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  #91  
Old 10-29-2014, 11:54 AM
Smilin' Jack Smilin' Jack is offline
 
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Great write up Karl,
You did a great job. Emergencies usually take us all by surprise. You can practice and practice but when it happens all that training goes into dead cells for awhile until you get your cool back.

Prop seal.... leaking yes but blowing out Wow you did a great job. I guess that nearest airport feature is a great feature.

Smilin' Jack
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  #92  
Old 10-29-2014, 12:44 PM
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PerfTech PerfTech is offline
 
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... I have started a new thread in this discussions area addressing this titled;ASA Vacuum System Concerns. I started a new one so it doesn't get lost in a large discussion. This should be considered a
SERVICE BULLETIN
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Last edited by Mike S : 10-29-2014 at 01:00 PM. Reason: Added link to new thread
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  #93  
Old 10-29-2014, 01:09 PM
OKAV8r OKAV8r is offline
 
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Location: Edmond, OK
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Quote:
Originally Posted by Gash View Post
...One thing I think is being glossed over here is the reliability of the NAPA 2-29000 check valve. As far as I can tell, this item is quite reliable. It's been around since the 1970s (or earlier?) and would qualify as "proven" technology...
I wouldn't put a great deal of stock in the proven reliability of that valve, unless it is known that the quality of manufacture hasn't changed over the years.
FWIW, NAPA is now a Chinese company
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  #94  
Old 10-29-2014, 01:50 PM
Jeff Hagg Jeff Hagg is offline
 
Join Date: Mar 2011
Location: Indpls. IN
Posts: 35
Cool Check for crankcase blockage

Ice can form around your crankcase tube and block this passage. Things will start to freeze up this time of the year. Pilots beware! Blew the crankcase seal on my Starduster II this way.
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  #95  
Old 10-29-2014, 03:41 PM
jrs14855 jrs14855 is offline
 
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Location: Lake Havasu City AZ
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Default Vent tube

Quote:
Originally Posted by Jeff Hagg View Post
Ice can form around your crankcase tube and block this passage. Things will start to freeze up this time of the year. Pilots beware! Blew the crankcase seal on my Starduster II this way.
This is a problem that dates back to at least the mid 60's and in many cases has nothing to do with a check valve.
Around 1964 Piper started slotting the aluminum tube near the top to provide relief if the lower end of the tube froze up. At the time no one understood what the slot was for. On the Pitts as well as most aerobatic aircraft with a Christen type inverted oil system, it is normal to run the vent tube all the way back to the tail. Pitts provides an alternate tube for cold weather operation that vents to the bottom of the firewall. I flew my Pitts a few times in freezing temperatures with the tail outlet, never had a problem.
The vast majority of the posts on this subject ignore the fact that the Lycoming nose seals blow out for a variety of reasons, many of which have nothing to do with the check valve. Improper installation of the seal its probably a much greater problem than clogged check valves.
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  #96  
Old 10-30-2014, 01:13 AM
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rvmills rvmills is offline
 
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OK, no flame intended here at all?just more discussion

Honestly, in one sense, ice blocking a non-whistle-slotted breather, or an improperly installed nose seal, as causes of seal blowouts, while certainly possibilities, are a bit like distractors to the coked-up CVV stem discussion?yet they both add value to the discussion. That may sound like playing to both sides of the aisle, but its not?

Sure, they could each cause a blowout, but I've not heard anything from Gash to indicate he suspected the latter, and the former is a non-player in his system set-up.

Talking about the ice build-up is a good reminder to those with standard breather tubes?something to check as we head into winter (cleanliness, mounting, whistle-slot integrity.

Crank-seal installation?Gash, I have some gouge for ya, if you do this yourself.

But the CVV stem coking needs to remain the focus, so folks can be eyes-open on the issue. I say this, and I do still have mine installed?with open eyes.

My discussion here is about my experience, and may or may not be related to Gash's experience. I had what sounds like a similar level of blockage in a much shorter time...about 4 months and 70 hours (slower winter months). My engine is a 540, though not in a 10. My CVV was also broken inside. I did not have a seal blow out, and initially wondered if Gash's being coked up, down to a 1/8" hole, could cause a seal blowout. Not questioning his diagnosis, I say this as a rhetorical question of "what size hole causes a seal to blow?" There's probably a lot of "it depends" in there, and seal installation quality likely is a "depends" factor. Another interesting finding has been that since that time, I've inspected at oil changes and during other cowl-off maintenance, and have not seen anywhere near that speed or severity of coking. Very minor build-ups near the weld on my DIY saddle. Not sure why, and I don't know if coking starts slow, then accelerates as the clog gets large, but I have seen only very insignificant deposits since that first major clog. Since my clog occurred in winter, I will be watching closely this winter as well, to see if it gets worse again?just for a data point. No idea if cold weather has any significance at all though?just data seeking.

In my case I did chase leaks, and changed the nose seal twice?once before the AOS/CVV was installed, and once after. The seal leak was worse on the first swap, in which I replaced a split seal with a split seal. I felt I was diligent in the first installation (my knuckles bore the brunt of my diligent cleaning of the crank bore!). It held for a while, but began to leak again, though not as badly. During that time, I did install the AOS and CVV. My impression was that my oil leaks did seem to increase slightly after the install, but can't say how long after?very non-scientific swag.

Did the nose seal start to leak again due to the coking, I dunno?certainly possible. I do know that I got some additional advice from Lycon on the second seal swap; used a one piece seal, did a better job of sanding a helical pattern in the bore, and used Lycon's recommended Scotch Weld 1300 glue, versus Ace-bought Pliobond, on the second go-round (and my knuckles were even worse off). So I can't point to the CVV as the only culprit, and I don't think my head is in the sand. I also changed two prop governor gaskets, one oil return line, and chased and chased this, both before and after the CVV was installed. Even found a cracked (and poorly repaired) old oil breather adapter fitting.

After I found the coked stem, I went to a regular inspection interval, as described above. Still had some pesky oil leaks though, and replaced an oil cooler line, then the oil cooler, which had developed an internal leak (with a consistently clean CVV stem).

The last 10 hours have shown the cleanest cowl innards I've had for a while, but that is a very short sample size. Still watching closely, keeping the valve/stem clean, and have the 2 NAPA valves installed. I would like to test for the vent vacuum amount being provided, and will do so to add to this discussion. The clean belly concept has never been a big factor for me in this, though cleaning only smoke oil residue off the tail would be kinda nice! And if there is no vacuum, I'll work with Allan to see why, and see if it can be improved. I'll provide him candid feedback, good or "other", and post here too.

Cheers,
Bob
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  #97  
Old 10-30-2014, 08:52 AM
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Mike S Mike S is offline
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Quote:
Originally Posted by rvmills View Post
But the CVV stem coking needs to remain the focus, so folks can be eyes-open on the issue.
Eye on the prize-----thanks for keeping things on track

Quote:
Originally Posted by rvmills View Post
I did not have a seal blow out, and initially wondered if Gash's being coked up, down to a 1/8" hole, could cause a seal blowout. Not questioning his diagnosis, I say this as a rhetorical question of "what size hole causes a seal to blow?" There's probably a lot of "it depends" in there,
Thinking about this, the coke buildup itself may well be a limiting factor----------it takes some oil to be baked into the coke, right??

As the hole closes up from the coke, what happens to the available vacuum, and the flow of oil???

I wonder if there is a spot where the buildup will limit the oil flow to where there will be no more buildup----------yet there will still be a small opening???

Can the coke actually close off the hole entirely ????

Now back to your regular programing.
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  #98  
Old 10-30-2014, 10:12 AM
nodgnal51 nodgnal51 is offline
 
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Default Clean the belly

I couldn't agree more with Pierre, I'll keep the vent tube open and clean the belly. Better to clean the belly than lose the plane.
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  #99  
Old 10-30-2014, 01:39 PM
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DanH DanH is offline
 
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Reality says the informed will make their own choice.

The real issue involves getting the word out about coking the exhaust tap, so the uninformed will not descend from the heavens in a shower of oil.
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  #100  
Old 10-30-2014, 02:14 PM
BillL BillL is offline
 
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Quote:
Originally Posted by rvmills View Post
OK, m . . . "what size hole causes a seal to blow?" There's probably a lot of "it depends" in there . . .

Cheers,
Bob
Really good question! It also probably depends on how much blow by there is. Also, as rings rotate etc, does the blow-by change, wander with time? Probably.

Bob, As you check the crankcase pressure would it be possible to install an orifice of a couple of sizes to see how the pressure changes? I bet that is already in your test plan

I gotta get finished and flying so I can provide some data too.
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