Fuel cap O-ring Replacement

[AlanA]

I am going to replace the o-rings on my fuel caps and have my mechanic sign off on it. Has anyone replaced these themselves? Is it as simple as it looks? I'd appreciate any tips. Thanks!

[RJBrown]

It is a simple as it looks. One of the $mall things that some shops use to pad an annual bill. http://mooney.free.fr/Mooney%20SB%20SI/229A.pdf The service bulletin is to CHECK the o rings annually not replace every year. Plus it is a SB not an AD. If your o rings get replaced at every annual you ARE getting ripped off.

[N201MKTurbo]

Yep, simple. You will need the two new o-rings and a new cotter pin. Unless you are just doing the big one, which is a little easier then typing this reply.

[fantom]

The smaller O ring is a bit trickier the first time. All four O rings - $12 10 minutes labor - $14 No water seeping in - priceless

[N757DL]

Actually if you just do a little research you cn find the MS #'s for the O-rings and it costs about 3 dollars from Aircraft Spruce for all 4. When I get home next week I will post the numbers. Those O-ring kits are a ripoff. Just my two cents.

Ryan

[jetdriven]

Those o-rings are cheap insurance annually for water intrusion into your fuel tanks. The Mooney M20 series suffers from a higher rate of fuel system caused accidents than others in their class.  FWIW, 35$ will get you the blue Flourosilicone o-rings which last 20 years. The bladder caps have them. They are also over 100$ for a set of those, but the MS o-rings in the stock caps are much cheaper.

[N757DL]

Just looked it up, the numbers are in the SB MS29513-010 (little inner one), MS29513-338 (big outer one) I would also replace them every year if your plane sits out side. They are cheap and if the are dryrotted it will allow water to leak into your fuel tank which can kill you so spending 3 dollars a year it worth it to me.

[DonMuncy]

Actually there is an AD on the fuel cap O-rings. But is written as a "one time" inspection. Since it really doesn't make much sense as a one time inspection, most everyone treats it like a yearly on-going one. It does not say you have to change them, just inspect them. But since it costs so little to change them, by the time you inspect them you might as well change them.

[Jamie]

One of my caps has a lever so hard to lift I have to stick a key under it and pry up. I'm not sure how to fix this but I'm guessing it happened when the seals were replaced last time.  I'm not sure, having never done it, but you might want to check this before installing the cotter pin.

[DonMuncy]

First make sure the cap is in the neck properly. It is very easy to misalign it putting it in.

If it is still too hard to lift the tab, remove the cotter pin and unscrew the nut on the bottom a half turn and try it. If still too tight, loosten it a little more. It is a feel kinda thing, but very easy to set right. You want it tight enough to seal well, but not so tight you have to use a tool to pry it out.

[Jamie]

It's definitely placed correctly. After reading a thread on here about a line guy wedging a cap, I've been careful about putting them on and have been removing / replacing them myself when getting fuel. One's fine, the other I can't lift without a stick or something.

 

You can't reuse a cotter pin, right? I'll have to find some more and then I'll give it a try. Thanks.

[DonMuncy]

My hangar elf insists on using stainless steel cotter pins, but isn't fussy about the source. 

[AlanA]

Thanks for the tips and part numbers. I found them on aircraft spruce.. Hope to get it done this weekend. Thanks again!

[danb35]

Here's a good write-up on changing the O-rings:

http://csobeech.com/files/O-RingChange.pdf

 

It's aimed at Bonanzas, but our Mooneys use the same caps.  Here's some more information about the blue flourosilicone O-rings that seal better and last longer, with part numbers and sources:

http://csobeech.com/o-Rings.html

[CoachTom]

_Jamie,

_{When you check your oil, let a drop off the dip stick slide down the center of the fuel cap lever when you have it open.  It should help keep things sliding.  If not, you have to take apart, remove corrosion from the stem which is most likely the culprit from water sitting on the cap, and reassemble with some lube. Then keep up the lubrication.}

_{Let me know how you make out...}

 

_TMcD

[Jamie]

Good idea. Thanks. I'll give it a try tomorrow. Easier than disassembling the cap.

[danb35]

Oh, and the issue was raised about the AD and the SB.  There's a service bulletin (M20-229) that "mandates" recurring inspections of the fuel caps.  In the US, of course, for Part 91 operations, service bulletins are always advisory, no matter how "mandatory" they claim to be.  However, there's also an AD (85-24-3).  In the "compliance" section of that AD, it states, in full, "Within 100 hours time-in-service after the effective date of this AD or at the next annual inspection, whichever occurs first, unless already accomplished."  There's no mention of any recurring requirement.

 

The AD mandates that the fuel caps and tanks be inspected IAW SB M20-229 and M20-230, respectively.  Some IAs take the position that by incorporating the "how" portion of those SBs, the AD also incorporates the "when".  IMO, that's contrary to the plain meaning of the AD, but I wouldn't put it past some FSDO inspector to read it that way.

[M20F]

Can you replace the O-Ring caps with bladder caps even if you do not have bladders installed? If a new set of caps for $200 works better would be interested in that solution as one of my caps is leaking quite a bit.

[jetdriven]

Can you replace the O-Ring caps with bladder caps even if you do not have bladders installed? If a new set of caps for $200 works better would be interested in that solution as one of my caps is leaking quite a bit.

 

No, the fuel caps for bladder installations are not the same and are not interchangeable with the stock fuel caps.

 

They also have O-rings, just they are over 100$ a set of 4.  You can buy the blue Flourosilicone o-rings for the stock caps for a lot less than that.

[carusoam]

When a 60's M20 is leaking severely, consider looking for rusty fuel necks. The strain of forming the pieces makes them susceptible to rusting through.

Changing the necks out with SS parts is a good idea in that case...not very challenging to get done, and definitely worth it.

Somebody with an extra airframe may have these parts already available??!

Best regards,

-a-

[N201MKTurbo]

My old Mooney a 67F had rusty cap sockets. I cleaned them real good with steel wool and then painted them with zinc chromate. 15 years later the chromate had not come off, there was no rust and they didn't leak.

[carusoam]

I cleaned mine real well and found the cracks... Too late.

Hope somebody learns from this combined experience.

Best regards,

-a-

[1964-M20E]

http://www.mcfarlane-aviation.com/Products/?CategoryID=1003&ID=2725030&Make=Mooney&PartNumber=CA38241

 

 

 

I was just looking around and McFarlane has the orings for the O&N bladder fuel caps. $43 ea.

 

 

[Marauder]

http://www.mcfarlane-aviation.com/Products/?CategoryID=1003&ID=2725030&Make=Mooney&PartNumber=CA38241

I was just looking around and McFarlane has the orings for the O&N bladder fuel caps. $43 ea.

Well, that is another savings of $14 (from Aircraft Spruce's price). Thanks! Wish they would get these down into the $10 each range. I would change them more frequently.

[bumper]

The large O-ring 338 in fluorosilicone is available on Amazon for about $10.5 includes shipping (prime) here: http://www.amazon.com/gp/product/B0055E1RLM/ref=ox_ya_os_product 

 

The little one, size 010 in fluorosilicone is also for sale . . . in packages of 100! I bought that, so have so many little blue O-rings I'll never use them all. If you want two little blue O-rings for free, send a stamped, self-addressed envelope to:

 

bumper (O-ring offer)

194 Taylor Creek Rd.

Gardnerville, NV 89460

 

Limited to stock on hand, all entries remain the property of Bumper LLC, decision of judges are final, we reserve the right to refuse service to anyone (or eveyone, for that matter), if you like your O-ring you can keep your O-ring.