I've been getting e p0420 code recently so a repair shop told me it needed a new catalytic converter which is, of course in someone's infinite wisdom, part of the exhaust manifold. Took the manifold off. All bolts came off relatively easy, but i noticed the two closest to the firewall seemed really loose. When i got it off I noticed the gasket was black in that area. Went to put a new cat back on and while following the torque sequence i found that number 8 doesnt catch like it should. This is the one closest to the fire wall and right there where the gasket was black. I'm thinking someone stripped the threads in the head and it has been loose allowing gasses to leak at that area causing it to throw the code.

Of the 9 bolts 7 were true bolts and 2 were studs. I believe number 1 was a stud and this number 8. When i went to get a kit they gave me one with all studs. I've looked up heli coils or drilling and retapping. Think im going to get the new stud set and see if they work. Any advice?

 

MOVED from the Drivetrain section.... where it states: "This section is an archive of older posts, please post new questions in the specific model section. Thank you!"

I5 H3s have two Cats. A cat in the exhaust before the resonator, and the second is the mini-cat in the exhaust manifold you are talking about.

The I5s are notorious for breaking off exhaust manifold bolts, you may have the tip of the old bolt still in there, or as you said, it got loose and tore up the threads overtime.

 

Probably need to run a tap in it to check threads. If bad get a helicoil repair kit. It will come with the special tap and new threads. Just don't over torque once installed. Kits aren't much.

 

Update:

Ended up buying a time-sert kit in M8 x 1.25. Kit comes with a drill bit, countersink, tap, installation tool. I read from mechanics and machinists that this was a preferred method consisting of a steel insert. You drill out the hold, use the countersink bit which keeps the insert from threading in, tap the new threads, use installation tool to thread and expand the lower portion of the insert locking it into the aluminum. Once you remove the tool you can thread in a new bolt.

Upon drilling I noticed the drill stopped biting and no shavings were present. When I pulle d the bit out, something came out with it...part of a bolt. It appears a bolt broke off and someone drilled out the bolt at a slight angle which kept part of the threads intact. When I did my drilling those threads released and the hold was no longer the size of my insert. Not good. Thought about retapping and going up a size, but I'm not sure how much metal is there and I don't want to lose any more than I have to.

Contacted Time-sert and they suggested Big sert which is a thicker walled insert designed for repairs that had failed. I'll still have to open up the hole slightly and tap. The inside diameter is still going to be M8. These kits are a little expensive, but I like the idea of something keeping the insert from threading in or out and it is worth the money if it works. The Big sert kit is on order and should be here tomorrow. I'll install as soon as it stops raining.

 

take lots of time...good luck...