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Cylinder head thermostat housing boss broken

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89 MJ 4.0L 2WD AUTO 140k - found this delightful surprise while going after the thermostat - lower mounting boss broken off - previous owner busted it and basically RTV'd thermostat housing  it in place - any suggestion to repair without pulling head would be appreciated - reman CYL head #2686 is hard to find / expensive. 


Comments on these ideas appreciated

1) clean thoroughly and JB Weld a helicoil in place and use smaller fastener

2) drill into water jacket / tap and use longer fastener - seal with #2 permatex

3) add 2 smaller adjacent fasteners into the cylinder head face on either side of the busted one


Any other approaches would be appreciated


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I might try modifying option #1.  I would use a Keensert or such. I could also see making an insert with a flange that would be counter sunk about a washers width. Then epoxy into place. Possibly combining with squaring up the back. Add washer and a nut. 

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My bad - I see that bolt ought to be 5/16-18 - I would be keeping same - the current bolt is chewed up so I got the thread size wrong - I’ll also be making a temp jig to guide the drill once I determine the thermostat housing hole to hole distance - thanks for the feedback on the bolt 

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