912 exhaust connections

[Jerrytex]

Is is necessary to use the copper antiseize compound on the 4 slip joints on the 912 exhaust where the exhaust pipes slip into the muffler. I know I used it on the 582 exhaust but not sure if I need to do it on the 912 exhaust.

[Dorsal]

I believe the instructions specifically call for it.

[DesertFox6]

...AND...the day will come when you will be very glad you DID use it, Jerrytex; it's only a matter of time. It's cheap insurance against "Fox Bites" on your hands when you need to do anything with the exhaust system. I also have four Harleys to take care of, and the same is true in protecting against "Hawg Bites" :( from those critters too: Not to mention allowing your very expensive exhaust parts to "float" as vibration dictates without seizing and cracking as a friction-welded unit.

I'll back, and expand on, what Dorsal and DesertFox4 said: Always use anti-seize on your spark plugs and exhaust hook-ups; if it's good enough for mandatory military use in such cases, it's good enough for me! :)

"E.T."
(With scars to prove it! :D)

[Jerrytex]

Copper anti seize it is. Just on slip joints or on the down pipes where they go in to the heads too? Seems like it wouldn't cause any issues.

[Dave S]

Got a related question - I know of several mechanics who use aluminum/paste based anti-seize compound - particularly for spark plugs - but also on exhaust components.

What kind of luck have people had with this stuff in place of the copper anti seize compound?????

Sincerely,

Dave S

[DesertFox6]

I've always (30+ years) used the aluminum based product from Loctite Corp.; it's called Permatex Anti-Seize Compound. It's formulated particularly for aluminum block engines and related components. It's fantastic on cylinder lug bolts, spark plugs and exhaust slip-joints; anywhere it going to be HOT with the attendant expansion/contraction problems when the parts cool.

You can find it at almost any auto-parts store; a one ounce tube cost a few bucks and I think the one hanging over my work bench is at least 10 years old and still saving knuckles. It was just as fresh and spreadable as new when I put my 912's exhaust system back together last year following an overhaul, and felt just as new on some Hawg plugs I changed out last month. Like I said, cheap insurance!

"E.T."

[Jerrytex]

I have developed 2 cracks on the muffler in less than 100 hours! Not very happy right now. I used the copper anti-seize and I can't seem to get this (expletive) muffler off! Any tricks?

[jrevens]

Hi Jerry,

There are all kinds of things you can try. Gentle tapping with a plastic mallet, then application of heat around the perimeter of the outer tube... don't leave the heat (e.g.- propane torch) on too long. The idea is to expand the outer tube without too much heat soaking through to the inner tube. I've also had some success with Mouse Milk. You can get that from Aircraft Spruce. Let it soak in for awhile. Another thing to try- heating, then plunging into ice water will sometimes break it free.

When you reassemble, I've found that the very best anti-seize is the nickle-based stuff. It's silver colored like the aluminum-based, but has a much higher temperature rating - even higher than the copper stuff (I think around 2200 deg?) It's also very compatible with & recommended for stainless steel.

[Dave S]

John,

Haven't heard of the nickle based stuff till you mentioned it today....where does a person get it?

Dave S

[Jerrytex]

Well I got the exhaust off. Was not pretty. I freed one joint freed up but the other three stayed seized up until I bent everything up to get it off. Had to use an acetylene torch to get the three seized up joints apart. Needless to say, this is probably why the muffler cracked. A friend that has forgotten more about planes than I'll ever know is helping me now. He welded the cracks and we are sanding the joints to give them room to expand. Going back with a nickel base anti-seize. Thanks for the replies.

[jrevens]

Loctite is one brand, Dave. You can get it at W.W. Grainger's, some auto supply stores, on-line at ebay, etc. It's good for about 600 deg. higher than the copper-based products - actually about 2400 deg.

[Dave F]

>>Going back with a nickel base anti-seize. <<

That is the best stuff I use

[Jerrytex]

After going through this and royally screwing it up I suggest that anyone working on a 912 exhaust take the time, sand, align and use the nickel anti-seize. I had been smelling exhaust in the cockpit and thought it was just blowing up from the tailpipe but it was the cracks leaking. Caught them on the condition inspection. Now that I have it fixed, I can pull on the muffler and I can move the pipes in the collars and stretch the springs. Way better and hopefully no more cracks. Grainier supply sells the nickel anti-seize. Most auto stores can order it so you don't have to pay shipping.

[Peteohms]

Hi Jerry,

There are all kinds of things you can try. Gentle tapping with a plastic mallet, then application of heat around the perimeter of the outer tube... don't leave the heat (e.g.- propane torch) on too long. The idea is to expand the outer tube without too much heat soaking through to the inner tube. I've also had some success with Mouse Milk. You can get that from Aircraft Spruce. Let it soak in for awhile. Another thing to try- heating, then plunging into ice water...

I had occasion to look up this thread. Over the years I've had to remove my muffler and exhaust a few times. Had to remove head from #3 this week and the exhaust was stuck big time to the muffler. Thought I was safe because I always use anti seize. Well I pretty much used the above advice and other tricks. I finally made a concoction with 50-50 aircraft break fluid and soaked the joint several times and hung 150#s on the end of the muffler. I stopped and picked up some dry ice on the way to the airport to cold soak the exhaust while I planned to heat up the muffler at the connection. I had also made a tool to push the two apart and installed it Friday to leave the weekend for it to sit and absorbe the 50-50 brew. Turns out I didn't use the dry ice. I screwed my contraption a couple turns this morning and saw about 1/32" movement. I tapped on the joint with a plastic hammer and after a few taps, the 150#s pulled it apart.
The picture below was taken after I got the exhaust off #3. I just placed the tool on this exhaust to show how simple it is.

[Av8r3400]

Pete, that is absolute genius! Going to make one of those this weekend!

[Peteohms]

I don't show it in the photo but you'll need to put some shims between the tool and exhaust to keep some space to turn the nut.

[sourdostan]

Mouse Milk works wonders getting "stuck" exhaust parts apart. Available through Spruce.

Stan Specht
Denver, CO
Model IV Speedster
2390 hrs on 912ul

[Peteohms]

Used Mouse Milk, Moose Milk, Kroil, spray this, dribble that and nothing worked until two friends of mine, one of whom was a machinist, told me to use 5606 and acetone 50/50. Left it soaking for 2 days.

[fastfred]

This question is related to the exhaust connections. Does anyone wire the springs in place?

[jiott]

Yes, you safety wire the springs thru the center, not too tight because you want the springs to be able to flex. Then run a 1/4" bead of hi temp silicone along the length of the spring to damp out resonant vibrations.

[fastfred]

Thanks Jim. some guys do it and some do not?

[Dave S]

Fred,

The best explanation I heard on this procedure from an EAA tech counselor is that: 1) the loosely placed safety wire's purpose is to prevent broken spring parts from doing other mayhem should the spring come apart plus backing up the spring to keep the pipe together; and, 2) The silicon bead dampens vibration which could otherwise wear and elongate the holes and wear on the spring.

So it's real, real cheap insurance and yup - did it here too

[kmach]

The safety wire is very important on a pusher configuration, it keeps the larger broken spring part from going through the propeller.

I do mine on the Kitfox, it would keep a broken spring so you could inspect to see were it broke. I've never had one break though, I do change them if they get any groove wore in the hooks.

[fastfred]

Anyone ever have a spring break? Good insurance but they look similar to a snowmobile spring and I have never had one break in 30 years of riding them. They are expose to heat and rust.

[avidflyer]

I think they are far more likely to break on a pusher configuration where the little devils have the most chance of doing damage, especially if you didn't safety wire them. I've never had one break on me either, but have removed some that were quite worn, and if left to themselves would have eventually called it quits. I think the silicone will help keep them from vibrating and therefor have less wear. JImChuk

[jiott]

I have replaced several that were on the verge of breaking; and I have had the silicone on from day 1, now 660 hours.

[cap01]

i just had to remove the exhaust system to repair some cracks and a couple of the springs were worn so bad that there was so little metal left i could hardly see it, i don't know why they hadn't let go. they had almost 1100 hrs on them and had the hi temp silicone on them. when i installed the pipes i used silver anti seize

[fastfred]

I would probably plan on replacing the springs more often but still I have not heard of one breaking.1100 hours is pretty good on a $3 spring

[Russell320]

Well...it’s my turn. Cracks in the muffler found during condition inspection. So far, after two days trying, I’m unable to get the headers out of the muffler on my 912UL. I’ve tried all things discussed in this thread.....and they ain’t budging.

Any other ideas?......Thanks

[kmach]

I would first try a penetrating oil on the joints, let it soak.

if that didn't work , I would carefully heat the outer sleeve of the muffler that the header goes in.

Maybe some careful striking on the joint to release the sieze.

[Russell320]

Yep....tried all that. I knew this day would come and was hoping it would be later rather than sooner.:mad: As my dad use to say.....”suck it up and work the problem”. Sooo, that’s what I’ll do. Keep the suggestions coming!

[jrevens]

A lot of guys swear by Mouse Milk. I’m pretty sure it’s available from Aircraft Spruce and others. Might be worth a try.

[avidflyer]

I've heard that a 50/50 mix of acetone and ATF fluid is the best penetrating oil available. Maybe worth a try?? JImChuk

[jiott]

Have you tried an ice cold towel on the header pipe and some heat on the muffler port, along with the penetrating oil?

[Jerrytex]

Acetylene torch is the only thing I found that worked. Heats is quickly to red hot. Have someone on the pipe pulling/twisting as you heat the collar. Not a fun process at all.... alot of cussing.

I did find that I had to tweek and realign the collars to match back up to the pipes. When you go back together, sand the crap out of the collar and make it to where the pipes slide effortlessly in the collars. Use the Nickel anti seize. Anytime I have my cowling off, I grab the muffler and pull on it to make sure the joints still slip freely.

[Russell320]

Yep....tried all that too. Using Pete’s idea with a 3/8th nut,bolt and socket. Using mapp torch hasn’t worked, so acetylene is next. Thanks for your suggestions....keep em’ coming!

BTW...don’t expand too far with this setup....you’ll bend the tab into the header.

[avidflyer]

I can't imagine that the bolt as you show it between the spring tabs plus heat from a torch wouldn't work. Unless it somehow welded it's self together. (not likely) Show us pictures of your success! JImChuk

[Russell320]

Well....here it is...fresh off the airplane. What a pain that was. The cracks are from the two rear headers. Unfortunately, I don’t think I can save the muffler......a new one will be $795 from Kitfox and is custom made for your headers. It takes about 3 weeks. My guess is the cracks are from the slip joints not slipping. The muffler is from the early 90’s, so I’m not willing to fix it and then have it crack again from age. But......I may change my mind.

Mouse milk, mapp gas and a week of soaking finally did the trick. Did I mention it was a pain?

[Jerrytex]

Weld it up and keep the joints freed up. Heat the collars up red hot and woller them open a little. That will help in keeping them able to slip freely.

[Av8r3400]

Unfortunately that muffler has become so work hardened and fatigued, just welding the cracks will fail again very quickly. I added reinforcing plates on my last muffler over the cracks. That helped but also re-oriented the sleeves just enough that getting the pipes to line up was almost impossible. Then the stinger and blast tube failed rendering the muffler scrap.

The permanent fix would be to cut off the sleeves and replace them with ball joints.

[Dusty]

Out of interest, how many hours has this exhaust done?

[Russell320]

Mine had approximately 700 hours in service. One of the things that I think made it difficult to separate the header from the muffler is the use of Decalin RunUp. There was quite a bit of residue all over the internal parts of the exhaust system.......but it’s better than lead. And yes, I agree, there should be ball joints instead of slip joints.

The headers are now on the way to Kitfox to be matched with a new muffler.$$$$$$