I have a 2013 F350 with a 6.7L engine. It has 43904 miles on it and I had the exhaust separate just beyond the DPF. All three bolts that hold the exhaust section to the DPF failed. The bolts failed dead center right in the middle where the seal is. There is surface rust but the nut is solid with no flaking and the threads on the back end where the nut is are clearly visible and solid. This is a punch bolt similar to a wheel stud and the head is securely fastened has it’s shape, is solid, and has no flaking. You will not get a light and engine noise will not change. There are no sensors on this section and it looks like the only purpose this pipe is to get the exhaust to the rear of the truck. Only way to catch problem is with a visual inspection. Looks to me like bolts failed because of heat. Dealer felt it was rust related even though head and nut of bolts were solid. Looking over my Ford Emissions Defect Warranty and Emissions Performance Warranty this part is not covered. Dealer said they had never seen this before. Here is my question. Has anyone experienced this same failure and how hot does the DPF get during regen? These bots would be the first thing exhaust gases reach after the DPF and to me they do not appear large enough to handle it. On a side note I owned a 2000 Ford Excursion V-10 and sold it 3 months ago In 17 years not one part of the exhaust ever failed. It was exposed to the elements including road salt in the Northeast.

 

I'm going to have to check mine. According to my Scangage II the the temps reach 1200 deg F. during a regen .

 

Just found this. Great info on DPF and exhaust temps from the US Forest Service.

https://www.fs.fed.us/eng/pubs/pdf/08511816.pdf

 

One of my bolts broke a while back, maybe 2 years? I was just doing an oil change, and caught it during the inspection. I knocked the offending bolt head out and grabbed a new bolt. Been fine since.

 

Is that picture before or after the repair? The bolt looks to be a little loose to me.

 

I had this exact failure on my '13 as well. Bought a new gasket at the stealership and replaced the offending bolts. Should it have failed? Of course not. But its not worth my time to even schedule to have the dealer fix it. I'm well out of warranty even if it were covered. I think the parts and having someone with a lift swap the failed bolts cost me under $40.

 

That pic is from when i first suspected something wasn't right.

 

I think I will start checking these every other oil change. Sounds like a punch and brass hammer should do the job if needed. I will even replace with stainless if it happens again. I really thought it would have been covered under the Emission Warranty of 5 years and 50K miles. Live and learn. Dealer cost for this job including tax was $215.56.

 

Did the bolt break from rust/corrosion? Or was did it break from stress? If it was the latter then a stainless steel bolt may not be the way to go as it would possibly be less strong that going with something like a grade 5 bolt.

 

No obvious cause that i could tell. Exhaust hardware does this kind of stuff occasionally, i wouldn't put a lot of thought into it.

 

Thought I would post the fixed photos. Dealership put these 8.8 bolts in. I'm not sure but I think these are medium grade metric bolts. After looking at these photos I still feel this was a stress/heat related failure. The bolts failed in the middle where they are covered by the exhaust pipe and gasket. The head and nut are exposed to the elements and they still looked good on old bolts. I agree with the comment made in this thread earlier about not using stainless steel bolts. I know stainless can't handle as much stress so in the future if I need to do the repair I will do it myself and use a high strength bolt.

 

Better photo of the fix.

 

Ford that price you could have bought the bolts and a gasket if needed and done it yourself, but at least they didn't tell you something like you need a whole new exhaust at untold thousands of dollars

 

Those flange nuts are not meant to be used with a washer or lock washer.

 

I was going to ask about that as they look like what I would call castle nuts -