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.

My flange didn't even line up to my stock exhauat, it's at a different angle, and the flange leaked on top and bottom.

Same here, leaked at top and bottom and I also have stock over pipe.

I undid the exhaust hangar bolt to help line up the flanges, so after tightening everything up that back bolt was misaligned by about a half inch. After putting that bolt back on I could feel the tension from the misalignment , so I ended up leaving it unbolted and put some padding and heavy duty zip ties so it was under less stress. What was your experience with that?

It was a few months ago when I installed it so I can't remember if everything aligned perfectly. But I don't think it was too mis-aligned since nothing really sticks out in my memory of the install. Either way, the leak was caused from the flange not being flat. I don't think that amount of tension would cause the flange to bend. I'm pretty sure it came like that, like in my situation.

I had to tighten up the exhaust hangar bolts to get the two flanges to align (I had the bolts loose because I took the hanger completely off to remove the OEM Header)

Do you have datalogs before & after the leak? I'd be interested in seeing the difference.

Hmm my experience was the opposite, after installing, mine was misaligned. I don't know what to make of it.

I posted a limited datalog while I had the leak..the LTFT while WOT were really not off too far, but I was seeing high st and lt trims at low rpm low throttle. I fixed the leak, and just tonight flashed a revised tune with some timing pulled for my shitty 91 oct. I'll do another datalog next weekend, out of town this week for work.

I'd say likely an alignment issue with the OFH, it makes sense to me that the OFH should line up with the overpipe when the exhaust hanger is torqued.

http://datazap.me/u/joshbustos86/206...g=0&data=1-8-9

However from your last log I can't really see anything that would indicate signs of an exhaust leak, with a leak I'd imagine your trims would be messed up across the board, not just at low RPM. This kinda boggles me a bit.

I thought it was an installation error but all my components are stock, and I've installed multiple headers..must be the header itself.
That's what I thought, but Steve99 told me that sometimes it affects low rpm light throttle more than high rpm. I thought I didn't have a leak, but when I tested it with a shopvac I had MAJOR leaks on top and bottom of the header to overpipe connection that I could hear and feel, confirmed by soapy water spray too.
I will take a new datalog after I put some miles on this tune without a giant leak in it and post it asap!

Hi guys,
All the OFHs are test fitted on the same jig before they are shipped out so the chances of one being out-of-spec is close to nill. But if there is a flange that is not perfectly straight, that's easy enough to verify with a ruler. In that case, please email pictures to us at sales@openflashperformance.com and we can absolutely replace it. Out of the few hundred OFHs we have sold, we have only had 2 warranty case so I'd be surprised if any header is out of spec. But anything is possible and we will remedy the situation to the best of our ability.

Interesting... I just read this a bit ago so I guess it makes sense.

"Use Fuel Trim to Diagnose Vacuum and Fuel Delivery Leaks. With the engine idling, look at the Short Term Fuel Trim (STFT) and Long Term Fuel Trim (LTFT) values. Normal range may be high as plus or minus 8, but closer to zero is best. If the numbers are +10 or higher for STFT and LTFT, your engine is running LEAN. Rev the engine to 1500 to 2000 RPM and hold it steady for half a minute or so. If the fuel trim numbers drops back down to a more normal reading, it confirms the engine has a vacuum leak at idle. This is because vacuum leaks have less of a leaning effect on the fuel mixture as engine speed and load increase".

http://www.aa1car.com/library/what_is_fuel_trim.htm <- Reference

Shiv, thanks a lot for the response. I think I've fixed the leak on the top and bottom of the flange by doubling up gaskets. My only concern now is the slight misalignment of the flanges that's throwing off the whole alignment. I have the exhaust hanger bolt disconnected because it was misaligned and causing a lot of NVH when connected. Any advice or tips?

Hey man, sorry to hear that you're having trouble with your headers sealing!

With that said, I can absolutely promise you that the issue here isn't with our gaskets. We've sold tens of thousands of these gaskets and the only time when they don't seal well is when the two mating components have flange faces that are either a.) not flat or b.) not parallel. We know this because we also manufacture exhaust components and flange flatness and part 'warpage' are the major challenges.

One of the things that you might try is checking the header flanges for flatness individually and also between the two flanges. A lot of times just bolting them down will flatten any angular discrepancies between the flanges, but sometimes during welding, a header might pull just the right way and make that impossible.

In any case, I'd encourage you to continue using GrimmSpeed gaskets and to avoid double stacking them if possible. They aren't really meant to be a solution to fitment issues and sometimes double stacking will add enough thickness that other issues are created. In our experience, the guys at OFT are awesome, so maybe it's just a worth a call to them for some help!

Best of luck and let us know if we can assist in any way.

Matt Beenen
Engineering

@GrimmSpeed Matt I appreciate the reply. I have no doubts about the quality of the gaskets, just trying to get this all figured out. I'm going to go ahead and remove the header and check for flange flatness, as I have a feeling that is the issue.

My concern is that I have my header ceramic coated, so if it is in fact covered by warranty due to a defect, I'm still out $160 and whatever return shipping costs me, not to mention another week turn around time. @Shiv@Openflash

I had a similar experience, I unhooked my hanger bolts, and disconnected the front pipe from the catback to get the over pipe to line up correctly before I torqued it. Then the hanger bolts were a little off so I had put some pressure and flex the pipe to get it lined back up. following what shiv said:

All I can think is that everything has tolerances, and the header to overpipe is a compound angle. With play between the over-pipe/front-pipe, front-pipe/catback connection, and flexible rubber hangers. Some people have had variances in the position of their stock exhaust tips in relation to the rear bumper (eg one tip higher than the other), and I think you had to many pieces on the edge of the tolerance causing everything to add up in the wrong way. The flanges on the OFT are pretty thick, and since you already got it coated, you could just leave it on the car take it to a shop and depending on how far out they are, they may be able to just machine or file it to be more parallel with the over-pipe mating surface angle. Would still cost, but should be less than having to re-coat, or ship a new header.