ARH header leaking at manifold
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ARH header leaking at manifold
2005 M6 102k miles, LS2, cam, upgraded pushrods/lifters, stock heads, ARH 1 7/8" w/ cats
I'm pretty sure I have a leak at the manifold because the car seems like it's down on power above 4k and I hear a faint ticking noise. The valvetrain is pretty loud, but it's a different sound than the "sewing machine". No CELs, and the plug wires looked like they were in good condition when I put them back on.
I just removed the passenger header to replace the starter and reused the gasket that was on there. I torqued the header to the manifold prior to tightening the header to the x-pipe, which upon re-reading the AR instructions I should have tightened the ball joint prior to torque the manifold. The gasket looked pretty new.
The butt dyno says it's down25%+ on power, specifically in the upper rpm range above 4k. Instead of continuing to pull it feels like it falls on its face. Is this typical of an exhaust leak at the manifold?
Are OEM gaskets still recommended?
I'm pretty sure I have a leak at the manifold because the car seems like it's down on power above 4k and I hear a faint ticking noise. The valvetrain is pretty loud, but it's a different sound than the "sewing machine". No CELs, and the plug wires looked like they were in good condition when I put them back on.
I just removed the passenger header to replace the starter and reused the gasket that was on there. I torqued the header to the manifold prior to tightening the header to the x-pipe, which upon re-reading the AR instructions I should have tightened the ball joint prior to torque the manifold. The gasket looked pretty new.
The butt dyno says it's down
Are OEM gaskets still recommended?
Last edited by neverstop90; Jul 29, 2022 at 11:40 AM.
Drifting
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I've reused exhaust gaskets before so I really don't see an issue there. Issue is likely with bolt sequence like you said but either way, no way your losing 25% hp imo. Fix seems easy enough anyway.
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Leaking exhaust manifold / header flange gaskets won't decrease enough HP that you would ever feel it.
If your down on power, you have something else going on with your engine.
If your down on power, you have something else going on with your engine.
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it's a pretty significant leak pretty much across the entire gasket based on pressurizing the exhaust system and using soapy waterjust to confirm, on the gasket the side that is stamped "manifold" is supposed to go toward the headers correct?
This is what the manifold looks like; looks pretty clean as this is the part that had the most build-up. I tried removing the little build up on there, but it isn't coming off. (it's not resting on the spark-plugs; I have it supported below with a jack)
Last edited by neverstop90; Jul 29, 2022 at 11:53 AM.
Burning Brakes
Joined: Oct 2015
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If you are leaking at the header to head gasket, you should be able to see exhaust soot buildup where the leak is. Do you have Cats, if so my first thought is a clogged cat, not a leaking header gasket.
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Put a new gasket on, followed ARHs instructions, torqued 11 then 18 ftlbs center out. Still seeing bubbles at the manifold when i pressurize the exhaust.
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Le Mans Master
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Well, ruled out that the engine head mating surface is clean, level, and not gouged.
Ruled out that the header mounting surface is straight and level.
Ruled out not a pinhole or faulty well in the header.
Used a new gasket with proper bolt torque.
Assuming you ruled in that the leak is at the header to head mating surface.
There are exhaust sealants and would be applied to another new gasket, but I would use this as a last resort.
My two-cent comment is that "speed shops" can sell packages of header gasket material.
This material is typically paper-like and thicker than OEM-type gaskets.
One draws/ outlines the gasket shape they desire and cuts it out of the material.
Good luck.
Ruled out that the header mounting surface is straight and level.
Ruled out not a pinhole or faulty well in the header.
Used a new gasket with proper bolt torque.
Assuming you ruled in that the leak is at the header to head mating surface.
There are exhaust sealants and would be applied to another new gasket, but I would use this as a last resort.
My two-cent comment is that "speed shops" can sell packages of header gasket material.
This material is typically paper-like and thicker than OEM-type gaskets.
One draws/ outlines the gasket shape they desire and cuts it out of the material.
Good luck.
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If you didn't remove the sparkplugs and just worked around them, you might have damaged a plug. Easy to do in that scenario. It would have to be a pretty big exhaust leak to be down enough on power to notice it. A big exhaust leak can cause your ox sensors to send bad info to your ECM.
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If you didn't remove the sparkplugs and just worked around them, you might have damaged a plug. Easy to do in that scenario. It would have to be a pretty big exhaust leak to be down enough on power to notice it. A big exhaust leak can cause your ox sensors to send bad info to your ECM.
new dad brain syndrome, but I finally realized I should test the driver side manifold gasket that I didn't remove since the shop installed it while I pressurize the exhaust. I see bubbles, but to a lesser degree. I have the shop vac hooked up to the passenger side exhaust and i'm just turning it on long enough to build pressure in the system. So I would expect pressure to spike slower/hit a lower PSI on the driver side especially if there are any leaks on the passenger side.
Maybe I'm just being overly critical at this point; the vac is one of the big rigid ones. Should I expect zero leaks? Assuming the pressure is capable of opening the exhaust valves it wouldn't be able to open the intake valves; so the crankcase pressure would just increase until it came out of the PCV?
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I'm going to replace the spark plugs (tested wire resistance, they're good still), drive it a couple of days, retorque the bolts, and see where I'm at.
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decided to give it one more go loosening the headers/collector connection and retightening. also replaced all the plugs with ac delco 41-162's. I didn't pressure test it, but on start-up I didn't hear the same sound that I did last time. Power seems to be on par again.
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Don't have a sense for "a big leak" but there were a lot of bubbles. And easy enough to change the plugs; guess I'll just do that to be sure.
new dad brain syndrome, but I finally realized I should test the driver side manifold gasket that I didn't remove since the shop installed it while I pressurize the exhaust. I see bubbles, but to a lesser degree. I have the shop vac hooked up to the passenger side exhaust and i'm just turning it on long enough to build pressure in the system. So I would expect pressure to spike slower/hit a lower PSI on the driver side especially if there are any leaks on the passenger side.
Maybe I'm just being overly critical at this point; the vac is one of the big rigid ones. Should I expect zero leaks? Assuming the pressure is capable of opening the exhaust valves it wouldn't be able to open the intake valves; so the crankcase pressure would just increase until it came out of the PCV?
new dad brain syndrome, but I finally realized I should test the driver side manifold gasket that I didn't remove since the shop installed it while I pressurize the exhaust. I see bubbles, but to a lesser degree. I have the shop vac hooked up to the passenger side exhaust and i'm just turning it on long enough to build pressure in the system. So I would expect pressure to spike slower/hit a lower PSI on the driver side especially if there are any leaks on the passenger side.
Maybe I'm just being overly critical at this point; the vac is one of the big rigid ones. Should I expect zero leaks? Assuming the pressure is capable of opening the exhaust valves it wouldn't be able to open the intake valves; so the crankcase pressure would just increase until it came out of the PCV?
