Fuel Stains- When is it time to address?

[SARNorm]

Hi All- I am looking at a M20J to purchase. Both wing fuel sumps have blue stain around them, and I am assuming that they can be repaired with new o-rings or seals. But there are also a few ( 5 or 6) rivets under the left wing that are outlined in blue (see photo.) When is it time to address such an issue? What is your experience in the progression of fuel leaks once it is first noticed? Thanks very much for your input.

[JWJR]

Well those look pretty minor. I recommend you fly or have the plane flown an hour or two and see what those stains look like then. If it looks the same no worries at all imho. Flying will amplify the leak due to the pressure differential. As for timeframe- anybody’s guess really. If you like the plane have the tank inspected for sealant condition- sealant failure usually starts with tiny dirt like debris in the fuel strainer samples.


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[N201MKTurbo]

The maintenance manual has guidance, with pictures! 

[Guest]

36 minutes ago, SARNorm said:

Hi All- I am looking at a M20J to purchase. Both wing fuel sumps have blue stain around them, and I am assuming that they can be repaired with new o-rings or seals. But there are also a few ( 5 or 6) rivets under the left wing that are outlined in blue (see photo.) When is it time to address such an issue? What is your experience in the progression of fuel leaks once it is first noticed? Thanks very much for your input.

From the maintenance manual, they aren’t critical yet.  However leaving them for too long will damage the paint costing even money.

Clarence

[SARNorm]

Good stuff. Thanks.

[47U]

2 hours ago, SARNorm said:

What is your experience in the progression of fuel leaks once it is first noticed?

What year is the aircraft?  Is the sealant original from the factory?  Is there history in the logs as to a strip and reseal, or partial repairs?  If the sealant is old with no history of repairs then the stains might be indicative of impending sealant degradation.  If the sealant has been stripped and resealed since new from the factory, then a few rivets with minor stains might not be so much of a warning sign.  Regardless, spot repairs on individual rivets shouldn’t be a big deal and can buy you some time.

[SARNorm]

1979 M20J- No mention in logs of any fuel tank work, resealing etc. Looks like original sealant. Airplane has been hangared all of its life.

[Ragsf15e]

19 minutes ago, SARNorm said:

1979 M20J- No mention in logs of any fuel tank work, resealing etc. Looks like original sealant. Airplane has been hangared all of its life.

As they said, it’s considered airworthy by the description in the maintenance manual, but it’s going to need repaired or completely resealed at some point in the not too distant future.  If you’re buying it, you can certainly fly it, but add a reseal into the purchase price ($10-14k ish total for both tanks).  Wait time can be long at the highly respected places.

[RobertGary1]

1 hour ago, Ragsf15e said:

As they said, it’s considered airworthy by the description in the maintenance manual, but it’s going to need repaired or completely resealed at some point in the not too distant future.  If you’re buying it, you can certainly fly it, but add a reseal into the purchase price ($10-14k ish total for both tanks).  Wait time can be long at the highly respected places.

Not sure I agree with that. Could easily after 10-20 years left on the sealant. May need a simple patch at some time 

[Guest]

Those tanks are likely a simple repair, at this point it appears to be a stain.   I thought that standard J tanks were $3500-$4000 per tank for strip and resealing at most of the well known shops.

Clarence

 

[SARNorm]

So, in going through the logs - the aircraft has been flown only 80 hours in the last ten years, and 3 hours in the last 3 years. It has been stored in a nice hangar throughout that time, and annualed almost every year. I am concerned because of the lack of recent flight time. What specifically should I be looking at because of the inactivity?

[dlthig]

There is a thread here about idle engines. Your concern is rusty bits inside the engine. I know it's a seller's market, but it would be prudent to price it with a run-out engine. It sounds like a great barn find, but you'll need a fair bit of reserve cash for likely contingencies. Best of luck!

Also, I'd probably be willing to pay the seller to have it delivered. The engine would be my main concern. 

[SARNorm]

That is my concern. There was corrosion discovered earlier this year. The engine was disassembled, and "reconditioned" after removing some corrosion by Central Cylinder Service in Omaha. The paperwork looks good, and the compressions are great. But, could this still be a problem?

[dlthig]

I'll defer to Clarence when he checks in. Until then, if you can, I'd try to fly some patterns get everything moving and warm then change and check the oil and filter. Do you have an engine monitor? 

[Ragsf15e]

10 hours ago, RobertGary1 said:

Not sure I agree with that. Could easily after 10-20 years left on the sealant. May need a simple patch at some time 

Agree.  That’s why I said repaired or resealed.  It’s gonna need something.  It’s not going to get better by itself.

[Ragsf15e]

1 hour ago, SARNorm said:

That is my concern. There was corrosion discovered earlier this year. The engine was disassembled, and "reconditioned" after removing some corrosion by Central Cylinder Service in Omaha. The paperwork looks good, and the compressions are great. But, could this still be a problem?

Cylinders and compression can be fine while your lifters and cam are corroded. Advice above by @dlthig is prudent.

[DCarlton]

14 hours ago, SARNorm said:

Hi All- I am looking at a M20J to purchase. Both wing fuel sumps have blue stain around them, and I am assuming that they can be repaired with new o-rings or seals. But there are also a few ( 5 or 6) rivets under the left wing that are outlined in blue (see photo.) When is it time to address such an issue? What is your experience in the progression of fuel leaks once it is first noticed? Thanks very much for your input.

It's taken my stains and very slow seeps over 15 years to get to the point where I'm thinking about resealing.  It depends...  

[1980Mooney]

6 hours ago, M20Doc said:

Those tanks are likely a simple repair, at this point it appears to be a stain.   I thought that standard J tanks were $3500-$4000 per tank for strip and resealing at most of the well known shops.

Clarence

 

That is correct.  Houston Tank Specialists at Eagle Lake, TX (about 30 miles west of Houston) told me about a month ago that the cost was about $8,000 to strip and reseal the tanks on my J.  I have Monroy Long Range Tanks so that creates some additional work.  That was just a discussion on the phone and not a written quote so I would not be surprised if the real quote is higher. 

They have a process that circulates a solvent through the tanks.  They said in addition to opening all the wing panels that they pull the interior for full access to tanks and fuel lines, pick-ups, etc.  I think he said the process takes 5 weeks.  I believe that they had about a 4 month backlog at the time.

Edited November 21, 2021 by 1980Mooney

[1980Mooney]

15 hours ago, SARNorm said:

Hi All- I am looking at a M20J to purchase. Both wing fuel sumps have blue stain around them, and I am assuming that they can be repaired with new o-rings or seals. But there are also a few ( 5 or 6) rivets under the left wing that are outlined in blue (see photo.) When is it time to address such an issue? What is your experience in the progression of fuel leaks once it is first noticed? Thanks very much for your input.

I assume that picture is of the main wing skin seam just outboard of the main landing gear.  And I assume that is the stain from sitting a long long time (not an overnight stain after being cleaned recently with MEK or alcohol, etc.).

Did you open the access panels under the wing and examine for any internal leaks where the tank walls join the wing skins or the spar?  If there is no leaks, puddling or blue stains, I would say that this looks really minor and I would just fly it without attempting any repair.

I am dealing with a more significant leak on the left tank of my J currently.  I am going to try to have it patched first.  The problem is finding someone that actually knows what they are doing with repairing tanks on a Mooney.  And if the an unskilled person starts working on the sealant in the tanks they can just cause more problems than solutions.

Edited November 21, 2021 by 1980Mooney

[JWJR]

That is my concern. There was corrosion discovered earlier this year. The engine was disassembled, and "reconditioned" after removing some corrosion by Central Cylinder Service in Omaha. The paperwork looks good, and the compressions are great. But, could this still be a problem?

Was it just cylinder work or was the engine removed from its mounts and the case split for a IRAN ? Big difference here


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[Guest]

8 hours ago, SARNorm said:

That is my concern. There was corrosion discovered earlier this year. The engine was disassembled, and "reconditioned" after removing some corrosion by Central Cylinder Service in Omaha. The paperwork looks good, and the compressions are great. But, could this still be a problem?

Idle engines in the wrong environment can corrode.  Knowing the extent of the disassembly and repairs are very important.  If the case was split what was done internally, new camshaft or reconditioned?  New lifters or reground or none?  Cylinders honed and re-ringed, oversized or standard size?  
New bearings would be a normal requirement for reassembly, new connecting rod nuts and bolts only if the rods were removed from the crankshaft.  

Lots of details to inquire about.  The logs should have details and hopefully a parts list.

Clarence 

[SARNorm]

Thanks Clarence. The listed work was  done recently and the description on the bill says, "engine disassembled, cylinders honed, cleaned and inspected. Camshaft reground under CCS009 process specification. 8 each Tappet P/N:72877 exchanged, reconditioned under CCS798 process specifications. Crankcase R & R only. Bendix Fuel Servo complied with SB-PRS-107. Reassembled using listed parts under WO #19991. The engine has been test run and is approved to return to service." The compressions are 78, 78, 78, 77 cold. What do you guys think? The engine starts right up and sounds smooth.

[Guest]

If that work was all done recently, there should be little to worry about in the engine.  The sooner you start flying it the better it is for it.

Clarence

[ZuluZulu]

13 hours ago, 1980Mooney said:

That is correct.  Houston Tank Specialists at Eagle Lake, TX (about 30 miles west of Houston) told me about a month ago that the cost was about $8,000 to strip and reseal the tanks on my J.  I have Monroy Long Range Tanks so that creates some additional work.  That was just a discussion on the phone and not a written quote so I would not be surprised if the real quote is higher. 

They have a process that circulates a solvent through the tanks.  They said in addition to opening all the wing panels that they pull the interior for full access to tanks and fuel lines, pick-ups, etc.  I think he said the process takes 5 weeks.  I believe that they had about a 4 month backlog at the time.

$8000 for the mains and Monroys?!  That's half what I was quoted last year.

[dlthig]

10 hours ago, SARNorm said:

Thanks Clarence. The listed work was  done recently and the description on the bill says, "engine disassembled, cylinders honed, cleaned and inspected. Camshaft reground under CCS009 process specification. 8 each Tappet P/N:72877 exchanged, reconditioned under CCS798 process specifications. Crankcase R & R only. Bendix Fuel Servo complied with SB-PRS-107. Reassembled using listed parts under WO #19991. The engine has been test run and is approved to return to service." The compressions are 78, 78, 78, 77 cold. What do you guys think? The engine starts right up and sounds smooth.

That's more encouraging.