Do you have experience with this Jake? Doing that would be my preferred method to get it fixed but i'm just completely out of my realm of experience on this one. I'm looking at the timesert thread repair
https://www.amazon.com/TIME-SERT-Metric-Thread-Repair-1212/dp/B001ZS2BJ4/ref=sr_1_fkmr0_1?ie=UTF8&qid=1502723599&sr=8-1-fkmr0&keywords=time+set+12mmx1.25

it's on cylinder four so access is about as best as one could ask for.

Your thoughts?

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

Phil, personally I was looking into it and thinking about it. The timsert would be a better more solid than a helocoil. Although both would work. It is your best option. It can be done either and save your friend alot cash on machine shop repair.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k