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C180 Question: Monarch Fuel Caps.

I swapped out 2 on a customers airplane several years ago at oshkosh. I went by their booth and told them what was going on and they swapped them out, I got the impression they knew there was an issue. It looked like they did thread down far enough.

I have the original machined aluminum Monarch caps on my airplane and they have never leaked a drop since '90.
 
I still think its a combination of not enough vent pressure, & tank bladder collapsing and forcing gas out...

remember you can collapse an ALUMINUM cub tank just by vent hole being blocked in cap...(and it's not a pressurized system like yours)

is vent actually located that its pulling a vacuum? or blocked/flapper stuck??? someone build a nest in it??

if tank is staying inflated, there would only be air up by cap for it to suck out(except when full).... also is the act of fuel being sucked out collapsing bladder more??

I'd start with these steps
  1. check vent is open and flowing free by blowing in it with cap off
  2. remove filler neck plate and visually/physically inspect flapper
  3. reach in and check that ALL roof clips are in
  4. reinstall filler neck plate

if all that was good, relocate wing vent into air flow more to help keep bladder inflated

the fuel coming out of cap IS NOT the source of problem, it's the indicator of your other actual problem....
 
You are correct in that the bottom of the bladder is being drawn up. This is evidenced by the fact that the fuel gauge remains full. I have eagle fuel cells which are very thin and pliable so they lift easily. The fuel vent is open and only flows in as controlled by check valve. The flap under the cap works fine. I am convinced that when cap is not seated correctly low pressure on top of wing creates low pressure in tank drawing out fuel and collapsing the tank. If i pay very careful attention to seating the cap I have no problem. Installing the cap correctly is difficult because of the ratcheting mechanism in the cap and the way the o ring is designed. It is more apt to happen in winter when o ring is stiff.


Sent from my iPhone using Tapatalk
 
I still have the vent out the top of the cabin so there is no doubt that the tanks are vented and pressurized. I have an Eagle cell also. If it is a thread flaw like Wingwrench suggested, seems like a little measuring would figure that out.
 
180Marty said:
I still have the vent out the top of the cabin so there is no doubt that the tanks are vented and pressurized. I have an Eagle cell also. If it is a thread flaw like Wingwrench suggested, seems like a little measuring would figure that out.
Click to expand...


Increase pressure/volume then, by adding a bell mouth to vent pipe opening
 
180Marty said:
I still have the vent out the top of the cabin so there is no doubt that the tanks are vented and pressurized. I have an Eagle cell also. If it is a thread flaw like Wingwrench suggested, seems like a little measuring would figure that out.
Click to expand...

Also, if you have the single upper vent in wing root, is your problem with the tank on opposite side?? Liquid in low spot / blocking of crossover would be enough to cause gremlins
 
Also, if you have the single upper vent in wing root, is your problem
Click to expand...
Mike, my 1990 caps are working fine. Was just throwing that out since I don't really see how the vent is causing a cap problem.
 
I ran Monarch caps on a couple Cessna that came with the flush caps. Several thousand hours and no issues at all, except the flapper fell off one into the tank, so had to go on a fishing expedition.

I would NEVER consider going back to the original Cessna flush caps. A 185 on amphibious sat out in rain in Kodak for a number of days. Those tanks had so much water in them we drained them, cleaned, dried and started over. I had slumped, shook, slumped, taxied, drained, repeat multiple times and couldn't get all the water out.

Once water is in those tanks, it's REALLY difficult to get it all out......hence the "Killer caps" moniker, and the reason new Cessna have ~16 quick drains.

Texmex, you said your vents were completely out from behind the struts. You might want to check the service instructions on that as well.

MTV
 
180Marty said:
Mike, my 1990 caps are working fine. Was just throwing that out since I don't really see how the vent is causing a cap problem.
Click to expand...

because.... if you have adequate vent flow/volume, the tank issue will self correct itself once fuel is not near cap... path of least resistance, it would much prefer to suck air out... and would never be able to collapse(lift?) tank as fuel is withdrawn...

the cause of a problem is not always obvious or near the broken part.... your nose seal blows out & all your oil in the winter, not because it's a bad seal, but because your breather ices up at other end of engine......
 
180Marty said:
Did you see my request before to place the adapter plate and installed cap on a plastic glass filled with water and then invert to see if the cap leaks. Wouldn't be hard to do.
Click to expand...

I did that today, Marty-- held it inverted for about 60 seconds and it didn't leak a drop.
FWIW here's a couple of photos--
the first one shows how the cap stands proud of the adapter plate.
The other is a close-up of the cap seal.
It's not a standard o-ring BTW-- it has sort of a double-v profile.
I think that if someone's Monarch cap screws down flush to the adapter plate,
something is haywire with the seal.

monarch cap 1.JPG


monarch cap 2.JPG
 

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I have the monarch caps on my 73' 185 and had problems with them when I first bought it. It had been sitting 8 yrs. on a grass field untouched.when I first flew it on 15 min trip I lost several gals of fuel and blue stains out of the cap. The O-rings were dried out and monarch robbed me for two rings for like $40.00. And found the vent on the right side was plugged 2-3' in , lots of mud dauber sin the area. Cleared it with a wire. Check vent alignment and never had another problem or water. If you get them to work for you it's a good system. I think Mike is on the right tract, it's not likely the cap. BTW, the flappers in the filler neck on mine are bent back because the fuel nozzles with the ring on the end hang up and are captured by them. You have to put a thin screwdriver in to get the nozzle out.
 
I would like to "thank", or "Like" some of your guys/gals posts... but that function seems broken right now... I sent SJ an email.... just know we are reading them and trying to show our appreciation...
 
My caps are like yours Hotrod180. And the seals on the outboard are the same V profile.

Interestingly the inboards have an O profile ring. Why is it different?

I'm sorry, but one peice of the equation I should have mentioned, is when filling the first time on the outboard openings, I look across and see fuel pouring out the inboard caps, over the wing and onto the ground almost as quickly. Subsequently I taped up the inboards.

I was told by the previous owner that each wing had a single tank with two openings. I best scour the IPC and learn about this aeroplane.

I remember as a kid, the family sitting on the tarmac, as Dad took the 180 up for some ag-pilot type turns to get water out of the tanks. He had already drained a few buckets out. But that water came from a contaminated fuel drum.

Thanks everyone for your input.

Are the flush caps the same as the Bonanza's. And if so how do they get away with it?
 
texmex said:
My caps are like yours Hotrod180. And the seals on the outboard are the same V profile.

Interestingly the inboards have an O profile ring. Why is it different?

I'm sorry, but one peice of the equation I should have mentioned, is when filling the first time on the outboard openings, I look across and see fuel pouring out the inboard caps, over the wing and onto the ground almost as quickly. Subsequently I taped up the inboards.

I was told by the previous owner that each wing had a single tank with two openings. I best scour the IPC and learn about this aeroplane.
Click to expand...
Your airplane has a seaplane kit with long range fuel tanks. The long range tanks have two fillers for convenience of fueling when on floats. They will hold a little bit more when filled at the outboard fillers.
Try swapping the inboard caps with the outboard caps to determine if the "V" profile seal will also leak or not. Your "O" rings are likely just old and stiff. I don't know about Austrailia, but here near a big city I can get "buna-N "O" rings from a local bearing shop for a reasonable non-airplane price. They are identical to the airplane variety.
 
texmex said:
... the seals on the outboard are the same V profile. Interestingly the inboards have an O profile ring. Why is it different? I'm sorry, but one peice of the equation I should have mentioned, is when filling the first time on the outboard openings, I look across and see fuel pouring out the inboard caps, over the wing and onto the ground almost as quickly. ...
Click to expand...

I wonder if someone in the past has switched out the seals on your inboard caps from the doube-v rings to something else?
Hae you tried replacing them with the correct part from Monarch (not a standard o-ring)?
 
I have Monarch aux tanks in my 185 with Monarch caps and have had no issues.
My caps are more like conventional caps not the screw on ones.
Not sure when they changed.
IMG_0138.jpgIMG_0139.jpg
 

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I believe those are Monarch replacement TANKS, correct, Tom?
Click to expand...
I always thought the fiberglass replacements for the main tanks such as my slant ones used the same plate and cap as I'm using with my bladders. Thinking that cap goes on the 15 gallon tank that can be installed outboard of the originals. Wish I stlll had my brochure from Bill Barton.
 
Found this on Hartwig's website. Must be the original install instructions. Notice plate fits bladder or plastic tank.
Screenshot_20170130_084037.png
 

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I have flint internal tanks and the filler neck is under a sheet metal door right next to the wing tip. If the cover was removed the cap in the pic would fit.
 
algonquin said:
I have flint internal tanks and the filler neck is under a sheet metal door right next to the wing tip. If the cover was removed the cap in the pic would fit.
Click to expand...
Except that the diameter might be a bit tight in the well and the Flints do not have a vented cap.
 
The conventional style likely works better because there is no ratchet mechanism. Unless I very deliberately position the cap as I install it, it will ratchet before the o ring is properly seated. If not seated it leaks....alot. Replacing the $55...yes $55 o-rings often and keeping a bit of o-ring lube on them helps.


Sent from my iPhone using Tapatalk
 
Unless I very deliberately position the cap as I install it, it will ratchet before the o ring is properly seated. If not seated it leaks....alot. Replacing the $55...yes $55 o-rings often and keeping a bit of o-ring lube on them helps.
Click to expand...
Interesting, I have never had the cap cross threaded like that to where it ratchets prematurely. My caps are at least 26 years old and I've never replaced the rubber seal or put any kind of lubricant on.
 
Skywagons 8a right, sorry was referring to the two tabs not the screw in type on the reg monarch. Wouldn't go down in the recess.
 
180Marty said:
Interesting, I have never had the cap cross threaded like that to where it ratchets prematurely. My caps are at least 26 years old and I've never replaced the rubber seal or put any kind of lubricant on.
Click to expand...

Same here, just looked up my paperwork, bought the tanks and caps in 1988 and seals still look new.
 
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