How to: fix your broken downpipe o2 housing bolt
 

Don't be an idiot. If you are going to reinstall the downpipe bolts, ANY bolts, use anti seize, always. Please.

If you are dumb like me, you may have forgotten this little tidbit of advice. In any event, you may have also cross threaded your bolt into the o2 housing. If the bolt is stuck and no amount of wrenching with a regular ratchet will suffice to remove it, you may need to follow this how-to.

Things you will need (check OSH, Home Depot, Sears, Lowes, Ace, etc.)
*safety glasses*
11/32nds drill bit (cobalt preferred; we're working on cast iron and heat-treated steel here)
10mm x 1.25 tap
tap handle to match the tap (3/8" most likely)
cutting fluid
proper corded drill or powerful cordless drill
cutting bit (disc-type for hard metals)
conical or bullet-type filing bit
3/8" ratchet with 10mm/12mm/14mm sockets, 6" or more extension (to reach downpipe bolts)
breaker bar (to fit your 14mm socket)
high temp antiseize (permatex @ autozone)

-------------------- take a deep breath -------------------

Step 1
Take a breaker bar to that bolt. It will likely break right off in the o2 housing. If you are able to extract it but find that the threads are focked up, skip to step 4.

Step 2
You are staring up at your o2 housing looking at the bolt broken off in the hole. Nice. Grab a :beer: or 20, you will need them. If the broken bolt is flush with the o2 housing, skip the cutting detailed below.

Break out a dremmel with a cutting bit, or a drill with a similar bit. Cut the bolt flush with the o2 housing.

You may then wish to use a conical or rounded tip filing bit to create a concave surface on the broken bolt shaft. This will be useful for centering the drill bit later when we drill this bolt out. This is pretty important, because if you get the bit off-center by even a bit, the bolt will not line up through the downpipe flange later!

Step 3
Now you have a good starting point on the drilling. Unfortunately there is a LOT of sh~t in the way of getting a proper drill up in there, so you may want to follow steps 4-5. If you have a long enough drill bit or can fit a drill up in there around the i/c piping and plastic undertray, go right ahead and skip to step 7.

Step 4
Remove the lower tie bars to get access to the downpipe. Remove the downpipe bolt remaining (if there is one, or you may have very well broken both, in any event it should be freed from the o2 housing). Remove downpipe from the cat, then the hangers. Get that thing out of the way (the downpipe).

Remove the entire plastic undertray. This is necessary to remove the MAIN plastic part (the biggest of the 3) to get proper access to the downpipe bolts. Have fun with all those clips. The best method I've found is to LIGHTLY unscrew the center part, then grab a pair of plyers and pull the center out. Trying to unscrew them all the way will simply result in them popping right back in.

Step 5
Remove the front bumper. See this write-up for details (steps 1-8):
http://www.evomoto.com/tech_info.php...3_10&tech_id=8

Step 6
Remove the passenger-side lower-i/c flex piping and hard piping. The hard pipe is held on with 2 12mm bolts. You'll see it plain as day. Unclamp after the bolts are out, and you can remove the hole thing from the pass-side flex pipe off the intercooler itself.

Step 7
Now you have CLEAR unadulterated access to the o2 housing bolt holes for most standard size drills. I recommend a rather powerful corded drill, mine is a 5.5amp unit from Craftsman. Not all that expensive, but plenty powerful.

Drip some cutting fluid onto your drill bit. Line up the drill as STRAIGHT as possible, this is extremely important!! You do not want to drill a hole which is crooked or off center. Begin very slowly, you should begin to see shavings almost immediately. Every few seconds, stop, clean off the bit and the hole, and start again, occassionally adding more cutting fluid. Once you have a hole beginning to form, go ahead and start increasing your drill speed but take it easy; you do NOT want to get this off-angle. Drill all the way through the o2 housing flange. Clean out the hole once you are done, I used a bit of WD40 and a twisted-up shop towel. Let it dry before proceeding.

Step 8
Now you may begin the tapping of the hole. I recommend using a tap handle rather than the drill; it will make for a more precise/less apt to get F-ed up hole once you are done.

Start by dripping some cutting fluid on the tap, then again, with a PRECISE motion, start the tap in the hole as straight as possible. It's got a bullet head so it shouldn't be too difficult. You will feel a lot of resistance, every turn or two you should back the tap out, clean it off, clean the hole, and begin again with more cutting fluid. The idea here is the cleaner/more lubed, the better. Think sex. ;) Clean that thing out when you are done.

Step 9
So you have a tapped hole and everything looks good? Put antiseize on your new bolt and try it; it should work in there VERY nicely. Just use your fingers, don't force it. If you find it's not fitting properly, clean it out and run the tap through it again slowly. If that never works, you may have screwed up the hole again and will likely need to replace the o2 housing... sorry.

Step 10
To ensure that you are good to go, mount the downpipe to the stock hangers. Line it up w/ the gasket (as necessary) to the o2 housing, then lightly and easily thread your antiseized bolts into the housing. I say go 2-3 threads with each bolt at a time to ensure that the pipe doesn't twist and cause you to insert them at an angle. Once you have ensured fitment, go ahead and bolt it up to the o2 housing and torque to spec. THEN mount it to the cat. Mounting to the cat first will create lateral stress on the dp->o2 housing bolts and you may have to cry and start all over again! Just don't do it.

Step 11
Put everything back together and verify that you have no exhaust leaks. You should be good to go.




I hope this helps anyone else out who f-ed their bolt(s) up and is looking for evidence that it's not TOO hard to fix.