Openflash Header exhaust leak
 

Recently installed my OFH and I heard a slight hissing noise, and thought maybe it was just rasp. I was also experiencing wacky LT fuel trims at low rpm, light throttle. I thought maybe the car was still learning and they'd settle.

I got under my car today and plugged one exhaust tip with a rag and put a Shopvac blower in the other exhaust tip. I have a major leak at the header to overpipe connection at the top and bottom of the flange. I used all new Grimmspeed gaskets, and everything is torqued as tight as can be. I tightened from front to rear, and I can see a noticeable gap between the flanges on top and bottom.

I'm a little pissed that I spent $50 on new gaskets and have a leak (not that it's the gasket's fault)

Did I do something wrong? Where do I go from here? I feel like a new gasket isn't going to solve this issue. Should I try an OEM Subaru gasket or just take it to a shop and have them attempt to fix it?

try two gaskets stacked up, helped fix my leak between overpipe and front pipe

This worked for me as well (header->over-pipe connection)

I have seen a couple people complaining that their new GS gaskets and installed headers are encountering leak issues. I love GS and their stuff is definitely built with passion, but things can go wrong.

Properly torque your header by the way, don't just wrench on it until it's mass tight

@Decay107 @malubawla Think it'd be safe to use the current Grimmspeed gasket and add a Subaru one? I'm weary of doubling up gaskets but I don't see another solution at this point.

@Koa I've heard 22 ft/lbs at the header to block and 26 ft/lbs at header to overpipe?

Yes use the OEM gasket.. Can even use your old one if you clean off all the soot and use a hammer to pound it flat. And I go 30 or so for exhaust but yea, they're really not that tight! It's tempting to just wrench on it until it's real tight, but many have found that method results in broken studs

P.S I love my OFH, I bet you will too once it is up and working well!

@JB86'd - I've been having the same issues with the leak. I think I've tightened everything like 3-4 times now. It goes well for a few days to a week but then I start hearing that hissing/fluttering sound again. I always find the header bolt/nuts to be loose and I keep re-torquing them to 22 ft/lbs. I was going to write a post about this to see if anyone can offer a solution. Is there a way I can find where the leaks are without the shopvac? I've heard the soap water test works too but still not sure what I can do about the header bolts that keep coming loose.

also - like you my LTFT are off too and I think my MPGs have suffered due to that.

Also, also - can a leak from the header to OP cause LTFT to be off?

@ap5512 I haven't had an issue so far with bolts coming loose, have you tried a different torque wrench? Maybe yours if off a bit. Try going to 30 ft/lbs. My issue is the top and bottom of the flange not being flush, so it leaks bad on top and bottom. I'm sure the LTFT issues you're seeing are from the leak..as are mine.

I just went and loosened everything, and reinstalled, using the old Subaru gasket and my newish Grimmspeed gasket stacked, with permatex silicone copper "liquid gasket" inbetween the gaskets and on the flanges. I'm going to let it cure overnight and give it a try in the morning.

I removed the bolt from the exhaust hanger that hangs from the rear of the transmission to give some flexibility when tightening the rest of the bolts. After installing the header, it doesn't exactly line up anymore, and I have a feeling that's what was causing some increased NVH. Is there any potential damage leaving that bolt off could cause?

I doubt you will cause any damage if you don't put it back right away. I think it may even help get everything into place again with the cool/heat cycles. I'll have to give it a try again too and maybe I'll put some permatex liquid gasket myself. Good Luck..

So I tested my exhaust using the shopvac blower and soapy water spray, it seems so far the double gasket and permatex silicone copper has fixed the leak. I'm going to drive it for a week and retorque the bolts and double check for leaks. After fixing the leak my car got A LOT quieter and better sounding.
@ap5512

Let me know what the logs say to regarding the LTFTs. Thanks!

I had a leak in the same spot too - the flange wasn't flat at all! Check if that's the problem (it seems like it is) and if it is, notify the OpenFlash people. I tried OEM and GrimmSpeed gaskets too and that wasn't the issue. The flange was just way too bent for any gasket to make a difference. My local tuner shop fixed it but definitely let them know about the issue because they said I was the first to have a bent flange.

I didn't check the flanges before installing because I assumed the header was perfect quality and it was not the case.