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Tank leak at sending unit?


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My pilot side tank on my E model has a minor leak and judging from the smell inside and location of blue stain under the belly, I feel it very well could be the gasket around the sender. Is this easily accessed from inside or do I need to take off belly skins?

Edited by nels
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The "inner' senders are accessed from inside the cabin, behind the side wall carpeting, just under the door (and the similar area on the pilot side). The outer ones from an inspection cover out under the wing. If you smell it in the cabin, it is likely the inner one.

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Inside access.  Easy to see after removing the sidewall materials.  Remember all the safety guidance before allowing your mechanic to work on it...

Yes, it is safety overkill.  A couple of Mooneys have perished in fuel related fires at the hands of new (to Mooney) mechanics.

post pics...  Especially if there is a lot of blue goo residue...

Best regards,

-a-

 

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7 minutes ago, DonMuncy said:

The "inner' senders are accessed from inside the cabin, behind the side wall carpeting, just under the door (and the similar area on the pilot side). The outer ones from an inspection cover out under the wing. If you smell it in the cabin, it is likely the inner one.

So, there are two senders per tank?? I smell it in the cabin but not really so much as I would expect. It appears to be way inboard on the wing right at the belly.

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On some Mooneys there are two...

My C only had the inner ones.  They leaked enough to turn the carpet blue.

Didn't have MS at the time.  Would have fixed it a whole lot sooner than waiting for annual to look into it.

Best regards,

-a-

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Yes, each tank (at least in later years; I don't know what they did early on, or when it changed) has one on each end of the each tank. Neat, as the end result is that your gauge is reading the average of each sender, so even in a bank, you still have some semblance of accuracy. Neater yet is the electrical circuit (which you need to be aware of if removing a sender). The "hot" from the master runs to one side of the cabin gauge. From the other side of the gauge, the wire runs to the terminal of the inner sender. That terminal goes through the rheostat type wire in the sender, which then goes to the "body" of the sender. The body is insulated from the tank by non-conducting washers, but the body is connected by a wire to the terminal on the outer sender. That terminal runs through the rheostat type wire to the body which is grounded to the tank. This, of course, lets the gauge read the variable ground of the two senders.

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Well, I went down to the airport a few hours ago, I took out the pilot seat, window trim mid trim and lower trim. That was all fun...not. Anyway, the sender is not leaking. It's raining so crawling under the wing and taking off access panels to look for another sender was not going to happen. At least not today.

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So no fuel in the cabin? There's no need to pull the bottom access panels.....yet. You can probably find the leak by pulling the top access panels and following the instructions on Don Maxwells website. Bad news is the sending unit gasket leak is an easier fix.

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  • 5 years later...
2 hours ago, lithium366 said:

My fuel sender has some kind of sticky goo on it around bolts and sender flange. My guess it’t to prevent small leaks at bolts. Does anyone know what product it can be? I need a bit more of it

What color is the sticky goo? If it is pink or grey it is probably tank sealant. If it is red it is the red butyl rubber sloshing compound. 

Or it could be damn near anything else somebody used.

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2 hours ago, N201MKTurbo said:

What color is the sticky goo? If it is pink or grey it is probably tank sealant. If it is red it is the red butyl rubber sloshing compound. 

Or it could be damn near anything else somebody used.

It’s brown and it is a sticky

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Dark brown and sticky can be fuel residue.... when the leak has been carrying on for some time, it’ll get it the point where it looks almost black.

Brown and sticky could also be sealant that did not cure properly. It is not terribly uncommon to find instances of sealant that did not cure. I’m guessing you’re looking at an old, ongoing fuel seep, though... a pic sure would help.

Edited by PilotCoyote
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Ilya,

Its a good chance that it is an old fuel leak...

Brush up on the screws, gasket, sealant that gets used for individual screws... and the proper torque to be used...

Getting everything torqued evenly is probably the important part...

Could be a quick fix...

 

While you are in there... have a look at the connector tube... rubber tube from tank fuel line headed towards the fuel selector switch...  age related health issues....

Good news... low cost fixes for expensive challenges... :)

Pp thoughts only, not a mechanic...

Best regards,

-a-

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Permatex #3 is brown and if not installed correctly stays a bit sticky. I was able to grab some at local auto parts store. Aka- Napa, autozone, oreilly, car quest. Make sure you let it become tacky before installing, it needs that air time to set off reaction I believe. Good luck

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