M20Doc

Check your exhaust

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I took these pictures of a 231 exhaust today.  We pressurized the exhaust with a shop vacuum and sprayed it down with soap and water.  I scrubbed the areas with a stainless brush and the hole just kept growing, it is just ahead of cylinder 5.  The second picture is a small crack in the stack for cylinder 1

Clarence

52B78824-64D2-4861-AF48-D3ECCFB90613.jpeg

31F40552-03FF-4BB1-878A-6C744C36129D.jpeg

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My CO detector went off showing 10 parts per million in November.  Had a small leak, that would only get worse so we pulled it and sent off for a repair.  Came back two weeks later completely rebuild for 4.5 AMU's.  

Pritch

exhaust.jpg

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Clarence and Pritch,

Any idea how many hours were on the exhaust systems when these events occurred?

Rough numbers will work...

Best regards,

-a-

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Ours failed in Dec. At about 700hrs. It was bad, turned on the heat and it was like sucking on the exhaust...because I effectively was.

If you zoom in you can see the crack. It was around the entire tube because I could move it by hand (slightly).

4 weeks later, good as new. acd2c9e6477f426181ac0ff2300b1891.jpga4ba50e8bb409d677fc9775bf64b84cf.jpg

Sent from my SM-G960U using Tapatalk

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12 hours ago, carusoam said:

Clarence and Pritch,

Any idea how many hours were on the exhaust systems when these events occurred?

Rough numbers will work...

Best regards,

-a-

Not sure of the hours on the exhaust, I suspect original with around 4000 hours, and evidence of a few repairs.

Clarence

Edit: 3870 TTSN

Edited by M20Doc
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On ‎1‎/‎10‎/‎2019 at 12:47 AM, carusoam said:

Clarence and Pritch,

Any idea how many hours were on the exhaust systems when these events occurred?

Rough numbers will work...

Best regards,

-a-

Mine had about 1800 hours

Pritch

 

 

Edited by Pritch
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Mine had about 2000 hours on it- cracked and the muffler was totally shot inside.  The previous owner had the IO-550 overhauled in 2013, but didn’t overhaul the exhaust at that time.  Here’s to another 2000 hours of service.

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Applying high-temp anti-seize to the slip joints helps prevent cracking (reduces stress) and makes it much easier to disassemble the next time. I recently had to R&R the Rayjay exhaust on my M20E because it was installed  incorrectly by a shop that should have known better. They didn't anti-seize the slip joints and it was a real bear to remove.

Permatex Copper Anti-Seize Lubricant

Aaron

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On 1/9/2019 at 8:49 PM, M20Doc said:

I took these pictures of a 231 exhaust today.  We pressurized the exhaust with a shop vacuum and sprayed it down with soap and water.  I scrubbed the areas with a stainless brush and the hole just kept growing, it is just ahead of cylinder 5.  The second picture is a small crack in the stack for cylinder 1

Clarence

52B78824-64D2-4861-AF48-D3ECCFB90613.jpeg

31F40552-03FF-4BB1-878A-6C744C36129D.jpeg

Maybe a dumb question but I am new to Mooney’s but just wondering if this is very common on the 231? Or Mooney in general? 

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6 hours ago, Sixstring2k said:

Maybe a dumb question but I am new to Mooney’s but just wondering if this is very common on the 231? Or Mooney in general? 

I’d say it’s common to all exhaust systems regardless of which airframe.  It spends its life heated to upwards of 1600 degrees and then being vibrated by the engine.

Clarence

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I’d say it’s common to all exhaust systems regardless of which airframe.  It spends its life heated to upwards of 1600 degrees and then being vibrated by the engine.
Clarence

I assume turbos are harder on exhaust components than NA?


Tom

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My muffler imploded with about 650 hours on the engine overhaul (don't know if the muffler was OHed then, replaced or untouched). Wish I had taken a picture but was too shocked. Found at first annual after moving back South, on the bottom and difficult to see until removed, where all exhausts joined in it had collapsed big enough to put my fist into. My CO-detecting dot showed nothing . . . . After reading Dan's experience here, I  bought a Sensorcon and am happy. Then I heard his story in person at The Mooney Summit and was even happier!

Watch your exhaust! Because you never know. Get a real CO detector, not a household unit that won't alarm until holding a high number for hours. 

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11 hours ago, aaronsn said:

Applying high-temp anti-seize to the slip joints helps prevent cracking (reduces stress) and makes it much easier to disassemble the next time. I recently had to R&R the Rayjay exhaust on my M20E because it was installed  incorrectly by a shop that should have known better. They didn't anti-seize the slip joints and it was a real bear to remove.

Permatex Copper Anti-Seize Lubricant

Aaron

Curious if maybe the Permatex Nickel based Anti-Seize would be better in this application?  It is rated for higher temperatures.   Just asking,  don’t have an opinion either way. 

Part of my oil change routine is to apply penetrating oil (Mouse Milk is my favorite) to all the slip joints.  I use a small syringe to dribble it in place.    Capillary  action will pull the oil into the joint,  even  the slip joints in a horizontal position.

Bill

 

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2 minutes ago, wpbarnar said:

Curious if maybe the Permatex Nickel based Anti-Seize would be better in this application?  It is rated for higher temperatures.   Just asking,  don’t have an opinion either way. 

Part of my oil change routine is to apply penetrating oil (Mouse Milk is my favorite) to all the slip joints.  I use a small syringe to dribble it in place.    Capillary  action will pull the oil into the joint,  even  the slip joints in a horizontal position.

Bill

 

Is mouse milk useful at high temp?

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24 minutes ago, Browncbr1 said:

Is mouse milk useful at high temp?

IIRC, Mouse Milk is required to be applied to slip joints of PowerFlow exhaust systems.  Hopefully an owner can chime in here.

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Gents,

Some things that are not communicated enough regarding exhaust systems.... (not to scare, or anything new.... just things to be aware of from a PP point of view...) so, communicating more is the intention of this post.

1) All exhaust systems can fail, by ‘wear’, or cracks...

2) Turbo systems are more susceptible, and can have more critical failures....

3) All exhaust system wear out slowly, the hottest parts are at the highest risk...

4) The two issues we want to be aware of is CO poisoning, and engine fires...

5) The tubes closest to the exhaust valves get the hottest and have a tendency to thin out...

6) The tubes that combine multiple flows of exhaust have an ever higher average internal temperature...

7) The tube that combines flows into a turbo is extra special... it is at the highest temperature and is under a higher pressure than any Normally Aspirated exhaust, and is often held in place with a one-time-use V-clamp...

8) A crack in any exhaust system leaks CO, if it leaks CO in the muffler under the heater muff... This is the delivery method of getting CO into the cockpit...  CO monitors are important tools to be aware of such problem... (get one)  Ask @DanM20C if you need assistance...

9)  A crack, or failed clamp before a turbo system can become a ‘land now if not sooner’ kind of issue... hot EGT gasses escaping under the cooling can be like a cutting torch in the vicinity of fuel and oil lines...

10) Proper Maintenance history is very important, as is all maintenance... lubricating slip fittings is an important method of eliminating crack promoting stress.  Proper torque or re-torquing exhaust V-clamps is critical.  Do not re-use parts that are one time use only....

Summary...

  • CO issues
  • Fire issues
  • Thinning exhaust tubes of hot sections
  • Proper maintenance 
  • Applies to all planes, not Mooney related.
  • Turbos have higher pressure and EGTs constrained in the exhaust system compared to NA engines.  Open ended exhausts allow for adiabatic cooling.
  • Hours take their toll.
  • Be looking for thinned walls, unusual temperature marks, exhaust stains, erosion of metal and welds...
  • CO monitors have been incredibly helpful for alerting of some exhaust issues early on...

PP thoughts only, not trying to generate a scare, not a mechanic...

Best regards,

-a-

 

 

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35 minutes ago, Andy95W said:

IIRC, Mouse Milk is required to be applied to slip joints of PowerFlow exhaust systems.  Hopefully an owner can chime in here.

I don't know the specs of Mouse Milk. PFS recommends and sells a Loctite copper based anti seize lube rated to 1800f. (Actually they give out 4 oz "barrels" at the air shows. I apply at each annual and after 7 years I have no problem disassembling the exhaust.  

https://www.powerflowsystems.com/items.php?fi_id=13

I could be corrected but I suppose that lube would be appropriate for slip joints other than PFS. 

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23 hours ago, Andy95W said:

IIRC, Mouse Milk is required to be applied to slip joints of PowerFlow exhaust systems.  Hopefully an owner can chime in here.

In a brief search I can't find a spec on Mouse Milk. I note it is sold as a "penetrating oil" that is effective as a cutting oil. I did see a comment that it is "unaffected by temperature". Whether it has a long lasting anti seize properties is not clear to me. I suppose it might be the right stuff for a slip joint that was seized due to lack of prophylactic lubrication. B)

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Apparently, mouse milk is a brand name...?

I have seen it referred to Often when lubricating turbo pressure controllers and waste gates...

Pressure controllers, waste gates, and slip joints may be different in their viscosity needs...?  

A reference for MouseMilk can be found here....

http://www.ramaircraft.com/Maintenance-Tips/Turbo-Wastegates.htm

 

oddly no mention of lubricating exhaust parts mentioned here...

https://mousemilk.com/

 

Best regards,

-a-

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