If anyone is thinking of installing these caps, I just want to add my experience here regarding these caps.
I have a C185 with long range tanks and 2 caps per wing.
My Monarch caps leak horribly. I have had numerous conversations with Hartwig who sells these. First they blamed it on incorrect placements of my fuel vents causing overpressures, vacuums, etc in my tanks. I spent hours referring to the Cessna Pilot Association adjustment procedure for these to no avail. Then Hartwig very graciously sent me 4 new rubber cap gaskets...no change.
I have fuel venting out of all 4 caps when my tanks are topped off to the point they have permanently stained my brand new paint job and ruined the paint on top of my wings. Even worse is I never know how much fuel has been getting sucked past these caps. I flew home to Colorado from Alaska last Fall and feel very fortunate I did not run out of fuel inadvertently over some remote stretch in the sketchy weather I had!
These caps are TERRIBLE and if you are thinking of getting them please think twice... The raised Cessna caps are a proven design so if you have them I would not change them. Yes the Monarch caps look "cool" but beware!
If you are contemplating these please contact me and I'd be happy to send you a graphic photo of the leaking caps!
I am currently shopping for surplus Cessna cap assemblies and will be replacing my Monarchs asap, so if anyone has a set of the raised Cessna cap assemblies they'd like to part please let me know...

redhawk wrote:If anyone is thinking of installing these caps, I just want to add my experience here regarding these caps.
I have a C185 with long range tanks and 2 caps per wing.
My Monarch caps leak horribly. I have had numerous conversations with Hartwig who sells these. First they blamed it on incorrect placements of my fuel vents causing overpressures, vacuums, etc in my tanks. I spent hours referring to the Cessna Pilot Association adjustment procedure for these to no avail. Then Hartwig very graciously sent me 4 new rubber cap gaskets...no change.
I have fuel venting out of all 4 caps when my tanks are topped off to the point they have permanently stained my brand new paint job and ruined the paint on top of my wings. Even worse is I never know how much fuel has been getting sucked past these caps. I flew home to Colorado from Alaska last Fall and feel very fortunate I did not run out of fuel inadvertently over some remote stretch in the sketchy weather I had!
These caps are TERRIBLE and if you are thinking of getting them please think twice... The raised Cessna caps are a proven design so if you have them I would not change them. Yes the Monarch caps look "cool" but beware!
If you are contemplating these please contact me and I'd be happy to send you a graphic photo of the leaking caps!
I am currently shopping for surplus Cessna cap assemblies and will be replacing my Monarchs asap, so if anyone has a set of the raised Cessna cap assemblies they'd like to part please let me know...

This is upsetting news, I know how frustrating it can be when a mechanical system is not performing as it should. However, I can offer direct observed and anecdotal evidence that these caps work exactly as advertised with zero problems on at least 10 airframes here in the seattle area, including my own Cessna 182.

I personally installed Monarch cap assemblies on Kenmore Air Harbor's two 1978 Cessna 180s with extended fuel back in 2003-4. Since then these 2 airplanes have been parked outside in rainy Seattle next door to a concrete plant and operated for an average of 500-600 hours a year flying. There's never been a single report from pilots or linecrew about leaking fuel past the caps. In my opinion these caps are not terrible but in fact wonderful!

I've spent the majority of my adult life working on machines, mostly airplanes. We once spent 3 years trying to find the source of a loud noise in a turbine otter that occurred every time power was reduced past a certain value in flight, what a pain in the ass! There was quite a party when we finally figured it out. Sometimes you just have to stick to the troubleshooting for way longer than what seems reasonable.

At the risk of sounding like yet another Internet know-it-all I will submit that there must be something in your installation that is not right, there is simply no way for fuel to leak past the thermos bottle threads and o-rings on these caps if they're installed properly, it's physics. I'll start believing in Santa Claus again before I believe in fuel seeping past a fuel proof seal.

I will agree that if you have the raised Cessna caps that there's very little need to change to Monarchs, especially with the higher price they're getting for Monarchs these days. It would mostly be a cosmetic improvement.

I have no connection with Hartwig other than years of good service as a customer.

Great post Halestorm, just yesterday I filled my right tank so full that the little Monarch flapper still had a little fuel on top when it was closed. I went flying and no fuel spewed out the top past the cap. There is a good post over on Supercub that shows a mechanic's mistake is the problem and not the part. It's by JohnnyR towards the end of Cessna 180 Fuel Vent Issue thread.

I've spent the majority of my adult life working on machines, mostly airplanes. We once spent 3 years trying to find the source of a loud noise in a turbine otter that occured every time power was reduced past a certain value in flight, what a pain in the ass!

That sounds like a story that I'd like to here----Please.

Redhawk, I'd sure encourage you to make the effort to resolve the problem, rather than just change out the caps. You may very well have other issues with your fuel system venting and check valves. As these birds age, some of the components need to be changed to renew them to full operational capability. The Monarch caps are well proven throughout the fleet. The Monach caps have been on my airplane for many years and don't leak.

180Marty wrote:

I've spent the majority of my adult life working on machines, mostly airplanes. We once spent 3 years trying to find the source of a loud noise in a turbine otter that occured every time power was reduced past a certain value in flight, what a pain in the ass!

That sounds like a story that I'd like to here----Please.

Had to do with the way the engine mounted fire-shields rubbed on the containment ring, when power was reduced with less air going through the compressor the excess ram air would vibrate the shields like a saxophone reed.

We kinda knew what it was for a while before we homed in on the exact location of the noise, it was mostly an annoyance and not an airworthiness situation, part of the reason it took so long to figure out.

On another forum for Cessnas, in the 182 section, there was a post where several others were having issues with the Monarch fuel caps. There was even a post where the monarch guys travel with extra seals because of problems.

I have had a similar disappointing experience w/ Monarch Fuel Caps (1959 C-182B). My right cap sits higher and not as tight as the left side (although there is no adjustment). I am going to be at the Alaska Air show this weekend and I will be bringing photos to show the rep. I have contacted the company in the past and have had little positive response. They sent me a new cap to try but no change.

Dave

Hartwig is sending me 4 new caps... will see if this solves the problem, but I'm a bit skeptical...
Kudos to Hartwig for working with me on this!
Please keep any similar experiences coming. I appreciate all the posts!

I hope the new caps they send resolve your issue..... but it's highly unlikely
The fresh rubber seals will work for a while but they will eventually leak (unless the caps have recently been redesigned). Makes me laugh when monarch cap owners borderline get offended when they hear something negative about them, lol. Sucks you don't have your old cap assemblies, that's probably the only guaranteed fix.

Hartwig is sending me 4 new caps... will see if this solves the problem, but I'm a bit skeptical...
Kudos to Hartwig for working with me on this!

Pull a plate that the cap screws into off and do the inverted water test I asked Hotrod to do with his.

The fresh rubber seals will work for a while but they will eventually leak

Meanwhile, the rubber seal on mine that is 27 years old is still sealing---it is in the hangar most of the time though.

This thread makes me think of E10 ethanol fuel vs E0 that some people will drive many miles and pay big bucks. Just yesterday, I mowed the grass with a 20 some year old Lawnboy that had E10 2 cycle oil mix that was put in the jug last Sept. It started on the third pull. I'm betting that you guys wouldn't have the same experience---just the way it is I guess.

180Marty wrote:...Pull a plate that the cap screws into off and do the inverted water test I asked Hotrod to do with his.....

Can't find the thread, but I did test mine and report on it.
Cap holds water fine when inverted, flapper did not.

7years, 1000+ hours with Monarchs on my 1954 180. No problems

You don't have to run these caps for a 1000 hours to know they suck. Whatever. Buy them, they look so cool.

180Marty wrote:This thread makes me think of E10 ethanol fuel vs E0 that some people will drive many miles and pay big bucks. Just yesterday, I mowed the grass with a 20 some year old Lawnboy that had E10 2 cycle oil mix that was put in the jug last Sept. It started on the third pull. I'm betting that you guys wouldn't have the same experience---just the way it is I guess.

2-stroke oil works as a fuel stabilizer and helps prevent the issues that ethanol in gas causes. I just had to get my Valkyrie carbs rebuilt ($~900!!) because I let it sit with ethanol gas in it. Learned that lesson. My generator still has some Alaska gas (E-0, and 4 years old) in it with fuel stabilizer - starts right up every time.

Seems like Monarch caps are like wheel landings- people either love them or hate them.
If anyone wants to risk death & destruction, I've got a set for sale on the marketplace forum.

Good posts, I have Monarch aux tanks on my 195 with the OLD style Monarch caps and they do not leak a bit. The old style caps look like the new ones from the outside but use a conventional twist lock system. Talked with Hartwig at SnF this year and he just shool his head when I asked about the different caps.

Tom

A solution I've thought of is to plug my inboard fuel ports, and return to the original non-float configuration of just the outboard caps.
If anyone has the parts and pieces from converting to the 2 cap per wing setup and want to part with them please let me know, or if anyone knows where to find these it would be much appreciated!
Thanks

I have a 180k wet wing and I have been having the same issue with the Monarch (new Install). Tons of time spent with the CPA bulletin. Phone calls to the MFG. New seals given to me at Sun n Fun. Blue wings, $$$$$ lost over the wing. Short hops taking on a lots of fuel.

I had one cap leaking. I could move the cap and the leak would follow the cap. Monarch sent me a new cap. I put it on the right wing where the leaky one was. Now the other one is leaking. I will call them again today. I just wonder if it was a bad lot of the newer caps. Mine seem like the detent click real easy. I agree with the guys that have an older set. I would like to find a old set of caps to try. Now way they built the great reputation they have with these problems.

This is getting real OLD FAST. I will have to get new tanks adapters to go back to Cessna flush or take a look at the Dodge flanges that use the Cessna raised caps. If this can't be trusted.
John

Bearhawk_Cub wrote:....or take a look at the Dodge flanges that use the Cessna raised caps. ...

Those are kinda spendy, they cost almost as much as a set of Monarchs.
But they're an ingenious solution to the "killer caps" problem.
My hat's off to whoever designed them.