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Strange engine part phenomenon

Jan 25, 2011
1,986
S2 11.0A Anacortes, WA
47D869B4-B5AF-4F8B-B50E-C28EAE69F45B.jpeg F15684DF-7876-4CE7-A845-06D0CE4583CD.jpeg 47D869B4-B5AF-4F8B-B50E-C28EAE69F45B.jpeg This an engine thing but I decided to post here. Most of you might remember that I ditched my Volvo MD17 a year ago and replaced with a Beta. When I did that, I saved a lot of the Volvo stuff to sell on CL or ebay. So, a lot of the Volvo stuff resided in boxes in my shop and garage for the last year. I have been slowly selling stuff off. Slowly...Four days ago, I started going through what I have and looking what has been selling on ebay. I have two exhaust elbows. One from my boat and one from an acquaintace’s boat..I was going to list my elbow and when I looked at it, it was cracked..it was not cracked three days ago and it has been sitting in a heated shop for a year since it was taken off the boat. Strange..F15684DF-7876-4CE7-A845-06D0CE4583CD.jpeg47D869B4-B5AF-4F8B-B50E-C28EAE69F45B.jpeg47D869B4-B5AF-4F8B-B50E-C28EAE69F45B.jpeg
 
Jun 11, 2011
1,192
Hunter 41 Lewes
just from the rust streak that is part of the crack I find that impossible.
 
May 29, 2018
94
Canel 25 foot Jonathan Shoigama, japan
Hmm. Not much chance of selling that.
So much for the quality of genuine parts.
gary
 
Oct 9, 2008
1,692
Bristol 29.9 Dana Point
Do you know anyone in your neighborhood who has a Volvo engine, who also knows that you have Volvo exhaust elbows in your garage?
 
Jun 4, 2009
3,152
Pearson 530 Admiralty Bay, Bequia SVG
If the hole was round, I'd probably blame cockroaches.
However, considering the rust, I think there has been a hairline crack (perhaps a casting flaw) for quite some time that may have even leaked a bit when warm and being used on the engine. Perhaps the shop just got warm enough that the crack expanded the full length of the casting flaw? A bit of duct tape and you should be good. People will buy ANYTHING on Ebay as witnessed by things like the Virgin Mary grilled cheese that sold on eBay for $28,000 back in 2004 and its knock off Jesus toast, along with a Corn Flake in the shape of Illinois that sold for $1,350.
 
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Likes: AlexB
Sep 30, 2008
1,426
Catalina 310 Quincy, MA
Do you know anyone in your neighborhood who has a Volvo engine, who also knows that you have Volvo exhaust elbows in your garage?
Lol. That's what I was thinking. We used to call that "Midnight Auto Parts".
 
Sep 9, 2009
3
Pearson P-26 Dana Point
While I am not familiar with the specific material used on the Volvo engine, I can tell you that there are certain materials which are know to suffer from "stress corrosion cracking". I learned that when I was working as a structural engineer on the Lunar Module (1968) at Grumman Aerospace Corp in Long Island , NY. We had LM 3 in the clean room (no possible corrosion there), yet a part installed in the Aft Equipment Bay was found cracked. I got all excited and phoned my boss (on a Sunday). He calmed me down and explained it was a new phenomenon just discovered in certain metals. If when they are fabricated, or installed and the part is under a constant tension stress, then a small crack will develop and the part will eventually crack (fail) with no other load on it. Aluminum 7075-T651 and other types of alloys that are very susceptible to stress corrosion cracking. So, it could be that the Volvo part was casted (made) with a residual tension stress in it (possibly during cooling), so it just took a long time (not loading) to crack it. For more information go to the Internet and type "stress corrosion cracking" and you may get a mouth full of information on the phenomena. We in the aerospace industry have learned what to avoid it in terms of material and alloys, but also in preventing "clamp-up" which leaves a tension residual on certain parts when they are attached on a not smooth surface.
 
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Likes: Tom J
Jan 7, 2014
41
Beneteau 45F5 51551 Port Jefferson
Could it be Hydrogen embrittlement? The bolt in the "cheese grater" building in London were popping off do to stress cracks caused by this. It happens in very hard steel. "single atoms of hydrogen enter the steel, migrate through the crystal lattice, and are attracted to the areas of highest stress. Here they cause tiny fractures to propagate and, in a worst-case scenario, a cascading effect can take place, as the stress increases and attracts more free hydrogen, leading to a sudden catastrophic failure"
 
Jan 25, 2011
1,986
S2 11.0A Anacortes, WA
This part is heavy cast iron. I inspected it very closely several days before I noticed the crack. It has never leaked in service. I would have noticed if it did. Strange that it would decide to crack after a year of being on the shelf...