drips down into the bottom of the canister and not over to the vent.

Speaking of the vent, it is time to put it into the female pipe to male threaded pipe adapter. Do this by drill a 5/8" hole in the side of it. The hole needs to be above the threaded area, but low enough to clear the canister. If you adaptor is way too short to do this, then you got a CPVC adaptor and not a Schedule 40 PVC adaptor. Be sure to get the Schedule 40 version!


Once you have the hole drilled, you can glue a short piece of 1/2" CPVC pipe into the hole. If you are going to cement a fitting right to it, a 3/4" piece is about right. You can also use about a 1 1/2" piece and have the exit point straight out. Since 1/2" CPVC pipe has a 5/8" outer diameter, it is perfect for 5/8" radiator or emissions hose. Or you can glue a 1/2" CPVC "street tee" fitting right into the hole if you have a tight spot. What you do with the vent depends on the amount of clearance you have and the direction that you want the exit to point. For my application, I cemented a 3/4" piece of 1/2" CPVC pipe into the hole for a 1/2" 45 degree elbow that will be cemented to it. The image to the left shows to two sections glued together. The vent pipe is pointing towards the right, rear.

The last thing to do it to mount the filter breather to the top section. Drill 3 or 4 small 1/8" holes through the PVC adapter and the lip of the breather. Apply RTV around the lip for a good seal and use 1/4" #6 sheet metal screws to hold the breather in place.

Below: the parts; using the RTV; the finished product.


The final installation of the canister depends on your situation. A 2 1/2" muffler hanger works well for 2" PVC pipe fittings, and they are flexible. The stock PCV breather vent pipe on the engine is a good place to start when trying to figure out where to put the canister. You can cut the pipe so that it works better for you. The hose from the pipe to canister should be made of emissions hose, because rubber radiator hose breaks down over time, when exposed to engine oil. Though it can be tricky to find, emissions hose can be found in 19/32" ID, which is just slightly smaller than 5/8" radiator hose. If the canister is put together properly, no oil should escape the vent and regular 5/8" radiator hose can be used here.

If you intend to connect the canister vent back to the induction system somehow, the canister should be connected as intended. That is, the metal hose connection on top should be connected to the PCV breather pipe on the engine, while the PVC side connection should be the vent back to the induction system. If you are connecting the vent back to a stock airbox, make sure you install the correct breather filter for your airbox. This will help keep debris and condensation out of the canister.

The following is illegal in most states: If you are going to allow the canister to vent to the atmosphere, you have the option of connection the canister in the opposite way. This way, the gasses are vented through the top connection, and are filtered to prevent debris and condensation from entering the canister. [Allpar does not recommend letting the canister vent to the atmosphere].

Last updated 4/3/01. Questions - contact rknize [at]

Feedback and additions

Dave Brooks wrote:

I installed Russell Knize' breather filter on my 2.2L Shadow and it works great! More oil comes out of the engine than I previously believed. It can be good to install a compressor air tank style stopcock into the bottom of the breather canister to drain oil that pukes out of the valve cover. Or, better yet, perhaps mount the canister high enough to allow flow-back ito the valve cover or construct a tee or thread-in into the valve cover to allow oil to go back where it belongs.
Alan Bishop wrote:

My '87 Daytona Shelby had belched oil all over my brand new K&N filter. I was prepared to build Russell's filter, until I realized the problem is simply the valve cover itself. I went to a local boneyard and found an '86 Lancer turbo, with a nice shiny valve cover just waiting for me. $16.39 later, the problem was solved.

Russell has an inspired idea, and I'm not putting him down. I guess I'm kind of bragging about my good luck. Between Allpar, my Haines manual, and "U-Pull-Apart" in Milan, IL, I can virtually side-step the dealership. The best example were my three broken power window plastic tracks; broken at three different times, I paid $5 for the first one, and got a, "Have a nice day" on the other two occasions, when the employees didn't know what to charge. Would the dealership (or any mechanic do that)? Not for $5. The only trick to the yard is not to get depressed if something you need isn't there. The inventory revolves on a weekly-to-monthly basis, so "new" cars are coming in all the time.
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