Oh Boy, fuel leak!

[Glen Davis]

Well today I found a small blue stain coming from one if the screws securing an oval panel closest to the fuel petcock in my 84 J. There was also a small stain around the petcock itself.  I wiped it off then flew for an hour. After landing is when I took this photo. There was no drip or actual liquid present, only the blue stain. How bad is this and what should I expect regarding its progression.  Glen

[RobertGary1]

The manual has examples in how to grade fuel leaks. This wouldn’t qualify as an airworthiness issue. It’s also pretty easy to fix.
 

-Robert  

[Glen Davis]

Service manual or POH?

[GeeBee]

I had one of those, and month later, it fixed itself. Don't be in a big rush.

 

 

[carusoam]

Good news...

That is a leaky fuel sample valve...

Often, the leak is a piece of dirt that has gotten into the working parts...

Press the sample cup up into the valve and work it....

always good to have a spare on hand for this... 

The valve has a large size for strong tools... don’t be fooled... if you use the proper tool, you can easily torque the valve’s head right off...

It has a rubber seal so its proper torque value is pretty small...

Have you seen any rust bits in the bottom of the fuel sample cup? (Not typical of M20Js...)

Best regards,

-a-

 

[RobertGary1]

1 hour ago, Glen Davis said:

Service manual or POH?

Service manual

 

[Guest]

1 hour ago, Glen Davis said:

Well today I found a small blue stain coming from one if the screws securing an oval panel closest to the fuel petcock in my 84 J. There was also a small stain around the petcock itself.  I wiped it off then flew for an hour. After landing is when I took this photo. There was no drip or actual liquid present, only the blue stain. How bad is this and what should I expect regarding its progression.  Glen

Use some acetone to clean up the blue stains.  Remove the screw and cover it with Permatex aviation form a gasket, then reinstall.  The O ring under the drain valve is an MS29513-014.

Clarence

[larrynimmo]

I have also stopped very minor leaks by coating the area with EZLube.  For example I will spread it around the edge of the fuel sample valve...it will turn blue, but generally doesn’t drip or spread.  When I am under the plane I can occasionally get a whiff

[Yetti]

There is an O-ring on the back side of that.   There is a number on the front.  Get the number on the front and order a new one.  Fly the tank down.  No one will recommend a hot swap of those but if you are fast you will spill no more fuel than a bad day at the fuel pump.  The are not to be cranked down on or you will be in a world of "oh no" and have a torque value associated with them. Fire extinguisher/ don't do in the hangar.  Don't smoke.  Closed driver on professional course.

[Yetti]

But if it is the screw.   Dab of permetex #3 and reinsert and torque properly.

[StevenL757]

On 11/29/2020 at 5:09 PM, RobertGary1 said:

The manual has examples in how to grade fuel leaks. This wouldn’t qualify as an airworthiness issue. It’s also pretty easy to fix.

-Robert  

Agree.

@Glen Davis, on a scale of 1 - 10 with 10 being the worst, this is like a "1.5"  Observe and continue to report.  If it grows to a drip, then I'd plan to have the panel removed and patched, but at this point, nothing to worry about.

[carusoam]

Reviewing the thread...

There may be two ‘leaks’...

1) the sump drain/fuel sample valve....

2) a screw in the access panel...

 

Clean the area really well, as described above... to see what is actually asking for help...

Swapping out sump drains is easy...
 

Resealing individual screws is easy...

To do these... it really helps to have the tank empty first...

PP thoughts only, not a mechanic...

Best regards,

-a-