Mysterious blue residue? Exhaust leak?

Hi Nick

Roger and Sean are 100% correct.  Also I would not fly it with an exhaust leak personally.  

Is this a factory exhaust system or the cut and weld version by the OEM?  Rotax usually supplies just the bends, straight pipes and the muffler with the sockets installed.  Generally the issue is the alignment was perhaps not done correctly by whomever cut and welded it together.  If the socket joints are at extreme angles you may have to have it cut and repaired to correct that.  Rotax does sell spares for the system if you have a cut and weld version.  Some OEM only use the Rotax canister and make their own pipes to mate up.  Knowing that might help if the alignment suggestions don't help. The socket joints are needed to absorb the high frequency vibrations that occur so the pipes do not crack. 

Check the installation manual as it has all the correct material to fit an exhaust.  See if your sockets match what they show and it also has the information on the exact material that the exhaust parts (the ones from Rotax) are made from so you can weld them correctly. 

Just a tip, Loctite anti seize comes in different temperatures.  Get the one that has nickel as the metal in it.  The reason is it has a higher rating that the other versions.  

Cheers

Nickel anti-seize on exhaust pipes.

Nick wrote:

So is it possible to eliminate these leaks? Or are small leaks just part of the game with Rotax? The design is pretty poor. I was using exhaust heat wrap before and I think it was hiding some of these leaks. 

Is there any type of sealant that can close the gaps in the exhaust ball joints.

I’ll give it a go trying to adjust everything. 

should I adjust all of the pipes or just the main one that’s causing the problem?

airplane was supposed to go to annual this week. No way I’m flying it like this.

Video of leak

I have had two Rotax 912ULS powered aircraft -

The only exhaust leak I have had was on the first, at about 800 hrs plus, the muffler developed a hairline crack in one end.

My uninformed guess is that the crack was brought on by fatigue, possibly due to the unsupported tail pipe that exits from this side.

The replacement muffler and my latest 912 have the tail pipe supported by a lightweight spring, in the hope of delaying any fatigue related cracking.