Well ever have one of thse days ..... 2001 durango 5.9 thermostat needed changing , decieded to replace it... installation was a piece of cake untill .. the last bolt on the houseing snapped, As this was the first time for me drilling a bolt out somehow I've managed to drill a hole to the left of the bolt ( target ) and on my 2nd try made on to the right of the bolt ( target ) since then ive managed to hit my target, My question is what can i use to fill these two holes ?
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When you're trying to drill and easy-out a busted bolt, it's always best to use a center punch to get your bit centered on the broken piece so the bit doesn't skip.
As for filling the mistakes....is that aluminum, or cast? And how big are the holes? If they're pretty big, I suppose you could use JB Weld, but I don't know if it'll leak or not. I'd think it wouldn't, but you never know. If it were me, I think I'd either pull the intake and replace it, or braze (or heli-arc) it back up, then re-drill and re-tap it.
If they're small (under 1/8th") and will be covered by the gasket and housing, you could probably just fill them with silicone and not worry about it at all.
Out of curiosity, why did you keep going when your bit skidded off the bolt?
i had that happen on my old cougar. i haven't looked at the housing but i know on the car i was able to ditch the gasket and i used a copper color gasket maker silicone to seal it and then i put a screw above the old hole and one below. not the best idea because my housing was screwed after that but it held up for 2 yrs until my sister wrote the car off
+1 on the picture...I was thinking the JB weld was a good idea,or mix a small unit of West System and cavasil filler just becasuse it could drilled and tapped but without a pic there's no way to tell...
If the bolt is broken far enough above the surface to get an air hammer on it, squirt it with break-free and hit it with the air hammer for 5 or 10 seconds, it'll come out easy. If not, then you might end up having to heat it.
Before you turn T-stat housing bolts, you should always, ALWAYS give 'em a few good whacks with a hammer, that'll usually keep 'em from twisting off.