Pre-Flight - Drain Gascolator

[Skates97]

The POH is fairly lacking in detail as far as a pre-flight inspection goes. It says to drain the sumps on each tank but does not mention pulling the ring by the fuel selector to drain the gascolator (I think that is what you call it). From other checklists that I have seen, that step is included so I have included it on mine, pulling the ring for 5 seconds, switching to the other tank and pulling the ring another 5 seconds. One of the last steps on my checklist is to make sure that it has stopped draining.

Last week I went out to fuel up and do some night pattern work. When I got back and put her back in the hangar I went about all the little things before heading home and noticed a tiny wet spot on the floor under where the gascolator drain is. I took a closer look and it had a very slow drip, took about 2-3 minutes for the drip to form and fall. I didn't notice before flying because the floor was already wet from draining it and the drip was so slow. Pulled the ring a few times and that fixed it, must have just not completely sealed before. I don't think it would have been an issue as it would have taken hours for even a cup of fuel to drain, but still is not something I was excited to see.

My question is, what purpose does it serve to drain it and just run the fuel on the floor? I can't see it to see if there is any water/sediment in it. I can't even see it draining, I just listen for it hitting the floor and then I can obviously see the wet spot on the floor when I climb out. It isn't listed as a pre-flight step in the POH (but then there are a lot of things that aren't listed that should be checked). I sump the wing tanks to make sure they are clear so I would imagine that if the fuel coming from the tanks is clear then the fuel there at the gascolator should be clear as well. Is this a necessary safety check that needs to be performed, or am I just dumping some avgas on the hangar floor for no reason?

[mooniac15u]

I had a slow leak like that from the gascolator in my old M20D.  It leaked a lot faster with the fuel pump running.  Please be careful.

On some of them you can also drain it from the outside.

[Andy95W]

Richard- I rarely pull mine, but every now and then is probably a good idea- until the plunger develops a leak and you wish you hadn't bothered.

There is a way you can check for water by yourself, though- drain a little on the concrete floor and then go and take a look at it.  The avgas will evaporate very quickly, if there is any moisture left after the gas evaporates, it must be water.

[N201MKTurbo]

You can drain it from outside with your fuel sampler.

[Guitarmaster]

I stopped pulling the ring because I couldn't, or didn't want to get back out to check if it was still coming out.

Now I use my sump cup and insert it into the drain.  This way I can see any water just like the wing and I know it has stopped draining.

[carusoam]

1) draining fuel on the hangar floor.  Nobody is going to appreciate... do this outside.

2) changing the tanks to drain both lines is a good idea...

3) draining using a fuel cup from the outside adds some value.  Inspect for dirt and water...

4) finding the drain doesn't stop while outside is a bit of a surprise.  Slow methodical return to the cabin....

5) losing a drip of fuel every minute or two is not the same problem as having air bubbles entering into the fuel system.  The cause is the same but the effect is a bit different...  stop the drip so you don't have air entering the fuel system...

 

Some ideas that come to mind....

PP ideas, not a mechanic or CFI....

Best regards,

-a-

 

[Yetti]

I have an old quart mason jar and a custom cut piece of tubing that sits inside the mason jar which holds it up against the drain.   Get in pull ring, switch tanks, pull ring.   then inspect jar.  Then put fuel in tug.

 

[Skates97]

3 hours ago, carusoam said:

5) losing a drip of fuel every minute or two is not the same problem as having air bubbles entering into the fuel system.  The cause is the same but the effect is a bit different...  stop the drip so you don't have air entering the fuel system...

I hadn't thought of that, thank you.

3 hours ago, Yetti said:

I have an old quart mason jar and a custom cut piece of tubing that sits inside the mason jar which holds it up against the drain.   Get in pull ring, switch tanks, pull ring.   then inspect jar.  Then put fuel in tug.

I like this idea, eliminates getting in and out to switch to the other tank if I were to just use the sampler from outside.

However, is it really necessary to drain it as part of the pre-flight? Like I said, it doesn't say to in the POH and it seems that some people do it and some people don't. In my mind I think that if the tanks are fine when I drain them then likewise the gascolator should be fine as well and not need to be drained, but what makes sense in my mind doesn't always line up with reality...

[ArtVandelay]

Isn't there a fuel filter/screen in the gasolator?

[Yooper Rocketman]

I apply some common sense to draining mine.  I rarely do it as I almost never find water in my wing tank drains and in 21 years of Mooney ownership have never had water in the gascolator sump of either of my Mooney's.  If I ever find moisture in the wing tanks, then I drain the gascolator.  If it's been quite a while since I drained it, I will do it for good measure.  I also pull the unit apart during annuals and clean the screen. (Yes teejayevans, there's a screen in it).

Agree on the dumping on the floor issue.  I always place a clean pan underneath when I DO drain it so I can verify if there is any water or contaminants in it (again, I've never had anything in the gascolator in 21 years).

[TonyK]

I cannot speak to real world experience since I haven't taken delivery of my M20F yet but I do have a POH for it.  It does have it listed in the Preflight.

[Raptor05121]

My M20D does not have the pull-ring, but rather have to get on your back and reach into the very forward of the nosewheel well. I did this once when I took delivery. The previous owner laughed, said he's done it once when he bought it as well, and never bothered again. I have heeded his advice. I fly 2-4x a week. My wings tanks always sump clean, I have no worry.

[triple8s]

My CFI told me of a mooney driver who ran out of fuel and crashed. He took off with plenty of fuel, slumped the tanks, pulled the gascolator and evidently one thing or the other didn't stop leaking and he lost his fuel. Since I heard this the first thing I do is to sump both, pull the gascolator then push the plane back a few feet. Next I do the exterior preflight and before I get in the plane I look at the ground under the plane if something is leakin it is easy to see.

[carusoam]

Richard,

Make sure you have two versions of the POH...

The 1965 version is good for legality reasons.

The 1976 version has all the details that were left out in the early years.

If you park outside, expect water to be in the tanks, until you verify that the fuel necks have been updated to stainless steel and both of the o-rings in each cap have been proven to be working.  There is a better material for these things that isn't original...

Flying a plane in 1965 must have been an interesting experience....  membership in a Mooney club must have been a requirement to stay alive...

the screen at the bottom of the ’65 and newer planes is there to make sure the dirt and rust is small enough to get stuck further down stream...  

older than 65 has the glass gascolater in a different place...

Stainless parts and new rubber o-rings should keep rust bits from forming.  Newer tank sealant material will keep rubber bits from stuffing off and moving for the exits.... living indoors is pretty good for the rest of the details...

mine lives indoors and still gets sumped and drained.  A small speck of dirt will show up every now and then....  probably the remnants of a bug trying to clog my fuel vents...

Best regards,

-a-

Edited February 22, 2017 by carusoam

[DonMuncy]

10 hours ago, Skates97 said:

My question is, what purpose does it serve to drain it and just run the fuel on the floor? I can't see it to see if there is any water/sediment in it. I can't even see it draining, I just listen for it hitting the floor and then I can obviously see the wet spot on the floor when I climb out. It isn't listed as a pre-flight step in the POH (but then there are a lot of things that aren't listed that should be checked). I sump the wing tanks to make sure they are clear so I would imagine that if the fuel coming from the tanks is clear then the fuel there at the gascolator should be clear as well. Is this a necessary safety check that needs to be performed, or am I just dumping some avgas on the hangar floor for no reason?

I have an oil drain container, about 4 inches deep to place under the gascolator. As you describe, pull the ring for 5 seconds, switch tanks, pull for 5 seconds. Then, examine the oil drain pan for water.

[Skates97]

Thanks again for all the feedback. I will look for the 1976 version of the POH. I see a 1970 version in the download section. Does anyone have a digital copy of the 1976 POH? If not I'll do some searching tomorrow. 

[MB65E]

My pull ring and plunger assembly is removed. I have a 1/8in Curtis 1550 drain valve. Super simple. Easily replaced whenever needed. 

I sump it every flight usually alternating wing tanks. 

I always thought dumping fuel the way it was designed was strange.

-Matt

[mooniac15u]

13 hours ago, Raptor05121 said:

My M20D does not have the pull-ring, but rather have to get on your back and reach into the very forward of the nosewheel well. I did this once when I took delivery. The previous owner laughed, said he's done it once when he bought it as well, and never bothered again. I have heeded his advice. I fly 2-4x a week. My wings tanks always sump clean, I have no worry.

That previous owner gave you bad advice.  Water in your fuel system can ruin your day.  The gascolator is your last line of defense.  It is easy to become complacent when you don't normally find anything but it only takes once.  The gascolators in the early models are in an inconvenient location but they also have glass bowls so it isn't hard to see if there is water or other contaminants collecting inside.  You should be looking up in your landing gear bay anyway to check for condition of your gear and any foreign objects like birds nests.  Use that opportunity to look at the gascolator.

[mooniac15u]

19 hours ago, Skates97 said:

My question is, what purpose does it serve to drain it and just run the fuel on the floor? I can't see it to see if there is any water/sediment in it. I can't even see it draining, I just listen for it hitting the floor and then I can obviously see the wet spot on the floor when I climb out. It isn't listed as a pre-flight step in the POH (but then there are a lot of things that aren't listed that should be checked). I sump the wing tanks to make sure they are clear so I would imagine that if the fuel coming from the tanks is clear then the fuel there at the gascolator should be clear as well. Is this a necessary safety check that needs to be performed, or am I just dumping some avgas on the hangar floor for no reason?

Draining the gascolator will remove water and debris even if you don't see it happen.  It would be better to look at what you have drained but there is value in draining it even if you don't see it.

[Yetti]

So for my Landing gear actuator I found information on a tractor forum.   Is this the same glass bowl the older Cs have?   Like off a Ford 8N tractor?

https://www.amazon.com/Tisco-2NAA9155B-Sediment-Bowl-Assembly/dp/B00CYZFQOE

[carusoam]

Check to see what keeps the bowl from vibrating its retainer nut loose?

The aviation one might have a safety wire hole through it?

PP Thinking out loud only, not a mechanic...

Best regards,

-a-

[Yetti]

You mean like needed one of these. https://www.amazon.com/BikeMaster-Drill-Guide-Safety-Accessories/dp/B003177UIO/ref=sr_1_2?s=industrial&ie=UTF8&qid=1487772239&sr=1-2&keywords=safety+wire+drill+jig

 

And I am concerned that Amazon knows what kind of motorcycle I have...

And no I am not suggesting using non PMA parts on a certified plane.   I just think it is interesting to know the lineage of the parts that can take us far above the safety of the ground.

 

 

[mooniac15u]

12 minutes ago, Yetti said:

So for my Landing gear actuator I found information on a tractor forum.   Is this the same glass bowl the older Cs have?   Like off a Ford 8N tractor?

https://www.amazon.com/Tisco-2NAA9155B-Sediment-Bowl-Assembly/dp/B00CYZFQOE

On my 1963 D it was bigger than that and had a drain valve.  It looked a lot like this metal one but the bowl was glass:

http://www.aircraftspruce.com/pages/ep/gascolators/acsgascolator.php

[Bob - S50]

I drain my gascolator on the first flight of the day every time.

1.  I sump the tanks first.  If there happened to be water in the tanks and I did the gascolator first, I would introduce water into the line between the tank and the gascolator.

2.  Pull the gascolator ring for 5 seconds on each tank.  While I suspect there is rarely anything there, it is worth it to me to waste a 1/2 cup of fuel to get rid of any water or dirt that might be there.

3.  Do the walk around and make sure it isn't leaking.

I'm starting to like triple8s idea of moving the plane before I do my walk around.  Or I suppose I could just make sure the puddle evaporates before I leave.  One time I found an extra puddle under the plane.  The left wing sump drain had not completely seated and developed a slow drip.  Had to sump it several more times to get it to seat.  Must have been a small piece of dirt in there that I couldn't see.

[mike_elliott]

21 hours ago, N201MKTurbo said:

You can drain it from outside with your fuel sampler.

I personally would not recommend doing this, as it can potentially damage the plunger that seats causing a slight leak. A better practice is to pull the gascolator ring for each tank when you begin the preflight with doing the interior work as noted in the poh first., then doing the exterior tasks. You will know if it is still running out. As another poster said, it is better to sump the wings prior to pulling the gascolator ring, however.

The purpose of pulling the gascolator ring is to remove any sediment that may be accumulating prior to it plugging up you carb jets or finger screen in the servo, like what was happening in another thread here recently that the op is now trying to sell the plane because of. Yes, there is a screen in the vintage gascolators that should be checked at each annual, along with the finger strainer screen in the injected IO360's, but they don't catch everything.