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C180 Question: Monarch Fuel Caps.

texmex

MEMBER
Hanging Rock, Australia.
My C180J came with Monarch fuel caps. And after losing several hundred dollars of fuel out of them I'm changing back to the originals. Fortunately the previous owners still has them in a box.

I've ordered four new cork gaskets and hardware. I've also got two blanks for the inboard filler holes in the long range tanks. And obviously I'll service the old caps.

Is there anything else I need to know? I'm hoping the STC instructions are in the logs and I'll just reverse the process. The previous owner mentioned something about the fuel tank vents. Are they changed with the Monarch caps?

Many thanks,
Denis.
 
I have monarch caps on my 180k had leaks I fought for a while it was main screws on tank lids. Vent system is the same. Have them for 15 years. Have seen them on a 185 with vent tube way out of adjustment and not leaking.my system has slight pressure in tank when I go to l cap as soon as l land. You can check check valve by putting a hose on one of the vent tubes and blowing in to the tank. I feel it pressure up then valve slowly release the pressure.all normal.my main screws needed re torquing .
 
Should be a simple change back. Shouldn't have to do anything with the vents. Interesting how some seem to have bad luck with Monarchs and I've had a great experience since installing in about 1990. I did buy mine from Bill Barton who invented them. Here is a picture of mine----does your cap look different?That rubber gasket seats snug when closed.20170126_131102.jpg20170126_131216.jpg
 

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If you need my address to send your old monarch caps I could use a couple spares let me know.

thanks in advance
 
Thanks guys.
180Marty - Similar, but stainless. The top looks the same but the gold flat underneath a little different from memory. Interestingly the outer ones have a V rubber ring and the inners an 'O' ring. Most leakage out of the inners.

Mike - Short answer yes. But thanks for the AD alert. I'll look that up. I had Atlee Dodge caps on the Cub so I'll also look that way. Thanks.

Piper J5.5 - They'll be all yours.

My aircraft lives in a hangar and I have no problems with servicing the flush caps every couple of years.
 
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Mike - Short answer yes. But thanks for the AD alert. I'll look that up. I had Atlee Dodge caps on the Cub so I'll also look that way. Thanks...

please DO NOT reinstall the flush caps... they were not called "the KILLER Cessna gas caps" for nothing

I think looking into PROPER vent location(by strut) will help you fix your issue as others have mentioned...

I think you are blaming the wrong part for the ROOT of your system's problem...
 
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What are the Killer Caps? I have a low time 2100TT, '58 C172 I bought last year that was complete but it sat untouched in a hanger for 12 years, annual completed in 2004 and than the owner never flew it again after putting it in the hangar. He was in his 80s

We pulled the cylinders off and inspected for corrosion and got it back together and almost ready to see if the o300 will make some noise. It has red gas caps I believe, are these the Killer Caps?
 
What are the Killer Caps? I have a low time 2100TT, '58 C172 I bought last year that was complete but it sat untouched in a hanger for 12 years, annual completed in 2004 and than the owner never flew it again after putting it in the hangar. He was in his 80s

We pulled the cylinders off and inspected for corrosion and got it back together and almost ready to see if the o300 will make some noise. It has red gas caps I believe, are these the Killer Caps?

flush caps that collected & let water in....

yes they were red?? i think???

been removing them since I started in late 1980's

but i think Cesnna also made a replacement tank filler that had raised caps that were also red???
 
Thanks, I found this picture, mine our not the ones shown as killer in this pic, I think I have the raised cap in the middle, going to check today.

_20170128_013234.JPG
 

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another thing that bothers me on this/makes me scratch my head.... (BCP site videos)

HOW can there STILL be fuel up against CAP after 1 hour flight, as described in comments on video...

I suspect someone with short arms(like me) was unable to reinstall(improper work) all the upper bladder clips to roof of tank bay, and bladder is collapsing as fuel is drained???
 
My C180J came with Monarch fuel caps. And after losing several hundred dollars of fuel out of them I'm changing back to the originals. Fortunately the previous owners still has them in a box.

I've ordered four new cork gaskets and hardware. I've also got two blanks for the inboard filler holes in the long range tanks. And obviously I'll service the old caps.

Is there anything else I need to know? I'm hoping the STC instructions are in the logs and I'll just reverse the process. The previous owner mentioned something about the fuel tank vents. Are they changed with the Monarch caps?

Many thanks,
Denis.

after thinking on this... caps are NOT your issue here.... thinking lack of clips/not installed well & holding bladder up to tank bay roof, as mentioned above

most gas Caps on airplanes in general, just have a blank hole drilled in them under top, not even a oneway valve (that only allows flow into tank, not out)

thoughts?
 
#1 (i admit if plum full, there could be gas next to cap, and somehow get sucked out)

but once fuel is used some, it should just be just air up top by gas cap, and air being replenished by vent by strut... no way tiny leak in cap could cause the gas flow shown in the videos at other site..... unless top bladder clips are not still holding bladder up??.....
 
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What really puzzled me was that I taped up the inboard caps.IMG_2480.JPG

Now admittedly it was not fuel proof tape. Just that threaded general tape. But I thought if I stopped the venturi effect around the caps it wouldn't pull the fuel out. But some how the fuel ate the tape where it curves up over the cap and sucked the fuel out. With the extra downward pressure of the tape on the o-ring, and no venturi effect, fuel still sloshed out to eat the tape. That really peeved me. I think I should have removed the caps and found some aluminium tape.

There's about 3 hours fuel per side but the tank was dry after only an hour of flying. In my country and dollars, that's about $200 per side. Ouch!! All behind the tank and all over both tailplanes was blue fuel stains. As I said above the inboards were by far the worst with only a few little marks from the outboards with the rubber 'V' rings. Why would the inboard and outboard rubber ring seals be of a different profile?

The fuel vent is fully forward and fully exposed to the airflow but I think I saw on the Monarch web site that the vent should be mostly behind the wing strut. Could it be over pressurising?

Mike, I've always appreciated your input over the years, and I acknowledge your concern. As an aside if I blank off the inboard holes does the cork gasket go on dry?

I've put in a few Bonanza bladders before but never Cessna. Are there similar clips holding the bladder up? I'll look at the IPC.

Hotrod180 - thanks for the link. When I finish work tomorrow I'll look at it with interest.

Thanks all.
Denis.
 

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Very interesting. Would be interesting if the cap was totally removed and then tape over the ~2 inch opening that the cap screws into. The flapper deal down in a little should seal things to begin with.
 
I installed a Cessna service kit with the new style caps, similar to the raised caps in the center. No more problems with leaks, water, etc.
 
I started a thread about Monarch caps on the BCP site recently....

I'd been thinking lately about installing the Monarch caps that came with my airplane when I bought it a few years ago.
After reading all the pro & con comments on Monarchs,
I decided to just fix the screwed up latches on the stock fuel filler covers (aka "flapjacks") instead.
FWIW they're Hartwell #5000-2 latches, available from Wicks for about $22 a pop,
but a buddy of mine had a couple he picked up at a fly market somewhere.
I'll keep the Monarchs on the shelf, if & when I have bladder issues maybe I'll install them then.
 
I have Cessna service kit elevated caps inboard and flush caps outboard. Never any water problems but I almost never use the outbaords so the O rings don't get any wear. Flush caps are too inconvenient for everyday use and that's reason enough to change them.

My Backcountry kit came with flush fillers and caps. Atlee's made me riser necks and caps very early in the project.
 
I'd been thinking lately about installing the Monarch caps
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.
 
I would top the tank off and find a fancy turbocharched injected leaf blower and point it at the gas cap and see if you can pick up some more clues
 
I have these caps on my 180 and have spent many hours setting up the vent as described in the instructions and as directed by Hartwig. If I don't personally install the caps to make sure they are seated and keep the $55 seals lubricated I WILL loose fuel. As much as 10 gallons in an hour. I would not recommend these caps to anyone.


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I have had ZERO issues with Monarch caps and have installed many sets. It is usually top of the list of mods for an early Cessna.

The old original Cessna recessed adapters with well and lid are HORIBBLE! I have seen them full of water and also frozen water.

I would love to know why some guys are having issues with Monarchs. It seems pretty simply designed
 
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