Davidv Posted April 21, 2020 Report Posted April 21, 2020 Over the last year I noticed some increased pitting on my turbo transition exhaust piece (see pictures below). I was keeping an eye on it but recently another A&P suggested that I take action as it was getting a little worse. As many of you know, there's no good way to tell exactly when this piece is going to go, but when/if it does it will be pretty catastrophic. Unfortunately, none of the traditional welding companies (Acorn, Knisely, ect…) are willing to repair it since it's cast. I wanted to share this experience because we found a tear in the slip joint after removal. This separation would have been nearly impossible to spot without removal since it's obscured on the backside of the v-band clamp. We also put oil on the outside of the transition piece to see if any of this pitting had resulted in actual holes. Sure enough, we got some staining on the inside (see photo). As I flew my plane to the shop this morning and it performed perfectly I started second guess my decision to change the part since it's fairly invasive. However, now I'm very glad that I did! The transition piece was the original from the factory so I'm not trying to scare anyone, but it may be good to have yours removed and checked if it has been a while. Below are some pics including the before picture, tear, inside staining, and final replacement installed. 2 Quote
alextstone Posted April 21, 2020 Report Posted April 21, 2020 Wow, great PIREP! I'm almost afraid to ask but how much did the new transition cost and where did you find one?Sent from my Pixel 3 XL using Tapatalk Quote
LANCECASPER Posted April 22, 2020 Report Posted April 22, 2020 3 hours ago, Davidv said: Over the last year I noticed some increased pitting on my turbo transition exhaust piece (see pictures below). I was keeping an eye on it but recently another A&P suggested that I take action as it was getting a little worse. As many of you know, there's no good way to tell exactly when this piece is going to go, but when/if it does it will be pretty catastrophic. That's a good A & P! No one likes to hear that they are facing a significant expense. But that good eye and good advice may have saved your life. Now for the bad news, if it was run that hot before you owned it, I would save up for the rest of your exhaust system. It's probably not too far down the road. 3 Quote
carusoam Posted April 22, 2020 Report Posted April 22, 2020 Let’s invite @M20Doc to have a look-see at that... (Bravo exhaust transition with the mumps) Looks like the porosity of the cast piece has become an issue over time... Nice to see that it is something that can be seen changing externally... Nice catch David! Thanks for posting all the details... Another MSer has changed out that transition before... there was a discussion regarding sourcing the replacement part... Best regards, -a- Quote
Guest Posted April 22, 2020 Report Posted April 22, 2020 (edited) If I’m not mistaken the failed part is a thin metal pipe and flange which is a slip fit into the cast transition not actually part of the transition and could be replaced on its own. A good practice is to pressure check the exhaust system with a shop vacuum cleaner, then spray every down with soap and water to find leaks and cracks. Clarence Edited April 22, 2020 by M20Doc Quote
LANCECASPER Posted April 22, 2020 Report Posted April 22, 2020 Wow, part #9, just the flange, lists for $1509 on Aircraft Spruce, making the gasket, part #10, seem like a bargain at $273.95. Quote
Davidv Posted April 22, 2020 Author Report Posted April 22, 2020 That’s correct, the flange could have just been replaced. However, given the pitting and 2400 hrs in service, several of the welding guys said it would be a good idea to replace the transition. I’m not sure whether the pin holes in the cast piece discovered afterward would have become a major issue shortly or not... Quote
philiplane Posted April 22, 2020 Report Posted April 22, 2020 12 hours ago, LANCECASPER said: Now for the bad news, if it was run that hot before you owned it, I would save up for the rest of your exhaust system. It's probably not too far down the road. The transition takes the collective heat of all six cylinders, and it's bolted to the hot side of the turbo, therefore it will suffer more that the other parts. I wouldn't worry too much about the rest of the exhaust. Just make sure the slip joints are lubricated every 25 hours. 2 Quote
alextstone Posted April 22, 2020 Report Posted April 22, 2020 Hi @philiplane, What do you recommend for lubricating slip joints...mouse milk? Quote
Davidv Posted April 22, 2020 Author Report Posted April 22, 2020 Thanks @philiplane, as you recommended when I saw you a few weeks ago, we lubricated all of the joints before putting the cowl back on and everything seemed to look alright (knock on wood)! Quote
philiplane Posted April 22, 2020 Report Posted April 22, 2020 Mouse Milk is good, unless you're in California. It's illegal to have it, or use it there. In that case, LPS-1 is a substitute. Not sure what the penalty is for illegal possession of Mouse Milk... Quote
carusoam Posted April 22, 2020 Report Posted April 22, 2020 @philiplane and @M20Doc... Can you take a second look at the cast part that was also found with an interesting challenge.... part number 13, exhaust transition? See the bumps on the exterior surface... and when a crack finding oil was applied... the oil went from the outer surface all the way to the inside of the cast part.... Ever see a cast part that had this kind of a porosity challenge? That cast piece is ugly expensive too... Wondering if there is a method of repair for that? Best regards, -a- Quote
LANCECASPER Posted April 22, 2020 Report Posted April 22, 2020 3 hours ago, philiplane said: Mouse Milk is good, unless you're in California. It's illegal to have it, or use it there. In that case, LPS-1 is a substitute. Not sure what the penalty is for illegal possession of Mouse Milk... I think it is the act of actually milking the mouse that's illegal. 1 Quote
philiplane Posted April 23, 2020 Report Posted April 23, 2020 7 hours ago, carusoam said: @philiplane and @M20Doc... Can you take a second look at the cast part that was also found with an interesting challenge.... part number 13, exhaust transition? See the bumps on the exterior surface... and when a crack finding oil was applied... the oil went from the outer surface all the way to the inside of the cast part.... Ever see a cast part that had this kind of a porosity challenge? That cast piece is ugly expensive too... Wondering if there is a method of repair for that? Best regards, -a- that particular part runs cherry red during flight with greater than 32" MP. The higher you go, the hotter it gets. At that point, the material degrades over time until you get porosity and cracks. It's the down side of a turbo system. You would need to ask your weld shop if they are able to weld & grind repair the porous spots. It can't be duplicated in the field and they generally don't use patch repairs on complex parts like that. 1 Quote
FoxMike Posted April 23, 2020 Report Posted April 23, 2020 When I have reassembled my Bravo exhaust I have lubed the it with LPS Nickel Anti-Seize. Mouse Milk works OK but this Nickel product seems to work better. 1 Quote
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