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Topic Options
#415685 - 10/12/21 02:18 PM Fuel Tank Woes...
BHarbour Online   content
Pilot in Command

Registered: 11/18/20
Posts: 263
Loc: AL
I've had a leaky right fuel tank on my 172D for a while now. A drip from the underside back screws of the gap seal. Not a steady drip, but a drip. It would start on fill up, and would not be there when I'd land on a cross country. I attributed this to a bad rubber hose on the vent tube between the wing and fuselage. The airplane was annualed two weeks ago and it turned out that the rubber hoses are all good on the vent tubes.

Of course...almost none of the screws in the panel were the correct type. I ordered the screw kit from ACS, but are there any diagrams of where the different screws go on the panel?

What are my options for repair or replacing the tank? Any of you guys gone through this?



Edited by BHarbour (10/12/21 02:46 PM)
_________________________
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#415687 - 10/12/21 05:52 PM Re: Fuel Tank Woes... [Re: BHarbour]
Joeman434 Online   content
Diamond Pilot

Registered: 02/20/14
Posts: 7707
Loc: Ocala, Florida
There should be plenty of used serviceable tanks out there. Get a part number.
_________________________
Do it right the first time.

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#415688 - 10/12/21 06:13 PM Re: Fuel Tank Woes... [Re: BHarbour]
Challenger1 Online   sad
Platinum Pilot

Registered: 03/23/16
Posts: 3136
Loc: Cincinnati, Ohio
Originally Posted By: BHarbour
I've had a leaky right fuel tank on my 172D for a while now. A drip from the underside back screws of the gap seal. Not a steady drip, but a drip. It would start on fill up, and would not be there when I'd land on a cross country. I attributed this to a bad rubber hose on the vent tube between the wing and fuselage. The airplane was annualed two weeks ago and it turned out that the rubber hoses are all good on the vent tubes.

Of course...almost none of the screws in the panel were the correct type. I ordered the screw kit from ACS, but are there any diagrams of where the different screws go on the panel?

What are my options for repair or replacing the tank? Any of you guys gone through this?



What screws are you talking about? The tank cover screws on top of the wing?

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#415691 - 10/12/21 07:41 PM Re: Fuel Tank Woes... [Re: Challenger1]
magman Online   content
Gold Pilot

Registered: 10/11/12
Posts: 1725
Loc: buffalo NY


Edited by magman (10/12/21 07:42 PM)

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#415692 - 10/12/21 07:46 PM Re: Fuel Tank Woes... [Re: magman]
Challenger1 Online   sad
Platinum Pilot

Registered: 03/23/16
Posts: 3136
Loc: Cincinnati, Ohio
Cat got your tongue? lol

Fun huh?

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#415696 - 10/12/21 08:34 PM Re: Fuel Tank Woes... [Re: Challenger1]
BHarbour Online   content
Pilot in Command

Registered: 11/18/20
Posts: 263
Loc: AL
The screws on the panel that's over the tank.

[/quote]

What screws are you talking about? The tank cover screws on top of the wing? [/quote]
_________________________
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#415699 - 10/12/21 11:13 PM Re: Fuel Tank Woes... [Re: BHarbour]
skyhawk3 Offline
Silver Pilot

Registered: 05/07/11
Posts: 974
Loc: Vancouver BC
There are about 4 different lengths. I just use 2 different lengths. The longest ones go along the fwd edge.

You could remove the tanks and pressure test it. If there is a crack or hole you can just get it welded. Lost of tanks have small weld repairs to them. Isuspect the leak may be comming from either the fuel xmitter gasket or the filler neck gasket. Both of those tend to go long periods without replacement.


Edited by skyhawk3 (10/12/21 11:15 PM)

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#415705 - 10/13/21 09:59 AM Re: Fuel Tank Woes... [Re: skyhawk3]
magman Online   content
Gold Pilot

Registered: 10/11/12
Posts: 1725
Loc: buffalo NY
Not again!

Is the tank actually the leak?


Edited by magman (10/13/21 10:00 AM)

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#415706 - 10/13/21 10:02 AM Re: Fuel Tank Woes... [Re: magman]
magman Online   content
Gold Pilot

Registered: 10/11/12
Posts: 1725
Loc: buffalo NY
A Welder experienced in welding very thin aluminum is needed.

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#415707 - 10/13/21 10:05 AM Re: Fuel Tank Woes... [Re: magman]
magman Online   content
Gold Pilot

Registered: 10/11/12
Posts: 1725
Loc: buffalo NY
Pressure Testing these tanks is scary

One method involves a condom over filler to avoid over pressure.

😲

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#415708 - 10/13/21 10:53 AM Re: Fuel Tank Woes... [Re: magman]
rkittine Online   content
Gold Pilot

Registered: 02/11/21
Posts: 1022
Loc: New York
I had one wing tank over the years that leaked and turned out to be a hole in the tank. The shop was able to weld it and it was fine after that.

Bob
_________________________
Robert Kittine
CFI,CFII, MEI
Sag Harbor and Manhattan, New York
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#415720 - 10/13/21 01:31 PM Re: Fuel Tank Woes... [Re: magman]
Challenger1 Online   sad
Platinum Pilot

Registered: 03/23/16
Posts: 3136
Loc: Cincinnati, Ohio
I have welded up fuel tanks over the years. I only use a 1/2 pound of pressure to pressure test them for leaks.

A LP gas pressure regulator works well as they are set for 11" WC which is 1/2 pound.

A cessna tank is really thin and I would be afraid to put 1/2 PSI into it, I bet a condom would be about the right pressure relief.

At one point I had this crazy idea that I was going to install a extended range tanks in my wings...Not!


I have been working on getting my screws loose as I want to inspect my tanks and replace the rubber stripping that they rest on so I don't wear a hole in my tanks. I have about 3/4 of the screws loose now. I have been working on them a little at a time. I soak them in rust penetrate and then re tighten them until I am ready to take the cover off. It is a tough job getting all those screws out without damaging the nuts underneath. This screw buster works real well with a little valve grinding compound on the tip.

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#415722 - 10/13/21 03:44 PM Re: Fuel Tank Woes... [Re: Challenger1]
magman Online   content
Gold Pilot

Registered: 10/11/12
Posts: 1725
Loc: buffalo NY
At one time I saw a scrap 172 tank pressure tested.

All was well but when walking away we heard a crunching sound.

The tank had sort of imploded and crunched itself into a ball!

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#415724 - 10/13/21 03:48 PM Re: Fuel Tank Woes... [Re: magman]
magman Online   content
Gold Pilot

Registered: 10/11/12
Posts: 1725
Loc: buffalo NY
Checking for leaks while installed I use Cessnas method.

Tanks FULL. selector BOTH

Jack one side.

Fuel will flow through Selector and completely fill lower tank.

Observe safety precautions.

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#415731 - 10/13/21 07:16 PM Re: Fuel Tank Woes... [Re: skyhawk3]
BHarbour Online   content
Pilot in Command

Registered: 11/18/20
Posts: 263
Loc: AL
Longest screws on the forward edge..ok...that's easy.

An update...my mechanic removed the tank this morning and it's got issues in four places. A crack on the top, the vent tube is surrounded by JB Weld at the joint with the tank, the baffle is loose, and the filler gasket needs replacing.

I found a tank in very good shape (baffle in good shape too) at Texas Air Salvage for the very low, low price of $1,495! I'm kidding of course about the low price. But I did buy it since it's in such good shape.

I found a tank at another place for $800, but there was a dent on top, the fuel exit tube was bent back a little, and there was no information on whether or not the baffle was good. The tank came from a wrecked airplane.

Hopefully there'll be no more issues with either tank.

Originally Posted By: skyhawk3
There are about 4 different lengths. I just use 2 different lengths. The longest ones go along the fwd edge.

You could remove the tanks and pressure test it. If there is a crack or hole you can just get it welded. Lost of tanks have small weld repairs to them. Isuspect the leak may be comming from either the fuel xmitter gasket or the filler neck gasket. Both of those tend to go long periods without replacement.
_________________________
K4VIB

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#415732 - 10/13/21 07:21 PM Re: Fuel Tank Woes... [Re: Challenger1]
BHarbour Online   content
Pilot in Command

Registered: 11/18/20
Posts: 263
Loc: AL
I...gently...used an impact screwdriver to remove the toughest screws. But most of the screws came out easily enough as the panel had obviously been removed in the near past and the tank had been repaired in situ with JB Weld.

Originally Posted By: Challenger1
I have welded up fuel tanks over the years. I only use a 1/2 pound of pressure to pressure test them for leaks.

A LP gas pressure regulator works well as they are set for 11" WC which is 1/2 pound.

A cessna tank is really thin and I would be afraid to put 1/2 PSI into it, I bet a condom would be about the right pressure relief.

At one point I had this crazy idea that I was going to install a extended range tanks in my wings...Not!


I have been working on getting my screws loose as I want to inspect my tanks and replace the rubber stripping that they rest on so I don't wear a hole in my tanks. I have about 3/4 of the screws loose now. I have been working on them a little at a time. I soak them in rust penetrate and then re tighten them until I am ready to take the cover off. It is a tough job getting all those screws out without damaging the nuts underneath. This screw buster works real well with a little valve grinding compound on the tip.
_________________________
K4VIB

Top
#415753 - 10/14/21 03:29 PM Re: Fuel Tank Woes... [Re: BHarbour]
Challenger1 Online   sad
Platinum Pilot

Registered: 03/23/16
Posts: 3136
Loc: Cincinnati, Ohio
Originally Posted By: BHarbour
I...gently...used an impact screwdriver to remove the toughest screws. But most of the screws came out easily enough as the panel had obviously been removed in the near past and the tank had been repaired in situ with JB Weld.


Cool I hope the replacement tank is in good condition for you.

I miss my late buddy who had a large hangar full of a 40 year collection of airplane parts. He had 4-5 planes himself and bought several wrecked 172 from insurance company's. He would either fix em or part them out. His family was not into aviation and sold the whole deal to someone I was told. I could not afford or have a place to put it all. He also helped me learn about 172s. He had several tanks out of 172s including that extended range tank that I borrowed to mess around with. I returned it to him before he passed. I bought my plane from him.



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