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Oil Catch Pan for Oil Filter

PhatRV

Well Known Member
I found this nifty oil catch device from the SX300 forum. It should catch all the oil dripping as the oil filter is removed and drains the oil overboard. This will work for the nose wheel models but the tail wheel models need some adjustment.
 

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I bought one of these compact oil filter drain funnels designed specifically for aircraft filters from fellow VAF'r Steve Melton (rvplasticparts.com) and couldn't be happier. Everybody in the shop is always looking to use it. Our Form-A-Funnel hardly gets used now.


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My accessory case is my catch pan. The very first step I do for an oil change is that I take a drift punch and put a hole in the top of the oil filter. Then I set up to drain the oil sump, take my oil sample, undo the safety wire on the filter, and go get a soda. I come back a half hour later and the sump is empty, and so is the filter. all the oil in the filter has drained out. I unscrew the filter and put a rag under it, and honest, I spill maybe one drop of oil out of the filter.

I guess this is predicated on having the 90-degree filter mount. If the filter is horizontal, I guess the best you can do is drain half.
 
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Interesting discussion. With a vertical oil filter (90 degree adapter with filter mating surface on the bottom) wouldn't the filter drain down on its own overnight after shutdown? Or is there a built-in check valve or vacuum lock that keeps this from happening? I know the 108/109 filters have an internal bypass valve and the 110 filters do not so could this be a factor in a awl vent hole punch facilitating internal draining of the filter? I used to partner in a Pitts with a 90 degree adapter and it always seemed full of oil and ready to coat the back side of the engine, mount and hangar floor.

If punching a hole in the filter causes filtered debris to return to the sump or oil pump does it come from the outer filter media pleat side or from the center hole of the filter? Looking at this fine diagram from Dan H it appears that the oil pump side oil (pressure) enters the filter through the small circumferential holes around the periphery of the filter and then returns filtered oil to the engine galleries for lubrication via the large threaded center hole:

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So what happens when a hole is punched in the top domed area of oil vertical filter to aid draining the filter? Does the oil drain out the center of the filter (filtered) or back around the perimeter pressure side towards the oil cooler/oil pump (unfiltered)? Both? Regardless of scenario do the paper pleats tend to keep a hold on to shavings/dirt by their geometry of folded triangle cross section forming tapered wedges holding the stuff in place? And finally on a properly broke in and maintained engine does any filter backflow make a noticeable difference in engine life? Lycoming list the same TBO without an oil filter using a rock-sized screen as it does with an oil filter trapping fine particuate. I am not advocating either way but personally would err on the conservative belts and suspenders side of using an oil filter and not draining it back internally until some of these questions are answered. Understanding is a huge benefit in aviation.
 
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When my A&P was showing me how to change my oil, he used a Form-a-Funnel for managing the oil filter. I was impressed and promptly bought one for both the hangar and my garage at home.
 
Before I loosen the filter, I place my funnel / drain hose under the base, punch a hole at 12 o'clock near the base, loosen 180*, punch a vent hole at whats now the top. Filter drains pretty quickly from the first hole which is now at 6 o'clock.

I have a Casper 45* adapter, but this method should work on a horizontal filter as well.
 
Rotax filter tray

This plastic tray works well with the Rotax 912 oil filter that is mounted horizontally. The process is to loosen the filter so it can be turned by hand, then hold the tray under the filter while it is fully removed. The oil dribbles into the tray, and when the filter comes off it also goes into the tray. There is very little if any mess.
 

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Doing this will cause shavings and whatever loose junk is in the filter to work their way back down into the oil pump.

The VAST majority of the drain-back oil is from inside the filter element, so it has already been filtered. The small volume of oil around the outside of the filter element drains back through one small hole. Extremely unlikely that any chunks would find their way back out that hole -- they would stay in the filter. fine shavings are trapped on the paper element.

Tell you what, next oil change, I will not drain it back, and when I open it up, I can compare the metal content to my normal baseline. I'll report back if there is any difference.
 
Tell you what, next oil change, I will not drain it back, and when I open it up, I can compare the metal content to my normal baseline. I'll report back if there is any difference.

Often I find crud outside of the filter and laying inside the can. Last year I did 24 annuals on certificated aircraft so I check filters 30-40 times a year. If you study an accessory case the inlet to the filter is thru the passage directly from the oil pump (edit: when cold. This is to prevent cold congealed cold oil from blowing up the oil cooler.) Draining oil by venting the filter goes right back into the oil pump gears where said junk could get lodged and cause scoring in the pump housing. Its not valid to take your potentially clean engine oil and filter and say see nothing is wrong with this practice. Its your airplane and you can certainly do as you please but I don't advise people to punch an air hole in a filter so it leaks down.
 
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The VAST majority of the drain-back oil is from inside the filter element, so it has already been filtered.

Also, this statement is incorrect. Oil is fed from the oil pump to the outside of the filter. The path of filtered oil, which is the center of the filter, does not drain back. Unless oil can go uphill to the oil pressure bypass.
 
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Aren’t you guys saying the same thing?

No. Oil is fed to the outside of the pleats from either of two paths. Thru the center of the filter is where filtered oil exits the filter and feeds the engine. Filtered oil cannot drain back to the sump thru that circuit.

I just looked at a filter body and accessory case. I am correct in that unfiltered oil can be returned from the oil pump two ways: 1, from the oil cooler and 2. from the oil cooler bypass if the vernatherm is open (cold.)

Learned something here though...if the oil is hot (vernatherm closed) then there is no path for oil to drain thru the filter body, but it would eventually, as the vernatherm opens. Unless it went uphill thru the center of the filter and from there on to the oil pressure bypass.
 
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One thing I am reminded of today and that is that its probably a good idea to put a tee fitting at the bottom of the oil cooler as does Cessna in later model 172s. From there you can drain the oil cooler, and potentially drain out any junk in the cooler while oil is hot.

I have seen a few occasions where engines were overhauled due to making metal and the oil cooler not replaced, which resulted in damage to freshly overhauled engines.
 
The path of filtered oil, which is the center of the filter, does not drain back. Unless oil can go uphill to the oil pressure bypass.

I don't understand why you say this. My filter sits up almost vertical, with the mounting face at the bottom. It is not uphill to anything for the oil in the center area of the filter to drain down thru the center fitting.
 
One thing I am reminded of today and that is that its probably a good idea to put a tee fitting at the bottom of the oil cooler as does Cessna in later model 172s. From there you can drain the oil cooler, and potentially drain out any junk in the cooler while oil is hot.

I have seen a few occasions where engines were overhauled due to making metal and the oil cooler not replaced, which resulted in damage to freshly overhauled engines.

Yes, I have occasionally wondered about that. Maybe not every oil change, but once in a while, it would seem like a good idea to drain the cooler.
 
Its not valid to take your potentially clean engine oil and filter and say see nothing is wrong with this practice.

I don't understand this. I am talking about next time I change my oil (dirty oil) I will pull the filter without draining it and see if the level of metal is different. I typically get a little pile of fine chips that would form a sphere about 0.15" diameter out of my filters. If my normal practice is allowing some chips to drain back into the engine, then I should find more metal when I pull it without draining. I don't see a flaw in that logic.
 
I don't understand why you say this. My filter sits up almost vertical, with the mounting face at the bottom. It is not uphill to anything for the oil in the center area of the filter to drain down thru the center fitting.

Perhaps then please explain to the audience here how filtered oil drains thru the threaded fitting (the center) back into the sump.
 
Perhaps then please explain to the audience here how filtered oil drains thru the threaded fitting (the center) back into the sump.

The threaded fitting is not very long - it only goes a short distance up into the filter before it meets up with the perforated tube that runs to the end of the filter, right? So you are correct, oil in the center area can only drain until it gets to the height of the threaded nipple. But that gets most of it. The rest may back-flow thru the filter paper back into the outer cavity and drain thru the opening for the pressure side. That could be a problem because in the process, that flow may wash anything partially bedded into the paper out and drain it back.

Bob, please don't misunderstand my tone or motives here. I value your advise and I am sure I am not the only one that has been punching filters to drain them ( I learned the trick from someone). I'm just trying to understand all the details of the process to see if it actually is a problem or not. So I want to understand the points you are making.

Interestingly enough, the written instructions that came with my Casper filter adapter specifically say to do the punch trick. So they don't seem to think it's an issue. Of course, it's not their motor either.
 
You can do this without spending money. Just take a 1 quart plastic oil bottle and carve one side out of it, making sort of a pan/shell, leave the cap on. The Shell ones have a shorter neck and may fit better. The back end then fits nicely under the filter mounting flange. Don't need a drain line, just more mess, just carefully lift the bottle out of there after the filter is drained and removed.
 
I’ve been reading these kind of threads for years, and every post has value - but just be aware that none of the ideas will work in every situation, mostly because of the variation in engine and accessory installations. Somethign as simple as how you run your spark plug wires will change your access to the oil filter mounting point. Other variations include; type of pil filter mount, how close the firewall is to the back of the engine, type of prop governor, how the prop governor cable is mounted, choice of oil filter (check valve or not), how your oil cooler lines are run, where the oil cooler is mounted, which accessory case you have (which determines where the oil cooler lines come out.....), engine mount design, etc, etc, etc....

I’ve got a Form-A-Funnel, cut out milk jugs, various disposable Tupperware-type containers, and custom drip tray. Nothing works in very situation, but all have their place in the “box of ideas”.

I have worked on wide open engines where I never spill a drop and tight installations, where the only thing you can do is stuff rags under the filter and catch as much oil there as you can while flipping the filter as quickly as possible to stop it dripping.

The bottom line is that when people post ideas, they are all good - they are all something to look at to see if they will work for you. But don’t be disappointed if they don’t - your installation may vary. Remember - there is a rumor that Lycoming once made two identical motors - but no one has ever proven the rumor to be true. When you add the variations of installation (remember, these are Experimental aircraft....), the chance that you’ll have to come up with your own variation on all these ideas is is high.

Meanwhile, it all makes me appreciate my little turbine engine - I suck the 300 CC of oil out with a syringe through the dipstick hole, and squirt another 300 CC in and the screen never has oil in it, so no mess there - and that’s that! :)

Paul
 
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FWIW, I use an empty 1gal milk jug with the bottom cut out of it. They are flexible enough to fit just about anywhere an oil filter is installed. You can even let the old oil filter just drop in to the jug and retrieve it later. The best part is just unscrew the "top" off when you want to drain the oil out of it. Cheap, easy, readily available and it works great. YMMV

:cool:
 
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