Fuel tank vent lines

How to keep the Cessna 170 flying and airworthy.

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Re: Fuel tank vent lines

Postby brian.olson » Thu Sep 13, 2018 12:07 pm

Dave:

As you sit in the pilot's seat, if you look straight up above your right shoulder that is the view you will see in the photos above your post. It's hidden behind the headliner. The speaker points rear, and the silver bar you see at the top of the photo is towards the windscreen.

Edit: BTW - and I may be jumping to conclusions here - if you are chasing a fuel fume issue there is something you can quickly check before starting to rip off the headliner. Run your fingers around the outside of both fuel gauges, just behind the screws. A few months ago I had some very faint fumes when I first entered the plane and after scratching my head for awhile found just enough wetness around (both) the gauges to cause the smell, but not enough to be detected as a leak or staining. I gave each of the four screws a tighten (the bottom two on each side moved about 1/16 of a turn, the top two on each side didn't budge) and it was enough to fix the issue. I suspect at some point I'll need to have the mechanics replace the gaskets but for now - issue solved and no smell.
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Re: Fuel tank vent lines

Postby Bruce Fenstermacher » Thu Sep 13, 2018 12:33 pm

Hard to say where the smell is leaking from when it does but as you can see there are rubber fuel line couplings both as pictured and at the other end of the metal fuel line at the tank. It is assumed when no other source is found that it must be coming from them.

These look easy to change but in fact it is a real pain in the but because the metal fuel line is such a close fit between the tank and the J breather than one must loosen and slip the rubber line back over the fuel line so it can be slide carefully out of position. Of course on removal you can cut the rubber from around the fuel line. But on replacement you must slide the new rubber on the line then place the line in place and slide the rubber line over the splice. And we haven't even discussed temporarily removing the front of the headliner and then replacing it. This is a simple job that has many simple steps that all together can be time consuming and knuckle busting.
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Re: Fuel tank vent lines

Postby gfeher » Thu Sep 13, 2018 12:49 pm

As others mentioned it's at the top center of windshield right behind the carry through spar. Take off the trim piece that goes the full span left and right immediately behind the top of the windshield. Then peel back the front of the headliner. It should be flexible enough for you to peel it back. You should then see the two rubber hose connections right there in the center below where the external gooseneck vent is located. Although the thread in this link refers to a '52 B model, it's also applicable to your A model and provides additional good info on this repair that will save you a lot of aggrivation: viewtopic.php?f=24&t=13969&hilit=Fuel+tank+vent+line
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Re: Fuel tank vent lines

Postby gahorn » Thu Sep 13, 2018 4:13 pm

iowa wrote:hello
where is this linkage located on the airplane?
I think I need to fix mine as well
dave


Dave, … You see that overhead cabin-speaker in those photos...? :wink:

By the way folks.... those are NOT automotive hose-clamps found at AutoZone. Use only Genuine Aircraft-Quality hose clamps, such as Breeze Aero-Seal available from aircraft suppliers: https://www.aircraftspruce.com/search/s ... ps&x=0&y=0

The difference is the Aero-Seal aviation quality clamps are built such that better screw-worm engagement and mechanical retainers are included to prevent vibration/destruction and greater torque capability. Automotive clamps may be lesser-grade/temper materials and less attachment security of the screw/worm.
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Re: Fuel tank vent lines

Postby Kevin Pearce » Wed May 15, 2019 7:52 am

I am fitting my 1953 170B wings this weekend, does anyone remember the length of the outboard rubber hose?
I can measure and work it out but would be nice to have a comparison number.
I am planning on pre-fitting the hose on the wing and sliding onto fuselage pipe as the wing is fitted.

Thanks
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Re: Fuel tank vent lines

Postby Bruce Fenstermacher » Wed May 15, 2019 10:56 am

Kevin, on the A and B model, the outboard (at the tank) hoses are only a few inches like those shown in the photos at the vent T earlier in this thread.

Haven't tried it but I'd think lining up the wing with the vent line already installed in the wing, would be a hand fuel of things to line up. The vent lines I've changed hose one are made very tight and close fitting.
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Re: Fuel tank vent lines

Postby DaveF » Wed May 15, 2019 4:23 pm

I don’t think you’ll be able to slide the vent tube into the hose as the wing is going on. The fit of the hose is much too tight to allow it. I haven’t installed a wing, but I have done the fuel tanks. The short outboard section of hose that fits on the tank is difficult to get in place. Even with lube, it takes a lot of twisting and pushing.
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Re: Fuel tank vent lines

Postby Bruce Fenstermacher » Wed May 15, 2019 4:31 pm

What Dave said I will emphasize. This is another "looks easy" job that will have you cussing the Cessna engineer who came up with it.
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Re: Fuel tank vent lines

Postby c170b53 » Thu May 16, 2019 4:27 am

It may be the way I hold my tongue, but new hose, petroleum and Bob’s your uncle. Push-twist the new rubber lines onto the center lubed alum.tubing just enough so the wing and strut bolts can be planted. Pull/push the tube outboard to connect to tank. Should be fairly straightforward and I’ve not found it too hard. I some times use long needle nose pliers spread enough to push the tube by the tube ends
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Re: Fuel tank vent lines

Postby Bruce Fenstermacher » Thu May 16, 2019 11:42 am

c170b53 wrote:It may be the way I hold my tongue.


Yes yes, that MUST be it. :D
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Re: Fuel tank vent lines

Postby gahorn » Thu May 16, 2019 9:16 pm

WD40 helps. :wink:
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Re: Fuel tank vent lines

Postby Kevin Pearce » Sat May 18, 2019 5:10 pm

Thank you all for the advice. The slide on with wing worked well along with WD40.
I used LPS3 on the bolts and attach points
The wings are now fitted with bolts in place, washers, nuts and cables to run tomorrow.
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Re: Fuel tank vent lines

Postby DaveF » Sat May 18, 2019 5:19 pm

Good to see.

I guess I should have used WD-40! :D
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Re: Fuel tank vent lines

Postby johneeb » Sat May 18, 2019 6:45 pm

Kevin Pearce wrote:Thank you all for the advice. The slide on with wing worked well along with WD40.
I used LPS3 on the bolts and attach points
The wings are now fitted with bolts in place, washers, nuts and cables to run tomorrow.

Kevin,
Is that a sheet rock (drywall) hanging jack there in your hangar? Did you use that to install your wings and if so how did it workout?
John E. Barrett
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Re: Fuel tank vent lines

Postby Kevin Pearce » Sat May 18, 2019 8:43 pm

John
Yes it is, well spotted.
It worked very well, we used it at the wing root first and it lifted the wing well. The wheels allowed us to line up the attachment lugs and slide the wing into place. You can finely adjust the height. We then removed the fixed trestle and positioned it outboard of the strut and used it to lift the wing high enough to slide the strut into the wing and then lower with precision. We raised the tail so the wing incidence was fairly level and the stand allows some adjustment as you slide into place. Two stands would allow the dihedral to be set earlier and less helpers required.
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