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Thread: Cessna 180 Fuel Vent Issue

  1. #1
    Steve Pierce's Avatar
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    Cessna 180 Fuel Vent Issue

    Lance came up in his 1954 Cessna 180 with the update cross over fuel system earlier in the week. When he got here we noticed that there was a fuel stain aft of the right fuel cap and the supper area was full of fuel. When we looked inside the 2 year old bladders were sucked in. When the fuel was drained there was 10 gallons instead of the 29 gallons that the fuel flow gauge said was suppose to be there. Checked the two vented gas caps and the vent behind the left lift strut. Got the bladders back flat and as wrinkle free as possible. Can't figure out how and why this happened.


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  2. #2

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    I think the early 180 had a non-vented cap on left tank. Are both caps vented type? Could have switched with non-vented on right and crossover sucked fuel/air out.
    DENNY

  3. #3

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    The length the vent behind the strut sticks down is CRITICAL, make sure it is correct.

  4. #4

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    The same thing happens when you fly a 180 without a fuel cap. Maybe the cap wasn't seated properly. The vacuum sucks fuel out and the bladder lifts so the gauge reads full. One clue from the driver's seat is that the gauge reads full when it shouldn't. Maybe it applies here, maybe not. It's the first place I'd look.
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    hotrod180's Avatar
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    Thead hijack....
    I hear about a lot of feeding / leaking overboard fuel issues on Cessnas which are equipped with the underwing vent.
    I usually see them puking gas out the vent when parked if they're anywhere near being full too.
    I rarely hear of any issues with the cabin-top vent.
    I've sure never had any with either my old 170 or my 180.
    I think the AD requiring the C180 top vent to be changed to a bottom vent if and when the LH bladder is removed for any reason is a bunch of BS.
    In this case, it seems to me that the cure is often worse than the disease.
    I've also heard that the service kit to do the new vent is hard to find or unobtainable to boot.
    OK, back to your normal programming...
    Cessna Skywagon-- accept no substitute!
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  6. #6
    www.SkupTech.com mike mcs repair's Avatar
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    look in the monarch cap thread recently here and i explain it, and fix...

    bottom line, you need to move vent more out into airflow to overcome this (lack of)internal tank pressure issue, irrespective of where the manual says to locate vent

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  8. #8
    180Marty's Avatar
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    I think the AD requiring the C180 top vent to be changed to a bottom vent if and when the LH bladder is removed for any reason is a bunch of BS
    I'm with you. If you move behind the strut out in the air stream like Mike says, it'll pick up ice there too.

  9. #9
    180Marty's Avatar
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    look in the monarch cap thread
    I'll have to tell on myself. About a year ago I flew around for about a half hour with my right Monarch cap off. The tank started out about 3/4ths full and I didn't lose a drop. The little flapper deal did its job. The reason the cap was off was because a gas boy broke the chain about 20 years ago so the cap was totally separate which was a good thing---it didn't bang up my wing when I took off.. I still have an out the top vent too.
    Last edited by 180Marty; 02-24-2017 at 01:44 PM.

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    Quote Originally Posted by 180Marty View Post
    I'll have to tell on myself. About a year ago I flew around for about a half hour with my right Monarch cap off. The tank started out about 3/4ths full and I didn't lose a drop. The little flapper deal did its job. The reason the cap was off was because a gas boy broke the chain about 20 years ago so the cap was totally separate which was a good thing---it didn't bang up my wing when I took off.. I still have an out the top vent too.
    You're lucky. Some years ago, one of our 185's took off with the gas cap hanging by its chain. It was immediately discovered and the pilot flew a short pattern and landed safely. The affected tank started out with 20-25 gallons and was dry on return.
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  11. #11
    www.SkupTech.com mike mcs repair's Avatar
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  12. #12
    180Marty's Avatar
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    You're lucky. Some years ago, one of our 185's took off with the gas cap hanging by its chain. It was immediately discovered and the pilot flew a short pattern and landed safely. The affected tank started out with 20-25 gallons and was dry on return
    That's why I'm a fan of Monarch and can't figure out why so many are bad mouthing them. I assume your 185 cap wasn't Monarch.
    Last edited by 180Marty; 02-24-2017 at 07:04 PM.
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  13. #13
    hotrod180's Avatar
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    Ive heard mixed reports pro/con on the monarch caps, thats why i decided not install the ones i had & just fixed the latches on the stock cap covers instead. No complaints now.
    Cessna Skywagon-- accept no substitute!

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    Check valve issues

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    ... or some knucklehead could have done this to the check valve upon installation, causing an "always open" situation.
    This is what we pulled from our right wing after full fuel fill caused fuel vent peeing. Noted it during pre-purchase, but figured it was just a poorly sealing check valve. It sure was...
    Based on maintenance records, the previous owner had put up with it for six years.
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  15. #15
    hotrod180's Avatar
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    Stuck-open check valve caused by....?
    Cessna Skywagon-- accept no substitute!

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    Quote Originally Posted by hotrod180 View Post
    Stuck-open check valve caused by....?
    Look closely at the pic of the valve end. See that plastic tubing sticking out?

    Installer had jammed the nylon cross vent line all the way through past the normal point, into the check valve assembly and out the flap. This is the nylon vent tube that connects to the crossover line that extends from the inboard end of each cell (see Fig. 12-3 and Desc. 12-21 in the CSM).
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  17. #17
    180Marty's Avatar
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    Boy, that seems like it would be difficult to do. My 54 180 has an aluminum tube running between vent nipples in the bladder and couldn't even reach the outer front corners.

  18. #18
    180Marty's Avatar
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    Just reread the first post-----Steve, did you and Lance get it figured out????? I filled my 54 right side fuel tank so full yesterday, that the Monarch flapper deal held a little bit of fuel when it was closed. After flying, there was no sign of fuel spewing out. I still have the original out the top vent.

  19. #19

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    Marty-
    It's a different system in the long range tanks. If further interested, take a look at figure 12-2 in the 1969-76 Cessna Service Manual for 180/185. You'll see the plastic vent tube extending across the cell.
    John
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  20. #20
    SJ's Avatar
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    I just want to confirm a couple things... I have the BOTTOM fuel vent on my '55. It sticks well down past the strut, in fact, about as far down as it can. This plane as Eagle bladders installed 15-18 years ago or so, so it's the original system with the flip up covers.

    I have a little seepage which shows up periodically out of the upper vent line on the OTHER wing from where the vent is, so thought maybe this should be move out of the airstream a little bit. What I read here would suggest I better leave it where it is. However, in my googling around, I can't figure out exactly where it "should" be. Any help appreciated!

    Thanks!

    sj

    $50 follow up question: Is that upper vent tube coming through the last wing rib on the right wing built into the bladder, or can it be replaced?
    "Often Mistaken, but Never in Doubt"
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  21. #21
    SJ's Avatar
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    Thanks to Steve Pierce for this... seems to clear it up!

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    "Often Mistaken, but Never in Doubt"
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  22. #22
    Steve Pierce's Avatar
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    Here is the text to go with that figure. When did the vent get moved from the fuselage to behind the strut. I know it was early on.
    Attached Files Attached Files
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  23. #23
    mvivion's Avatar
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    Quote Originally Posted by 180Marty View Post
    I'm with you. If you move behind the strut out in the air stream like Mike says, it'll pick up ice there too.
    If you’re flying in that much icing.......you shouldn’t be. Keep it out in the breeze.

    MTV
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  24. #24
    hotrod180's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    Here is the text to go with that figure. When did the vent get moved from the fuselage to behind the strut. I know it was early on.
    My information says 1956.
    Cessna Skywagon-- accept no substitute!

  25. #25
    18180's Avatar
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    I also have 55 with Eagle bladders installed in 2009. On long flights fuel would get down to 1/2 and then start going back up. On landing, fuel levels would correct. Never happened on shorter flights. Only one thing can make that happen...tank bottoms lifting float. I have adjusted the fuel vent to match the drawings ad nauseum and even made myself a template to check it on preflight. I attribute this phenomena to 1. the positioning of the vent tube causes a low pressure...or at least not enough head pressure to overcome the mechanical resistance of the flapper in the vent check valve. 2. To the flexibility of the Eagle tanks. They are very thin and pliable and as such collapse/lift easily.

    Improved since I have pulled the vent down about 1/2 inch into the airstream but still happens on occasion. What I have not done yet is put double sided tape under the tank near the float. Something I am hesitant to do since it will likely make it harder to smooth wrinkles....
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