M20J newly sealed tanks not venting right

[Guest]

10 hours ago, Barzook said:

Hi,

First time posting, but always reading. I have had my tanks stripped/sealed by a local shop (I was too far away from Minnesota/Florida vs my experience as a pilot). They had a hard time doing it right, it took many months. I've been flying and fueling the plane for 2 months now and something is not right.

When I fuel it up, I fill it to the edge of the gas cap. So when I put the cap on, it sort of displace some gas, just to give you an idea how full it is. If I come back a few hours later, the fuel level dropped by about 1'' in each tank. Right after fueling, we can hear bubbles making their way to the top of the tank. So if I fill it up and take it as-is the next day, I don't have 32 gallons in each tank but more like 30 gallons probably. Which is a problem for me, I want my full 32 gallons.

What I think happened is that they sealed the upper section of the ribs where there's supposed to be seap-holes to let the air exit in between the tank sections (3 on an M20J per tank, so 2 dividers). There's probably still some openings, so in the end the fuel takes the place of the air and the air gets vented at the top of the tank, but this takes a while.

I think I need to have this reworked to enlarge these holes and would like to have a picture of what it's supposed to look like. That shop will not take the plane anymore, they have had it. So I'd like to document the problem as good as possible to try to find another shop who could do the rework.

Let me know what you think and if you have any pictures of that I'd be very interested too.

Thanks for your help!

Drain or use the fuel to empty the tanks.  Insert a video scope camera through the fuel filler and examine the ribs.  If indeed the vent holes are covered over you’ll have to open the tops of the tanks to clear the holes.

If Rich isn’t able to get pictures, you can contact Mooney tech support, they will be able to confirm how many holes there should be.

Also the shop should have signed out compliance with AD85-24-03 and SBM20-230A

https://wwwapps.tc.gc.ca/Saf-Sec-Sur/2/AwD-CN/documents/US85-24-03.htm

https://www.mooney.com/wp-content/uploads/2020/12/SBM20-230A.pdf

 

[Barzook]

51 minutes ago, M20Doc said:

Drain or use the fuel to empty the tanks.  Insert a video scope camera through the fuel filler and examine the ribs.  If indeed the vent holes are covered over you’ll have to open the tops of the tanks to clear the holes.

If Rich isn’t able to get pictures, you can contact Mooney tech support, they will be able to confirm how many holes there should be.

Also the shop should have signed out compliance with AD85-24-03 and SBM20-230A

https://wwwapps.tc.gc.ca/Saf-Sec-Sur/2/AwD-CN/documents/US85-24-03.htm

https://www.mooney.com/wp-content/uploads/2020/12/SBM20-230A.pdf

 

Thanks M20Doc, that's very good information. I'm not sure I've seen this written in the log book, I'll double check.

[N201MKTurbo]

1 hour ago, Barzook said:

Thanks M20Doc, that's very good information. I'm not sure I've seen this written in the log book, I'll double check.

FWIW, don’t take off the top covers to fix it, take off the bottoms. The paint damage won’t be as obvious and it’s easier to work on the top of the tank through the bottom covers. You can get to all the holes through the center cell, so no need to take off more than that.

I contacted the guy I was supposed to help today and he is out of town till next week, so the pictures will have to wait.

[Barzook]

2 hours ago, N201MKTurbo said:

FWIW, don’t take off the top covers to fix it, take off the bottoms. The paint damage won’t be as obvious and it’s easier to work on the top of the tank through the bottom covers. You can get to all the holes through the center cell, so no need to take off more than that.

I contacted the guy I was supposed to help today and he is out of town till next week, so the pictures will have to wait.

Thanks for the tips, you are perfectly right about the center cell, I didn't think of that!

[Pinecone]

14 hours ago, Fly Boomer said:

Mine is a 252 with the cursed flappers on the main tanks, so I guess that accounts for the difference.  Thanks.

I wish there was a way to remove the flappers.

[Fly Boomer]

22 hours ago, Pinecone said:

We filled the inboard filler on one side, then filled the outboard (Monroy).  Then did the other side.  Then back to the first side to fill the outboard again after the fuel migrated to the inner (original tank).  then back to the other side.  We did one more round, then headed to lunch.  After lunch, we put in another 9 gallons total.

Does the hydraulic head created by the fact that the Monroy tank is higher (further out on the wing), ever push gas out of the fuel vent?

[Fly Boomer]

3 hours ago, Pinecone said:

I wish there was a way to remove the flappers.

Paul Maxwell told me they can get rid of them, but I'm too cheap.

[Barzook]

Thanks for your input everybody, I've borrowed a borescope and will check if all the holes are where they're supposed to be.

[Pinecone]

20 hours ago, Fly Boomer said:

Paul Maxwell told me they can get rid of them, but I'm too cheap.

I wonder how much?

[Barzook]

Quick update, a mechanic came and cleared all the bottom and top holes. Turns out less than half were still there. He had to open all the top panels, mainly because it was easier to work from the top and because he wanted  access to both sides of the rib to make sure there's no loose PRC and then vacuum everything. I fueled it up this afternoon, and looks like there's no more air pocket during fill up. Problem solved. Thanks everybody for your help!

[carusoam]

Great follow up Barzook!

Thanks for sharing the details!

Best regards,

-a-