Rotting fuel connection worth a check

[Gone Flyin]

When next you are having your plane inspected... or if you have noting better to do and you want to do it yourself, I have another one for you.

This one involves that pain in the butt fuel overflow on the Cessna 150 and, I assume, on other models, as well. That's the one where your $6.00 aviation fuel drips out of on hot days or when you put way too much in the tanks. Yes, I know all about the mod to keep this from happening. Some day, some day.

Found the short section of hose that connects the fuel overflow line to the drain port was dry rotted in my plane. Two hose clamps secure it to the two metal tube sections. This might lead to fuel dripping inside the wing, so feel around up there and see if yours needs replacing.

It's a simple enough fix but a one handed operation working blind. There is an access port right near the drain fitting.

Suggestion: if the hose is dry rotted it will be stuck to the tubing pretty well. If you warm up the hose with a heat gun it will make the removal way easier.

Just another tip to help others out there. As plane owners, we need to be vigilant.

It's our butt up there.

 

[Clip4]

That wouldn’t bother me to much because it carries zero fuel pressure. The ones carrying fuel would be my first check, they carry 1/2 pound fuel pressure. Normally you start noticing a fuel smell in the cock pit on preflight because the connects are getting hard and start seeping small drops of fuel.

 

[Gone Flyin]

Yah, you're right. Having gasoline sloshing around the wing... maybe running down to the electrical connection for the indicator lights is no bid deal.

Frankly, I don't know why I even bother to post these tips.

 

[Lndwarrior]

Yep, this is why I quit posting on here a long time ago. This board didn't use to be this way 10 years ago. Now, no matter what you post, you will get negative or snarky comments from someone who has the urge to try and prove they are smarter than you.

 

[Dan Thomas]

That isn't an overflow. It's the tank vent, for both tanks, and it's critical. Cessna publishes positioning information behind the strut for that thing, to get the right amount of head pressure in the tanks.



There are also short pieces of rubber hose in the vent crossover between the tanks. They're miserable to get at. The tank covers have to come off and you might even have to get the headliner out to get at the clamps inside the ceiling. They rot, and I have had fuel running down the doorposts of an old Cessna because those things rot away.



These pics are from the '69-'76 150 manual. Check the manual that applies to your model year.

 

[BPM]

Yah, you're right. Having gasoline sloshing around the wing... maybe running down to the electrical connection for the indicator lights is no bid deal.

Frankly, I don't know why I even bother to post these tips.

Please don’t stop posting. Do your best to ignore the ungrateful responses (and responders). I for one greatly enjoy and benefit from the knowledge that you and others generously share on this forum.

Perhaps I, and others in similar position (primarily readers not posters) should be more vocal in our appreciation?

 

[Fearless Tower]

Yah, you're right. Having gasoline sloshing around the wing... maybe running down to the electrical connection for the indicator lights is no bid deal.

Frankly, I don't know why I even bother to post these tips.

You don’t have to act all butthurt about it.

Your observation is valid, Clip was just pointing out that checking/replacing pressurized/fuel carrying lines and hoses would be the priority.

 

[Matthew Rogers]

Yah, you're right. Having gasoline sloshing around the wing... maybe running down to the electrical connection for the indicator lights is no bid deal.

Frankly, I don't know why I even bother to post these tips.

To be fair, your tip does not even call the object by its correct term and function. As others pointed out it has nothing to do with fuel overflow, it is solely for venting and the only time you should have fuel coming out is if you completely top off the tanks up to the brim and then don’t take off immediately.

And you may also want to check out that fuel vent tube diagram as your vent tube does not seem to conform to the original requirements when looking at your picture. Yours seems to be closer to the A150 (you may have an aerobat), but still not parallel to the bottom of the wing.

 

[Magman]

It seems to me OP has called attention to a possible concern.

I did not get the impression he was posing as a Cessna Tech Rep so proper nomenclature is not essential.

ie The alarm “Fire!” is about the same as “ Rapid oxidation accompanied by Heat!”

Always helpful when folks point out issues and remedies as they know them.

 

[Dan Thomas]

Always helpful when folks point out issues and remedies as they know them.

As long as the advice is informed and correct. Thrre are non-mechanics telling people how to fix their airplanes. Youtube is a bad place for that. One can "fix" something and make it more dangerous.

 

[Salty]

It seems to me OP has called attention to a possible concern.

I did not get the impression he was posing as a Cessna Tech Rep so proper nomenclature is not essential.

ie The alarm “Fire!” is about the same as “ Rapid oxidation accompanied by Heat!”

Always helpful when folks point out issues and remedies as they know them.

Better check your muffler bearings quick before your plane blows up!

seriously though. There’s no fuel in that hose 99.9999% of the time, so not sure how critical this is.

 

[Matthew Rogers]

Better check your muffler bearings quick before your plane blows up!

seriously though. There’s no fuel in that hose 99.9999% of the time, so not sure how critical this is.

It is critical that it is open to allow air into the tank. I almost crashed (surging, partial power in a C150=going down) because of a blocked fuel vent line. But it is correct that fuel only enters the tube when both tanks are completely full up to the brim.

 

[Dan Thomas]

It is critical that it is open to allow air into the tank. I almost crashed (surging, partial power in a C150=going down) because of a blocked fuel vent line. But it is correct that fuel only enters the tube when both tanks are completely full up to the brim.

You can actually lose a good chunk of fuel if the airplane is parked on a slope with the left wing low. The fuel from the right flows through the system to the left tank and out the vent. If the vent check valve inside the tank is stuck open it will run out like crazy.

McFarlane sells a vent line with a high spot in it to discourage that.

There is an AD that mandates vented fuel caps for the Cessnas, to prevent power loss if the vent is blocked

 

[Dan Thomas]

BTW: Hoses don't "dry rot." Dry rot actually requires a bit of moisture---humidity will do---to feed the microbes or fungi that eat organic materials such as wood. Hoses are made of synthetic polymers that gradually lose their lighter elements (evaporation) so that they shrink, harden and crack. You smell those elements leaving a new hose. Or tire. Hoses inside the wings and cabin roof get hot under the summer sun and pretty much get cooked. Hoses in the engine compartment get cooked even faster because of higher temperatures. Plastic pitot-static tubing also gets brittle and cracks.

 

[Matthew Rogers]

You can actually lose a good chunk of fuel if the airplane is parked on a slope with the left wing low. The fuel from the right flows through the system to the left tank and out the vent. If the vent check valve inside the tank is stuck open it will run out like crazy.

McFarlane sells a vent line with a high spot in it to discourage that.

There is an AD that mandates vented fuel caps for the Cessnas, to prevent power loss if the vent is blocked

Well, a broken check valve is an issue that must be corrected.

Too bad Cessna didn’t think about the raised vent tube at the factory, not too many people will ever both to replace the stock one. However, it is actually nice to be able to see some fuel dripping out from time to time as that is a visual check that assures you have at least a partially open vent line. Fuel out-air in. After my emergency, I now gently blow into the vent line during pre-flight to ensure it is open.

The vented caps are not enough for the C150. I had just replaced the cap gaskets and visually and manually checked the caps just a week before my venting issue. The O-200 may not draw enough fuel to create a strong enough vacuum to pop open the vented caps, at least at cruise power. Or they don’t always pop open enough to allow for full fuel flow. My vent tube was completely blocked and I was only able to get enough fuel for a surging engine with 2 vented fuel caps. So don’t count on the vented caps to work without a hitch.

 

[Dan Thomas]

Well, a broken check valve is an issue that must be corrected.

Too bad Cessna didn’t think about the raised vent tube at the factory, not too many people will ever both to replace the stock one. However, it is actually nice to be able to see some fuel dripping out from time to time as that is a visual check that assures you have at least a partially open vent line. Fuel out-air in. After my emergency, I now gently blow into the vent line during pre-flight to ensure it is open.

The vented caps are not enough for the C150. I had just replaced the cap gaskets and visually and manually checked the caps just a week before my venting issue. The O-200 may not draw enough fuel to create a strong enough vacuum to pop open the vented caps, at least at cruise power. Or they don’t always pop open enough to allow for full fuel flow. My vent tube was completely blocked and I was only able to get enough fuel for a surging engine with 2 vented fuel caps. So don’t count on the vented caps to work without a hitch.

The check valve is designed to let air in rapidly but out slowly. It has a flapper that has a tiny hole in it. The flapper is what you feel popping open when you blow into the vent. You should hear air escaping slowly right after that. Got to listen closely. The flapper gets gunk from fuel residue on its hinge and it can stick open. The orientation of the valve in the tank is also supposed to have the hinge at the top.

The vented caps must be oriented properly, too, with their handle fore and aft. Old airplanes had screw-in fuel filler necks that sometimes got turned a bit and then seized there. It puts airflow against the two small static vent ports in the cap handle and messes up the tank pressures. Those ports are important to avoid the low pressure over the wing from holding the fuel back.

 

[Matthew Rogers]

The check valve is designed to let air in rapidly but out slowly. It has a flapper that has a tiny hole in it. The flapper is what you feel popping open when you blow into the vent. You should hear air escaping slowly right after that. Got to listen closely. The flapper gets gunk from fuel residue on its hinge and it can stick open. The orientation of the valve in the tank is also supposed to have the hinge at the top.

The vented caps must be oriented properly, too, with their handle fore and aft. Old airplanes had screw-in fuel filler necks that sometimes got turned a bit and then seized there. It puts airflow against the two small static vent ports in the cap handle and messes up the tank pressures. Those ports are important to avoid the low pressure over the wing from holding the fuel back.

That is an interesting fact. One of my caps is aligned fore-aft, the other is clocked differently. So at least one should have worked correctly. My fuel tanks have a 6 (or 8?) bolt hole pattern fuel filler neck. One of those must have been improperly indexed when installed as that determines which way the cap sits when tightened. Unless there is a way to change the cap to fit the fuel filler neck, is there?

 

[3393RP]

Better check your muffler bearings quick before your plane blows up!

seriously though. There’s no fuel in that hose 99.9999% of the time, so not sure how critical this is.

Gasoline leaks aren't the only issue. The hose is critical for proper vent operation, and sometimes when they deteriorate like that, it results in an interior blockage.

It should serve as an eye opener with regards to all hoses (including hydraulic) on an aircraft. Some are in places that are difficult to access, and based on experiences posted by Dan and others, there are planes out there that have never had hoses replaced.

It would behoove owners to look at the OP's photo and wonder if their aircraft has hoses in a similar condition.

 

[Magman]

#1 Ignored Hose in my book is the short Oil Pressure Hose on many Piper Aircraft.

Typically 30 to 60 years old!

They are kind of pricey as they have an Orifice incorporated in the assembly.

Also in the running is the short Brake Hose at Landing Gear Attach Point

on Colts and Tri-pacers.

“They are working fine” ; until they don’t.

 

[Dan Thomas]

That is an interesting fact. One of my caps is aligned fore-aft, the other is clocked differently. So at least one should have worked correctly. My fuel tanks have a 6 (or 8?) bolt hole pattern fuel filler neck. One of those must have been improperly indexed when installed as that determines which way the cap sits when tightened. Unless there is a way to change the cap to fit the fuel filler neck, is there?

I couldn't find a parts manual for a vintage 150, but here's the stuff on old 172s. It's similar:



Yours is likely the main diagram, with the threaded filler neck. It screws into a boss riveted into the tank. Mechanics make the mistake of screwing it in until the cap tab slots are fore-aft, which leaves the cap at the wrong angle. By the time they discover their mistake the sealant has set. Note, in the picture, how the slots are at around 2 o'clock and 8 o'clock, not fore-aft (6/12 o'clock). You stand a chance of tearing the boss rivet out, or tearing the tank trying to re-index that filler neck. Rust also seizes it in there. The neck is steel, the boss is aluminum. Dissimilar metals galvanic corrosion. That little well catches rainwater and snowmelt and adds to the corrosion issues.


It's worse if it's messed up on the right tank. That tank is vented to the left tank via a crossover line between the two, and that line is full of fuel when the tanks are full. It hampers equalization of pressures. That's why the AD that mandates vented caps says that a vented cap must be installed at least on the right tank. Most ended up with vented caps on both.

 

[Gary Ward]

Thanks for the heads up, I think it is a good reminder for all of us.

 

[GeorgeC]

The vented caps must be oriented properly, too, with their handle fore and aft. Old airplanes had screw-in fuel filler necks that sometimes got turned a bit and then seized there. It puts airflow against the two small static vent ports in the cap handle and messes up the tank pressures. Those ports are important to avoid the low pressure over the wing from holding the fuel back.

Sigh. I thought it was just an infuriating OCD trigger. Both of mine are clocked wrong.

 

[BoButt]

Interesting thread. Might add it to the Hundred most missed at annual list.
One question. Is using a heat gun on or in around possible fuel vapors a bit dicey?!

 

[Skip Miller]

No. It is very dicey.

Most heat guns have a minimum heat of around 500 degrees F. Auto fuel has a flash point of 500 - 530 degrees F. Don’t use a heat gun near liquid gasoline. Period!

-Skip

 

[Witmo]

You can actually lose a good chunk of fuel if the airplane is parked on a slope with the left wing low. The fuel from the right flows through the system to the left tank and out the vent. If the vent check valve inside the tank is stuck open it will run out like crazy.

McFarlane sells a vent line with a high spot in it to discourage that.

There is an AD that mandates vented fuel caps for the Cessnas, to prevent power loss if the vent is blocked

If I recall, the AD for the 150 requires a vented fuel cap only on the right wing. You'll see a lot of Cessna 150/152s with both wings having vented fuel caps because Cessna stopped making unvented fuel caps long ago which limited your choices for replacing one.

Even with the McFarlane fuel vent line, you'll see fuel dripping from the vent line when taxiing around with full tanks and making a sharp right turn. Even so, I highly recommend the McFarlane vent line as it has paid for itself many times over. Installing one is a good time to inspect and or replace the small rubber hose mentioned earlier as well as the metal strap and guard that secures the fuel tank.

 

[BoButt]

Not to be picky, however, The flash point of auto fuel is -45ºF. The auto ignition temperature is (536ºF) the minimum temperature required to ignite a gas or vapor without a spark or flame present. 100LL has a flashpoint of -40º F/C. according to Shell. Actually varies with the junk they mix in it. Just threw that in because of the -40 = -40 phenomenon!

 

[Gary Ward]

Interesting thread. Might add it to the Hundred most missed at annual list.
One question. Is using a heat gun on or in around possible fuel vapors a bit dicey?!

No. It is very dicey.

Most heat guns have a minimum heat of around 500 degrees F. Auto fuel has a flash point of 500 - 530 degrees F. Don’t use a heat gun near liquid gasoline. Period!

-Skip

That is very bad advice from OP IMO. Never should you use heat around fuel lines especially in our airplanes!

 

[Dan Thomas]

That is very bad advice from OP IMO. Never should you use heat around fuel lines especially in our airplanes!

Yes. I had missed that. This is the sort of thing advised by people with no training, and it sometimes results in disaster of some sort. Even if the heat didn't start something, the sparks made by the heat gun's motor brushes could do it. It's why aircraft shops use air-driven tools, after all. Fuel vapors could be anywhere, especially inside wings.

 

[MajorTurbulence]

My IA recommends replacing that one and all fuel hoses, clamps and inspecting and/or replacement of the fuel sender gaskets for leaks inside the wings of my PA28 after every 6-7 years as part of my annual. After 4 hrs labor per side, and no sqwalks about fuel smell or anything before the annual, telltail blue stains were seen from a fuel sender gasket. So now, since everything has been replaced, the 6-7 year timer starts again.

 

[Gary Ward]

That isn't an overflow. It's the tank vent, for both tanks, and it's critical. Cessna publishes positioning information behind the strut for that thing, to get the right amount of head pressure in the tanks.

View attachment 97961

There are also short pieces of rubber hose in the vent crossover between the tanks. They're miserable to get at. The tank covers have to come off and you might even have to get the headliner out to get at the clamps inside the ceiling. They rot, and I have had fuel running down the doorposts of an old Cessna because those things rot away.

View attachment 97962

These pics are from the '69-'76 150 manual. Check the manual that applies to your model year.

Replaced these 6 rubber pieces yesterday in my 1980 172N inside the cockpit. You must remove the headliner and wing root fairings to get to them. Mine were 42 years old and very stiff and stuck on.

I carefully used new razor blades and WD40 ,PBblaster to get them off without bending or breaking anything. It is quite the challenge replacing them.

I also replaced the scat hoses for the rear passenger air vents. Mine were broke, repaired and blocked with mud daubers.

Getting rid of more duct tape off my plane.

New air ducts were installed, the old ones were broke.

This is just a fit up, not done yet. There are all new rubber on my vent lines now!!

Got plenty of scat hose for both sides.

 

[Jeff767]

Hoses should be replaced on a routine cycle. I think the manufacturers of most hoses call for every 5 years. You can’t tell internal hose condition from a external inspection. 5 years is probably early but if my aircraft had hoses over 8 years old I would replace them. There are aircraft flying with really dangerous hoses. The aircraft I purchased 2 years ago was built in 2005 and the hoses I suspect were original. They looked ok but inspection after pulling them showed they were past there sell by date!

 

[Dan Thomas]

Cessna wants the fuel tank bays opened and everything inspected every 1000 hours. In some manuals it was 1000 hours or three years, whichever came first. Most never get it, not even in 40 years and 10,000 hours. We used to find the rubber strips under the tanks and on the hold-down straps rotted right off, and the tank chafing on its supports and the straps. Sometimes the tank gets chafed right through; that gets expensive.

Replacing those short hoses was a lot easier with the tanks out.



Every 100 hours for the hose inspection is overkill, but yearly, at least, is wise. Judging by the numbers of rusted-in screws in fairings and inspection panels, and the rotten stuff above headliners, this stuff usually never gets checked. Never.

 

[Jdm]

Replaced these 6 rubber pieces yesterday in my 1980 172N inside the cockpit. You must remove the headliner and wing root fairings to get to them. Mine were 42 years old and very stiff and stuck on.

I’m doing the same job. Question for you.. The 3’ fuel line located behind the ceiling liner, right above the aft portion of the door. Did you have to drain the tank for that one, or were you able to work around that somehow? Thanks.

 

[Gary Ward]

I’m doing the same job. Question for you.. The 3’ fuel line located behind the ceiling liner, right above the aft portion of the door. Did you have to drain the tank for that one, or were you able to work around that somehow? Thanks.

I had the tanks low and jacked up one side at a time so the remaining fuel ran to the other side.

 

[Gary Ward]

Hoses should be replaced on a routine cycle. I think the manufacturers of most hoses call for every 5 years. You can’t tell internal hose condition from a external inspection. 5 years is probably early but if my aircraft had hoses over 8 years old I would replace them. There are aircraft flying with really dangerous hoses. The aircraft I purchased 2 years ago was built in 2005 and the hoses I suspect were original. They looked ok but inspection after pulling them showed they were past there sell by date!

I agree, on cars and trucks rubber hoses are only good for 5-7 years. Why do we neglect them on planes?

I owned this plane for 3 years and been wanting to replace them since. It is annual time, so while the interior is out I got it done yesterday. My IA has been in and out over seeing me. We do the annual together at my hangar. I have worked on pretty much the whole plane by now.

I also agree that the tanks need to be inspected inside the wing and that rubber be replaced. I did not replace the rubber hose on the discharge at the bottom of the tank. I believe you need to remove the tanks to do that? That is a job for another day.

 

[Dan Thomas]

I had the tanks low and jacked up one side at a time so the remaining fuel ran to the other side.

You can run the tanks low, shut the selector off, and not have to run the fuel across at all. Just jacking one main up high enough will put the fuel away from the outlets on the low side.

 

[Initial Fix]

Different plane than I have now, but that one needed a new engine. So while we waited for the rebuild we did some “while we’re here” maintenance. We found fuel lines were original (50 years old) and pretty much fell apart. That was eye opening.

 

[Jdm]

I’m sure you know, but the Cessna p/n for the little 3” hoses has changed to a new p/n. The new one crosses over to a vacuum AND fuel hose. Be sure to get the fuel hose and not the vacuum. AirPower notified me of this when I ordered and made certain that I had the right item for the job.

BTW: I picked up a 172 in the Mississippi Delta once due to an old engine fuel hose that ruptured. The guy landed in a field. We had to yank the wings and trailer it out.

Flexible flammable fluid lines should be changed every 5-7 years according to most recommendations. Especially the one’s that are located forward of the firewall.

I Just finished a prebuy on an A36. The owner insisted that it was in tip top shape, and that all work was done by the best mechanic that ever lived. Of course we found numerous illegal items, out of date inspections, etc. The engine hoses were 26 years old. Some people are just idiots!

 

[Dan Thomas]

I Just finished a prebuy on an A36. The owner insisted that it was in tip top shape, and that all work was done by the best mechanic that ever lived. Of course we found numerous illegal items, out of date inspections, etc. The engine hoses were 26 years old.

I went to do a prebuy on a 172 we wanted for the flight school. "Just out of annual," we were told. Found two of the four exhaust risers cracked almost all the way around just below the cylinder flanges. Had to travel the eight hours home, order the stacks, then go back out and put them on and fly it home. Pulled the engine right away, since it was the original and was past TBO and was going to commercial registry, and the hoses were all originals, 30 years old. Hard as wood, rusty steel braid. Also numerous other things not easily picked up on a three-hour prebuy. Bought it knowing we were going to spend serious money on it. You pretty much have to assume that on old airplanes.

 

[Jdm]

Yep, and people complain about paying for a good prebuy some prefer to get an annual instead. Usually have to bite my tongue on that subject.

I had to make 2 trips across the country to get the A36 home also! I’ll usually spend at least 2 days on a really good prebuy. Sounds crazy I know, but I select my customers appropriately, and they want to know exactly they’re getting into.

Great discussion but I don’t want to to hijack this great fuel hose posting.

Good job on the fuel hoses! Thanks for sharing your information.