uncle humjaba Posted May 11, 2013 Share Posted May 11, 2013 Hi all So this week I installed a CNT catted downpipe and 08 STI up pipe. After I throw everything back together, there's a pretty noticeable exhaust leak coming from directly under the down pipe. The problem is, I can't tell if it's coming from the down pipe or from the up pipe. Relevant facts: * I used new gaskets on both side of the up-pipe. I drove maybe 30 miles with the leak, and when I pulled it apart the gasket on the up pipe still looked new * I reused the down pipe to turbo gasket. I reused it when I pulled my factory DP for a clutch install 1200 miles ago, and it sealed back up just fine, so I thought I'd be fine this time * The nut on the very bottom of the down pipe is extremely difficult to get to, because of the way the CNT flange/bell mouth thing is cast. I could only get the open end of a wrench around it, and I'm not terribly confident it sealed very well * The down pipe did not sit flush with the turbo until I tightened the bolts to bring them together. I'm thinking this afternoon I may put the stock DP back on just to see if that fixes it. What would you do in my shoes? I've attached pictures of the up-pipe to turbo after installation (in the area where the leak would be, if it were leaking), and the hard-to-tighten nut. My roommate has suggested some high-temp RTV, but that makes me nervous, and seems like a messy solution. Link to comment Share on other sites More sharing options...
SpecBamf41 Posted May 11, 2013 Share Posted May 11, 2013 Regarded the nut you can't tighten. Can you swap a bolt in instead of a stud and nut? Or get a shorter stud so you can get a box end on it? Sent from my S3 BNR18g on 93oct Link to comment Share on other sites More sharing options...
uncle humjaba Posted May 14, 2013 Author Share Posted May 14, 2013 Stud goes into the turbo... The problem is that the flange on the nut touches the down pipe, not that the stud is too long. But, after feeling around some more, it feels like the gas is actually coming from below the flange... there may be a hole in the uppipe. Which would piss me off heh. Link to comment Share on other sites More sharing options...
korpsepatrol Posted May 14, 2013 Share Posted May 14, 2013 This is what I would do, others may or may not agree. First thing I would do is undo all of those and get new gaskets for anything dealing with up pipe and dp. Meaning Up to mani, up to turbo, up to dp. Get OEM but i hear people having good luck with grimmspeed double thickness gaskets. Dealing with pre and post turbo is normally where gaskets actually matter the most for leaks. After turbo to downpipe you can use any manufacturer gasket for your exhaust. After the gasket issue is no longer a problem i highly recommend you use OEM nuts for the turbo studs. If you use smaller or aluminum nuts they are prone to rounding. I have had it happen with the nuts that come with several aftermarket downpipes. Regarding not being able to reach that bottom one. You can reach it with the open side of the wrench. At times you will prob need a different manufacturer's wrench since some are made thinner than others. Keep in mind hand tightening won't help the situation. Whenever at all possible use torque specs on those bolts i believe its 35-36ft-lbs. For that bottom one you could do last and get it on there at about the same pressure by hand. Then go all around making sure they are all down just like you would with a wheel. Just my 2 cents... 2008 6mt Legacy Gt Spec B DGM - Not so Stock/Work in progress 2006 5mt Legacy Gt OBP - Sold 2005 5eat Legacy Gt OBP - RIP R.I.P Coxx Link to comment Share on other sites More sharing options...
km580 Posted May 14, 2013 Share Posted May 14, 2013 I had the same trouble on my '05 I got the Grimmspeed double thick gasket and never had a problem after that. Fat people are hard to kidnap!!! Link to comment Share on other sites More sharing options...
domoMKIV Posted July 9, 2013 Share Posted July 9, 2013 A couple months old but could still be helpful. Make a soap/water solution in a spray bottle and while the engine is cold, spray on the areas you think you may have a leak. When you start the car and the air starts to pass through you will see bubbles if air is escaping at the connections. I used this method to find my leak, turned out to be at the up/mani. Link to comment Share on other sites More sharing options...
stuck686 Posted July 12, 2013 Share Posted July 12, 2013 grimmspeed thick gasket might help I had my cnt dp flange sanded down a little because it had a manufacturing defect/gash in it that leaked. Link to comment Share on other sites More sharing options...
Brprs Posted July 12, 2013 Share Posted July 12, 2013 A couple months old but could still be helpful. Make a soap/water solution in a spray bottle and while the engine is cold, spray on the areas you think you may have a leak. When you start the car and the air starts to pass through you will see bubbles if air is escaping at the connections. I used this method to find my leak, turned out to be at the up/mani. Be sure to keep the soap and water away from your intercooler. Link to comment Share on other sites More sharing options...
imblaze89 Posted October 14, 2013 Share Posted October 14, 2013 I have this same problem with the bottom nut, did you find a fix? I mAy try the double gasket.. Also why is it bad for soap and water on the intercooler? Link to comment Share on other sites More sharing options...
1-3-2-4 Posted February 10, 2015 Share Posted February 10, 2015 A big exhaust leak in that area where the bolt is hard to get to will have driveability problems? Link to comment Share on other sites More sharing options...
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