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No Two Alike
My Lycoming engine originally came with an oil screen, and later was fitted with a canister type oil filter, but your Cherokee may be different from mine. The fact is that there are no Piper Cherokees exactly alike due to ADs, STCs and a procedure called an Engineering Order (EO).
As a student working for Piper in Vero Beach, I remember an English supervisor explaining to me that the Piper Cherokee models didn’t really change year by year as much as they changed by Engineering “Oww-daas.” This meant that when a change was approved, it was immediately added to the production line process and the improvement was installed in the very next airplane.
So Rule No. 1 is that no Pipers are exactly the same, and Rule No. 2 is if the photos in this article show you something that’s not the same on your airplane, don’t panic.
Drips at the dipstick and drain
The dipstick can often be the first point to drip, because it has quite a bit of oil on it when you pull it all the way out. After warming the engine (either by flying the plane or by preheating), the best practice is to have a shop towel ready when you pull the dipstick out of the engine, then to wipe it off and put it in a clean place until the oil change is complete.
If you’re lucky, you have a spring-loaded, quick-drain oil sump valve at the bottom of the engine. The sump has a small T-handle that pulls up, turns and locks into place, allowing the oil to drain freely from the engine.
Of course it’s important to close the sump by turning the handle to close the valve before adding the new oil. It’s also worthy of mention that the sump valve is made of brass and if it is allowed to snap back into place, it could cause the valve inside to warp and start dripping. So operate the sump handle smoothly.
The author’s technique
The procedure to drain the old oil from your engine would be to open the oil sump valve and drain the oil into a five-gallon plastic bucket. To do this, I recommend that you visit the hardware store and buy a piece of ¾-inch (OD) PVC about two or three feet long, a piece of ¾-inch (ID) plastic tubing about 12 inches long, one hose clamp, a small bungee cord and a five-gallon bucket.
The reader probably wants to ask, “Why don’t you just buy three or four feet of plastic tubing?” The reader might also ask, “Why a five-gallon bucket?”
Well, I came up with this combination due to trial and error. It seems that plastic tubing comes on a reel and seems to have a memory where it always wants to stay curled up. Eventually, it will get away from you—by pulling out of the oil bucket, or some other way—dripping oil all over.
Consequently, I use 12 inches of tubing for an elbow, and the PVC as a more controllable direct route to the oil bucket. The PVC should be cut so that it only goes halfway into the bucket. Use a tiny bungee to hold the top of the tube securely to the sump by stretching it from the clamp to the engine support. I find the five-gallon bucket is taller than oil receptacles sold at auto parts stores and will provide more leverage to keep the PVC tube in the bucket.
When the oil has been drained from the engine, carefully disconnect the tubing and wipe the sump off with a shop towel, and s-l-o-w-l-y close the oil sump valve. Insert a piece of shop towel into the plastic tubing to prevent any oil drips from the top end, and carefully remove the tubing from the engine compartment without removing the lower end of the tube from the bucket of oil. Hold the tubing in the bucket, and move the bucket to a safe area where the tubing can be removed and laid on newspaper or cardboard.
Drips at the filter and recovery container
The filter is the next drip point, and probably the worst. Clip the safety wire off the filter to prepare to rotate the canister filter counterclockwise.
Will the oil filter be drained by loosening it a couple turns and letting the excess drip out, or by poking a hole in the top, rotating the filter 180 degrees and making an air hole to let oil drain out of the hole on the bottom of the canister? Make sure you’ve decided ahead of time which technique you’ll be using, so you are prepared. Additionally, the oil that comes out must be recovered in some kind of small container.
The best oil recovery tool for catching the oil from the oil canister is an empty plastic oil or milk container. Generally, it’s best to start by trimming a plastic oil can with a box cutter, so that when it’s placed under the oil filter, the oil can drip into the oil can. The same thing can be done with a milk jug.
Place a rolled-up shop towel under the oil canister and against the engine to catch the inevitable couple of drips when the canister is loosened. Everyone knows this trick, but the devil is in the details—and by that, I am talking about the oil drips generated when removing the plastic container from the engine compartment.
If the plastic oil container is full to the top after draining the oil from the filter canister, some of the oil will probably spill as you attempt to turn yourself into a pretzel removing it from the engine compartment. The larger the container the better, but not too big as it will have to travel through the maze of wire and engine support tubing when removed from the engine compartment.
Using a clean shop towel, clean the area of the engine block that the oil filter forms a seal on, place some clean oil on the rubber seal of the new oil filter and install the new oil filter canister using a torque wrench. Replace the safety wiring.
Double-check the following before adding the new oil: the oil sump valve is closed; the new oil filter has been installed; the new oil filter has been safety wired.
After the check, it’s then time to add the new oil. Remember the dipstick? Well that’s where the new oil will be put into the engine and it can be another source of oil drips. It’s a pretty small opening and there are paper funnels that you can use, but from my experience, it’s patience that keeps that oil from dripping.
It’s a good idea to wrap a shop towel around the mouth of the intake in case your hand slips. Open each plastic container of oil and s-l-o-w-l-y add each quart. When finished, wipe the mouth of the intake with a clean shop towel and replace the dipstick.
You’re not done yet; don’t let guard down. Review everything you have done: Oil sump valve closed; new oil filter canister installed; safety wire installed; new oil added; and dipstick replaced.
Now… remember that safe place that we put the oil bucket, the old oil filter and the empty containers of oil? Loose items need to be put into a trash bag or separated for recycling, and the tubing needs to be wiped off with a shop towel and plugged at both ends with a piece of shop towel. The oil bucket will need to be taken to a place that accepts old oil. No oils should be allowed to touch the ground.
The moment of truth
Now you’re ready to test your work by running the engine. While the engine is running, make sure the oil pressure is in the green. After running, look in the engine compartment for oil leaks, either caused by a mistake or an act of God (the rubber gasket in the oil filter would drip oil if it got folded when the filter was installed, for example).
And lastly, don’t forget the endorsement in the logbook: name, certificate number, date, place, what was done, and that the airplane was tested and returned to service.
Most pilots know how to change their oil, but hopefully this article sheds some light on how best to do so and remain “dripless.” Happy flying!