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Old 09-28-2012, 01:08 PM   #1
.redshift
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Default These exhaust leaks are killing me...

OK, some background. Picked up a 2002 WRX Wagon a couple of weeks ago. It looked nice and clean, unmodified, and just a few miles shy of 100,000. The struts were blown beyond recognition and it had what sounded like a minor exhaust leak in the front, but otherwise it seemed mechanically sound so we went ahead and bought it.

Fast forward a weekend or two and I finally have it on stands and can give it a proper inspection. The car spent the first 8 years of it's life in NY so it's nice and rusty underneath. The heat shields have almost completely biodegraded, but underneath the shields, the manifolds and crosspipe actually look pretty clean. I verified that exhaust was pooting out between the joints, so I ordered some replacement gaskets and figured that would fix it.

Now that I've gotten it all apart and replaced the gaskets, it is still leaking! I replaced both manifold-to-head gaskets, both manifold-to-crosspipe gaskets, and the manifold-to-uppipe gasket. I torqued the bolts/nuts per the factory service manual (don't remember exactly, but IIRC it was somewhere around 20 ft/lb), and I still have leaks at the right manifold/crosspipe and right manifold/uppipe joints. I tightened them more, but still leaking right out the side between the flanges.

I used thick grimmspeed gaskets, so I don't think the gaskets are to blame, and I doubt that the flanges could be bent as they're pretty stout. Is there a better way, or some sort of gasket sealant I can use in addition? I wouldn't worry about it if it was just noisy, but the idle is kind of wonky and the car feels like it is "fluttering" while accelerating at moderate throttle and I think the pre-turbo exhaust leaks could be causing that.

Any tips on how to get those joints sealed up? Also, are the heat shields on this car necessary to protect adjacent parts, or can they be safely left off? Mine had to be mostly destroyed to remove so I'd be looking at buying replacements or doing some kind of header wrap if it were absolutely necessary I suppose.
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Old 09-28-2012, 01:16 PM   #2
NFJ79
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It's safe to run with the heat shields off. As far as the exhaust leak, maybe there's a crack.
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Old 09-28-2012, 01:21 PM   #3
.redshift
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Quote:
Originally Posted by NFJ79 View Post
It's safe to run with the heat shields off.
Good. After putting it back together, the one on the crosspipe rattles like hell at 3,000 rpm now that half of it's fasteners have turned back to iron ore.

Quote:
Originally Posted by NFJ79 View Post
As far as the exhaust leak, maybe there's a crack.
That's what I was thinking, but I went over the manifolds and crosspipe like crazy searching for cracks or breaks. I don't feel anything coming out except between the flanges. I suppose there could be a crack higher in the uppipe and the exhaust is just getting trapped in the heat shield and coming out at the bottom, fooling me into thinking it is coming out the flange. I haven't taken the uppipe off yet. I'm changing motor mounts soon so I guess I'll do that at the same time.
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Old 09-28-2012, 01:25 PM   #4
BBarnes1
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Check the flanges with a straight edge. Mine were warped. You'll also probably have to play around with the torque order. Theres different theories as to whats best, here is what worked for me:

Crosspipe to collectors
Collector to up pipe
Collectors to head

Also 26 ftlbs usually doesn't cut it, try 30, and retorque after a few heat cycles
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Old 09-28-2012, 01:29 PM   #5
NFJ79
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Quote:
Originally Posted by BBarnes1 View Post
Check the flanges with a straight edge. Mine were warped. You'll also probably have to play around with the torque order. Theres different theories as to whats best, here is what worked for me:

Crosspipe to collectors
Collector to up pipe
Collectors to head

Also 26 ftlbs usually doesn't cut it, try 30, and retorque after a few heat cycles
^^what he said!
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Old 09-28-2012, 01:39 PM   #6
.redshift
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Default

I did not think to check them with a straightedge. Good idea, I'll do that tomorrow. I drove it to work today, so it'll have a few heat/cool cycles before I get it back on stands tomorrow for oil change, etc. I'll retorque those bolts.

If the flanges are indeed warped, will doubling up gaskets help or should I just look into a new exhaust anyway? Everything that I can see from the downpipe back is also pretty nasty. I don't know if this car was ever maintained by the previous owner beyond oil changes and fuel fillups. I have a receipt from when they took it to a dealership to get the wipers replaced in like 2004.
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Old 09-28-2012, 02:23 PM   #7
hudsonvalleybugeye
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Grimmspeed sells 2x thicker gaskets, also maybe some copper gasket sealant. Aside from that, new/used parts. Good luck
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Old 09-28-2012, 02:36 PM   #8
.redshift
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I was wondering about the gasket sealant -- specifically would the high temps of an exhaust manifold just obliterate it?
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Old 09-28-2012, 03:00 PM   #9
hudsonvalleybugeye
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Not 100% sure, I know they make them for all kinds of temps.
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Old 10-01-2012, 04:08 AM   #10
boostin20
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Assuming you don't have cracks near a weld or really warped flanges, that permatex copper rtv sealant should do the trick. It's the highest heat range, and I use it for all flange gaskets at work.
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Old 10-01-2012, 10:12 AM   #11
tebriel
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yeah I have a leak on my manifold to uppipe gasket as well, eventually I'll take it apart and try out the copper rtv.
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Old 10-01-2012, 01:57 PM   #12
classicaddict
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Quote:
Originally Posted by tebriel
yeah I have a leak on my manifold to uppipe gasket as well, eventually I'll take it apart and try out the copper rtv.
I use copper rtv religiously. Not to much, a nice thin bead (1/4inch or so) works perfect. Let it dry for about 5 min before install. Just not to much that it will squeeze out and then be sent into the turbo. There is also a company that makes copper gaskets and I would think they would be superior to any other gasket.

Use some sand paper and clean the flange of any corrosion, I use a die grinder with a roloc "red" disk attached.
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Old 10-01-2012, 03:25 PM   #13
tebriel
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yeah better gasket surface prep would probably save us all a lot of headaches.
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Old 10-01-2012, 05:14 PM   #14
.redshift
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Agreed. I am picking up some of that copper RTV tonight. I scraped the flanges with a razor blade until they were smooth as a machined face, but no dice. Haven't had them apart again to check straightness, but I think they may be warped.
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Old 10-01-2012, 05:19 PM   #15
classicaddict
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Quote:
Originally Posted by .redshift
Agreed. I am picking up some of that copper RTV tonight. I scraped the flanges with a razor blade until they were smooth as a machined face, but no dice. Haven't had them apart again to check straightness, but I think they may be warped.
Doubt they are warped, just a nice layer or rust. It will look smooth, but I promise it's rusted and needs to be smoothed down. Buy a sanding disk for a drill from home depot if you want, but the rtv should help. Lay a bead then spread it with your finger.
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