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2014 Peterbilt 389, the flex pipe on the exhaust keeps cracking all the way through about every 2-3 months, has anyone else had this issue or able to recommend a fix? Thanks. [attachment=2778]

If it's still mandated the flex would be subject to a lot of moisture.

(05-06-2017 )Signature620 Wrote: [ -> ]If it's still mandated the flex would be subject to a lot of moisture.

Nope, all that is gone.

Cracking on both sides like that would lead me to believe your not getting enough flex. On my Pete when it gets too much flex say from a bad mount bushing they only crack on one side. Maybe check and make sure the flex section is not too long and is being forced in there between the two clamps.. It's either too much or not enough flex causing that.... I may be wrong but that's one place you can start in your search to fix

(05-06-2017 )Rounded_nut Wrote: [ -> ]2014 Peterbilt 389, the flex pipe on the exhaust keeps cracking all the way through about every 2-3 months, has anyone else had this issue or able to recommend a fix? Thanks.

I think you would have better luck using stainless flex

Replace the flex pipe and leave the exhaust hangers for the hard pipes a bit loose, but not flopping around for a couple days so that heat expansion and settling can set in. Then gently tighten everything up but don't make them real tight. All those pipes and exhaust components need room to stretch in the heat and flex when the frame flexes too. It sounds like someone is tightening everything up too much, possibly using impact guns instead of doing it by hand.

While your at it, check your rear motor mounts very well. Look for cracking in the rubber, etc. It could be that your engine is moving around too much.

Just some thoughts of my own on it.

Hard to tell from the photo, but it almost looks like the flex pipe is a bit short for your application. Is it an aftermarket pipe or is it an OEM? I know when working on my exhaust, like Rawze stated, loosen everything and let it fall into its natural position and then hand tighten. And check the engine mounts and all of the hangers. That one hanger on the passenger side holding that elbow (off the frame rail) to your DOC should be hanging straight down I would think, instead of at that angle. Looks like something was forced in to position or something is not sized properly under there is my best guess. Another place to avoid aftermarket parts on these mandated trucks.

Good points thank you for the starting points; the parts replacer at the shop uses his electric impact almost exclusively, so I'll be taking some parts home!

Look at the picture, it is compressed completely. It can't flex installed this way so it breaks. Replace it with STAINLESS STEEL flex in a relaxed position, not compressed or expanded. give it the ability to flex and you should not have any problems.