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robthart

Exhaust issues with Rotax

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Have now had two exhaust breaks on 2008 CTLS within a 4 year period; one on either side of the engine! Each occurred during descent to land phase while approaching airports, and each appears to be in similar locations with relation to the pipe... is this a recurring problem and/or a 'known' issue with Rotax?

 

Nov 2018.jpg

Dec 20014 (1).jpg

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This is the most common area. What causes this is usually the muffler has been put in a stressed position and then vibration that may be caused by a prop that needs balancing, not keeping the carbs synced and or old engine mounts. These can be welded and have them add a small 2" long by 9/16" wide strap downward across the new weld. It will be good as new. Make sure that when the muffler goes back on the knuckles where the exhaust pipes join together are lubed with nickle anti-seize.  Make sure the exhaust pipes slip into the knuckle without lateral force and maybe get the prop balanced. If you are past the Rotax 5 year rubber time did the mechanic change the engine mounts? If not do this.

 

If you search the forum here you can find a couple of pics when Andy had a break at the same spot here in Tucson and how it was fixed.

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2 hours ago, robthart said:

Have now had two exhaust breaks on 2008 CTLS within a 4 year period; one on either side of the engine! Each occurred during descent to land phase while approaching airports, and each appears to be in similar locations with relation to the pipe... is this a recurring problem and/or a 'known' issue with Rotax?

Dec 20014 (1).jpg

Looks familiar, that;s exactly where mine broke.  Bad welds seem to be the culprit.  I wonder if the exhaust "shock cools" when going from cruise power/temps to a descent with reduced power...?

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Roger is right on the repair.  Here's my crack and repair, way stronger than it needs to be:

12034197_10153618820208286_4224634514668

12039039_10153619519473286_1457858065788

12028681_10153619519218286_4415464144481

 

You can see I also had a plate welded on the end of the muffler; I was having spiderweb cracks from the welds around the exhaust pipe too.  These repairs have held up great for 3+ years, I expect them to outlast the airframe.

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Our mechanic suggested replacement as opposed to repair on this one, would have to send off to MSP for a certified weld & would hate to learn they can't do... know what the 'ballpark' figure is for new pipe vs certified weld? (I'm sure labor would be the same either way).

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Good looking repair Andy.  Those pipes will still be functional after the CT is gone!  Bad area to have this break.  It's near the battery, regulator & solenoid.

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40 minutes ago, robthart said:

Our mechanic suggested replacement as opposed to repair on this one, would have to send off to MSP for a certified weld & would hate to learn they can't do... know what the 'ballpark' figure is for new pipe vs certified weld? (I'm sure labor would be the same either way).

Hold on.

Recommend you send it to Tucson. Roger has a guy there that does stellar work on those pipes and also muffler, if applicable.

Andy’s repairs were done by him. I cannot find his card, but Roger can put you in touch with him.

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That does look like good work Roger & Andy, if someone can pass the info on the weld wizard I'll get it to our mechanic, thx!

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15 minutes ago, WmInce said:

Hold on.

Recommend you send it to Tucson. Roger has a guy there that does stellar work on those pipes and also muffler, if applicable.

Andy’s repairs were done by him. I cannot find his card, but Roger can put you in touch with him.

Yeah, if I ever need welds done on my exhaust again, I'll send it back to that guy.  Really top notch.  He did all that stainless work for me in a few hours and only charged me (IIRC) $185.  I was 1500 miles from home and needed to get in the air to get home; he could have charged me anything he wanted and I'd have had to pay it.  

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1 hour ago, robthart said:

Andy can you send me his contact info pls, thx!

I don't think I have it anymore, but I will look.  Roger might be able to put you in touch, since he's on the field there at Ryan.  

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You don't need a certified welder. That break is easy to weld. The new cost may be more than you think because they come in pieces and need to be welded and you better pray that welder can get them perfectly lined up. Better to weld the old.

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On 11/2/2018 at 10:05 PM, Madhatter said:

I wonder if a good header wrap would buy time to land without any heat damage

I doubt if it would make a difference.  The gasses coming through there would probably shred the wrap in seconds.

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Lubricate the ball joints and balance your props.  The former is even written in the manual and is a cause of exhaust cracking because dry joints sieze up and the heat expansion leads to cracking.

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On 11/6/2018 at 3:11 PM, Anticept said:

Lubricate the ball joints and balance your props.  The former is even written in the manual and is a cause of exhaust cracking because dry joints sieze up and the heat expansion leads to cracking.

I know lubing the joints should be done, but at what interval?  Is there a way to do it without disassembling the entire exhaust system.

I did my joints with my rubber change, but I'd hesitate to take it all apart just to lube the joints, since it could create exhaust leaks or maintenance-induced problems.

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No interval specified.

Use nickel anti-sieze as well. I know copper is standard, but copper and stainless steel are incompatible metals. It's not going to fail necessarily quickly, but still.

Nickel often has to be special ordered and isn't cheap, but I find it lasts for quite a while. Applying it ever few hundred hours has been enough for me.

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