912 exhaust connections

[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.

[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.

[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.

[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