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Broken Nuts.

S

Smilin' Jack

Well Known Member
Today during my first condition inspection while inspecting the exhaust a Vetterman 4 pipe I found on the #3 and #1 slip joints that the nuts were cracked. These are the small reference nuts that come with the exhaust
I replaced them with standard size lock nuts. Never seen a nut cracked before
Total time on A/C 153 hours Hobbs 122.6 on Tach.

15ees8h.jpg


2qmn406.jpg

Hope this might help some other RVers

Smilin'Jack
 
Wasn't there an advisory out a while back about bogus parts for these all-steel locknuts? I seem to recall there was, and cracking/breaking was the failure mode.
 
Whewh! I've got the crossover exhaust, not the 4-pipe, so I don't have to worry about it, right? :eek:

I do remember the issue a while back about substandard all-steel lock nuts, this looks like you might have gotten some of those.
 
Are those ms21042 nuts? Try using ms20500 which is a high temp nut.
 
Yep probably those nuts but what was funny was that while inspecting the exhaust the 2 cracked nuts were still in place. It was by chance that I caught it.

Really don't have a designation for those nuts since they were supplied in a bag of Hardware. They were the No 10 size.close tolerance nuts.

The exhaust system was purchased in 2013 new from Clint at Vetterman's.

Jack
 
Hi Jack,

Do you remember if the nuts looked like they were silver coated when they were new, or just like grey metal?

I got a handful of the super alloy - silver coated at OSH this year for FWF, it looks like I should be careful where they are used. I don't recall the number.

Good Catch BTW, it pays extra dividends to catch a root cause before it cascades to a major "event"
 
MS21042 nuts

Hi Everyone, the MS21042 nuts have been standard nuts on our exhaust and we have been using them for many, many years. We purchase ours from Aircraft Spruce, and while we are aware of the "bad batch" we haven't received any notice that we had gotten any of the bad ones.
The nut is used to hold the welded links together on the slip joints and isn't subject to nearly the intense heat of the exhaust pipe itself. While the MS21042 nut is only rated to 450 degrees, our experience has been very trouble free. This is the first time that we have seen one(s) fail like this on an exhaust installation. There are two things to keep in mind with the bolted joint like this: The nut only needs to be tightened enough to keep the bolt from spinning, and if overtightened, effectively eliminates the slip joint by seizing it up. Also, even if the bolts fell completely out, a properly installed tailpipe mounting kit will keep everything in place.
 
Thanks Clint for the reply, the exhaust was put on by fellow who built up my engine. So I have no idea how tight they were when installed.

Who know, but at least it bought the subject to light again and thanks for the advice on how tight to make them.

Jack
 
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