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Old 03-14-2013, 06:27 PM   #1
Acejam2k
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Default Exhaust leak on cold start only

Hey all,

It appears that I have some type of exhaust leak on cold start. It's cold here in MA during the winter. If I have the HVAC/heat on and start the car up, I'll smell exhaust fumes coming from the vents for about 5-8 seconds and then it will fade away. It appears that once the exhaust pipes get hot enough, whatever is leaking begins to seal. It should be noted this occurs when parking outside overnight (30* F) and when parking in my garage.

I'm running a stock VF43 turbo, Grimmspeed uppipe, Invidia Race header, and an APS catted TBE.
  • UP > Manifold gasket: 2x thick Grimmspeed gasket
  • UP > Turbo gasket: Grimmspeed gasket, a couple months old. I've pulled the turbo twice since installing, and I'm wondering if this gasket is leaking. I lifted the turbo to check, but I didn't spot any soot or unusual residue, so I put it back on.
  • Header > Block gaskets: Brand new properly torqued OEM gaskets.
  • Turbo > DP gasket: Grimmspeed gasket. I've removed the downpipe a couple times since installing, but the gasket did not have any unusual soot.
  • DP > Mid-pipe gasket: Grimmspeed 2x thick gasket with TONS of Permatex Ultra copper. No soot or residue, and I used a ton of Ultra copper so I'm confident this connection is not leaking.

I'm still a bit suspect of the downpipe to turbo gasket. I had to fix the passenger side intercooler mount a few weeks back. In order to do that, I had to lift my turbo up and move it to the side. Ever since I did that, I've noticed this exhaust smell more. However, it's entirely possible I've had it all along and just haven't really noticed it until now. A lot of times I'll start my car with the HVAC off, and in that case I wouldn't notice the smell.

Any thoughts? I'm wondering if I should pick up new OEM turbo to UP and DP gaskets since I'm a bit skeptical of this Grimmspeed stuff. I've ran OEM gaskets for 80k miles on both of those connections and neve had issues until I put on the GS gaskets.

On a similar note, I have also done the EGR delete. The solenoid that goes from the intake manifold to the turbo inlet on my car has been removed. The intake manifold is capped off, and so is the turbo inlet. The gas tank vent hose near the firewall is now routed underneath the car, and exits right near the rear mount for the front control arm on the driver's side. I know for a fact that this is supposed to create a smell by venting to atmosphere, but it's supposed to smell more like gas. Perhaps this has been the source of my smell all along, and I'm only noticing it more now since it's been colder out.

Thanks in advance!

- Ace
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Old 03-14-2013, 06:35 PM   #2
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take the little expandable dental mirror and move it around the joints were the gaskets are and see if it fogs up. or take a lighter and see where it gets blown out. No reason to start pulling every gasket off unless you know where it's actually leaking. Super easy to check for leaks.
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Old 03-21-2013, 10:47 PM   #3
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Quote:
Originally Posted by medamullet View Post
take the little expandable dental mirror and move it around the joints were the gaskets are and see if it fogs up. or take a lighter and see where it gets blown out. No reason to start pulling every gasket off unless you know where it's actually leaking. Super easy to check for leaks.
I tried using a mirror tonight and went over all of the exhaust flanges, including the header. No real noticeable fog on the mirror. I saw a tiny bit on at the UP to manifold flange, but I don't think this is my leak. I'm going to take off the 2x thick gasket that's in there now though, and swap back to a single thickness Grimmspeed one since I have an extra on hand.
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Old 03-22-2013, 12:35 AM   #4
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When its that cold Subarus fire up ultra rich and you're just smelling raw fuel. 8 seconds is not long enough to seal an exhaust leak so if you're not really seeing anything spitting water its not likely that. Recirc the air or turn off blower at cold start.
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Old 03-22-2013, 02:42 AM   #5
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Quote:
Originally Posted by Element Tuning View Post
When its that cold Subarus fire up ultra rich and you're just smelling raw fuel. 8 seconds is not long enough to seal an exhaust leak so if you're not really seeing anything spitting water its not likely that. Recirc the air or turn off blower at cold start.
Another thing to do is feel around the gasket areas when the cars cold and running. You will feel the air coming out if you have a leak.
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Old 03-22-2013, 04:53 AM   #6
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Your best bet is to find a piece of hose or vacuum tubing that is easy to move around and can get close to your ear. A couple feet long works. Put one end up to your ear and check the flanges with the other end.

You can reach far more places with this and it is not dependent on your vision or anything else. A good piece will even fit beneath heat shields. You will hear a distinctive difference in pitch and volume when there is a leak. May also feel a little heat

An old school redneck mechanic showed me this trick and i have found many leaks this way when other methods failed. You will also be less likely to burn yourself.

Good luck!!
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Old 03-22-2013, 10:21 AM   #7
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Originally Posted by aboothman View Post
Your best bet is to find a piece of hose or vacuum tubing that is easy to move around and can get close to your ear. A couple feet long works. Put one end up to your ear and check the flanges with the other end.

You can reach far more places with this and it is not dependent on your vision or anything else. A good piece will even fit beneath heat shields. You will hear a distinctive difference in pitch and volume when there is a leak. May also feel a little heat

An old school redneck mechanic showed me this trick and i have found many leaks this way when other methods failed. You will also be less likely to burn yourself.

Good luck!!
Well he said it leaks only when cold so i said just feel it out. I've always done this never got burned even on hot exhausts. Unless you have no nerves in your hands your brain should tell your hand to keep a good distance. I've used a/c leak detectors before also.

Another thing is this problem can occur more on an untrue flange in that case you may want to check with a flat sureface and a light or fealer gauge. If this is true you can try to mill it out with a grinder or have it machined.
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Old 03-22-2013, 02:31 PM   #8
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It's likely not a leak.

On cold start, the ecu runs ignition timing at 5 degrees AFTER TDC and it makes the exhaust very tinny and loud. Sounds like a leak. Then, depending on temperature it restores the timing to normal values (around 17* Before TDC) about 10-60 seconds after start. This is done to fire up the catalytic converter and minimize cold start emissions that the EPA is so retardedly crazy about.

I just re-read your post and noticed the air pump stuff.

THERE IS NO EGR. There is no hose to the intake manifold. If you have the hoses exposed, then the solenoid is likely opening when the air pump is supposed to be running and dumping exhaust right into the engine bay. You need to cap all the hoses off or get block off plates.
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Old 03-22-2013, 02:42 PM   #9
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Quote:
Originally Posted by Maxwell Power View Post
It's likely not a leak.

On cold start, the ecu runs ignition timing at 5 degrees AFTER TDC and it makes the exhaust very tinny and loud. Sounds like a leak. Then, depending on temperature it restores the timing to normal values (around 17* Before TDC) about 10-60 seconds after start. This is done to fire up the catalytic converter and minimize cold start emissions that the EPA is so retardedly crazy about.

I just re-read your post and noticed the air pump stuff.

THERE IS NO EGR. There is no hose to the intake manifold. If you have the hoses exposed, then the solenoid is likely opening when the air pump is supposed to be running and dumping exhaust right into the engine bay. You need to cap all the hoses off or get block off plates.
To be clear, there is no noise at all. This entire issue is based off of smell, and I never hear any unusual noises.

I made a mistake - I have done the purge control solenoid delete. (which I believe is EVAP, not EGR) On the 07 STI, there is only 1 nipple on the intake manifold, and this has been capped off. I have also capped off the nipple on my turbo inlet. The line near the firewall that brings the gas tank fumes to the intake manifold is venting to atmosphere now, but its routed to under the car. (near the driver side front control arm rear mount) However I would expect those fumes to smell like gas - not exhaust.

The factory 07 STI air pump has been deleted as well. My driver side head has block-off plates.


At this point I'm wondering if the turbo to UP flange is warped. :/
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Old 03-22-2013, 04:15 PM   #10
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ah, well that makes a bit more sense.

Usually if you have an up pipe leak, you'll hear a high pitched shrill tone when you get into boost.
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Old 04-02-2013, 02:09 AM   #11
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So I tried Seafoam. I think I saw some smoke, but I honestly couldn't tell because it was too windy out. This was 1-2 weeks ago. I plan on trying again tomorrow. I also tried using a mirror to see if it would fog up - no luck there.

I started the car again tonight when cold and felt around the turbo area - I didn't feel any air hissing out. I also sprayed some Simple Green on my UP > Manifold flanges - I noticed some *light* bubbling, but it seemed to get slower and slower as the pipes got hotter - thus I think even if this was a leak, I don't think it's the source of my issue. I also noticed that my 2x thick gasket is pinched on the ends, and there's a very small gap towards the middle. I searched around and it seems this is a common issue, and according to Grimmspeed, this does NOT mean flanges are warped. For reference I have a Grimmspeed uppipe, and an Invidia Race header.

I've also noticed exhaust smell even when sitting in traffic now after the car is fully hot, so it's no longer limited to cold start only. After going back through my posts and notes, it seems the whole debacle started when I pulled/lifted the turbo up to fix/tighten the passenger side intercooler bracket. I'm wondering if that turbo > UP gakset is no longer good. I have a brand new OEM gasket ready to go, so I'm planning to swap this in if I have time this week - though I would like to try SeaFoam again first before tearing things apart.

I found this picture on here, which is similar to my issue:

Last edited by Acejam2k; 04-02-2013 at 10:45 AM.
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Old 04-02-2013, 12:55 PM   #12
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I tried an old 2x thick gasket I had laying around at the manifold/UP connection and it still smells - I don't think it's the lower gasket anymore because this gasket made a practically perfect seal.
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Old 04-02-2013, 01:16 PM   #13
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What headers do you have? If they have a slip joint its not uncommon for them to leak when cold until they heat up and expand.
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Old 04-02-2013, 01:27 PM   #14
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What headers do you have? If they have a slip joint its not uncommon for them to leak when cold until they heat up and expand.
Invidia EL Race. No slip joints.
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Old 04-02-2013, 08:10 PM   #15
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I just seafoamed the car with a buddy of mine. It looks like my Grimmspeed uppipe has a leak at the flex joint. When the car was revved, it was spewing smoke from the flex area. Unfortunately after checking with Grimmspeed, they cannot warranty it as I don't have an order number since I bought it brand new from a private party. The car still drives great and pulls which is the strange thing - and I don't hear any extra noise, but it smells bad.

Now the question is - do I pickup a new Grimmspeed uppipe with flex joint, or should I just go with a solid Invidia UP? I don't think changing an uppipe will throw off my tune. The Invidia seems popular, but I know the early (2005-2006) models had some cracking issues at the flanges, which seems to be fixed now.
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Old 04-02-2013, 08:54 PM   #16
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I'd go solid w/o flex. I've seen more flex joints fail than up pipes crack.
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Old 04-03-2013, 12:51 AM   #17
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With the 2x thickness gaskets I have noticed it is very easy to over tighten, causing the flanges to bow like the pic you posted. I would simply go back through and torque every flange to factory specs, or to where they are tight but not gorilla tight to avoid tweaking your flanges.
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Old 04-03-2013, 01:03 AM   #18
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Originally Posted by 2gnt2wrx View Post
With the 2x thickness gaskets I have noticed it is very easy to over tighten, causing the flanges to bow like the pic you posted. I would simply go back through and torque every flange to factory specs, or to where they are tight but not gorilla tight to avoid tweaking your flanges.
See my post above. My Grimmspeed uppipe has a failed flex joint.
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Old 04-19-2013, 01:25 AM   #19
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The problem appears to be fixed now. The issue was a cracked flex joint on my Grimmspeed uppipe. I removed the Grimmspeed pipe, and swapped in a brand new Invidia uppipe. I went with the Invidia because I already had the Invidia EL Race header. Even though this pipe is now solid, the fitment is absolutely perfect and even better than the Grimmspeed. There is definitely something to be said about using parts from the same manufacturer.
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Old 04-19-2013, 08:34 PM   #20
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Did u contact grimmspeed? They are awesome guys and would warranty that out I bet.
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Old 04-19-2013, 08:40 PM   #21
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Did u contact grimmspeed? They are awesome guys and would warranty that out I bet.
Of course I did. I bought the pipe when it was brand new, but I was technically the second owner - therefore the warranty does not apply to me. (I bought it via private party)
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Old 04-19-2013, 11:56 PM   #22
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You should have Subaru exhaust gaskets ready for when those crappy multi thickness gaskets start to leak. They frequently do. So many questionable products.
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Old 04-20-2013, 12:04 AM   #23
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You should have Subaru exhaust gaskets ready for when those crappy multi thickness gaskets start to leak. They frequently do. So many questionable products.
Never had a problem with the 2x thick gaskets leaking. I have run them on my car for 60k+ miles. (Multiple ones that is, never blown one)
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Old 06-28-2013, 04:32 PM   #24
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Check the welds for the various mounts. my DP had a small leak (but getting progressively worse) that i could smell and hear. none of the gaskets were the problem. finally, it got big enough where i could pinpoint it by ear - the welds on the hanger bracket that attaches near the tranny had over-penetrated, and it was ripping away a nice rectangular piece of down pipe. I was able to jb-weld it, but it eventually let go anyways. Then I bought a new one, lol
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Old 06-29-2013, 06:54 PM   #25
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My Invidia uppipe has been working out great so far - no more leaks!

I see that I didn't update this thread with pictures of my failed Grimmspeed uppipe. I simply cut away the braided area of the flex joint, and this is what I found:





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