Sheared passenger side Exhaust Manifold Stud

[meeshow]

Think I found my culprit for the lack of awesome MPG (aside from owning a 5.7 and living in Canada in December) - turns out that 1 of the 8 studs that fasten the Manifold to the block has sheared and is leaking. I have dual Magnaflow 3.5" exhaust from the Cat back which make a HELL of a lot of noise, covering up the leak. With the cold weather I think it's gotten worse and caught my attention finally. Manifolds warped, and need a new set of studs installed. Anyone got any ideas how to get this POS out - sheared at the block. No threads to grab onto - thanks guys, happy new years.

[Tbird100636]

Think I found my culprit for the lack of awesome MPG (aside from owning a 5.7 and living in Canada in December) - turns out that 1 of the 8 studs that fasten the Manifold to the block has sheared and is leaking. I have dual Magnaflow 3.5" exhaust from the Cat back which make a HELL of a lot of noise, covering up the leak. With the cold weather I think it's gotten worse and caught my attention finally. Manifolds warped, and need a new set of studs installed. Anyone got any ideas how to get this POS out - sheared at the block. No threads to grab onto - thanks guys, happy new years.
Sheared at the cylinder head you mean??? Usually those exhaust manifold bolts shear off with enough threads left to twist out once you get the manifold off. All of the 4.7L's and 5.7L I've done so far have been this way, and just twist out easy. They loosen over time, then snap off at the bolt head. Should be 4 studs, 4 bolts, and 4 small nuts (for the heat shields) per manifold. If they are loose enough, a pointed punch and hammer sometimes works. You rotate the bolt loose buy hitting it with the punch.

[meeshow]

Ok- so what I previously posted was what the muffler shop told me. 2 hrs to draw out the studs and another 2 to reinstall the new manifold seemed ridiculous to me. $117 in parts, and a grand total of $593. I'm ordering the new manifold and gasket, and studs for all of them. I haven't been under the truck to look at the exhaust system due to the fact theres 2ft of snow out there and another 6 inches of ice. Does the manifold bolt to the exhaust system at a flange or is it welded together. I mean do i have to cut off the old mani or just torch the old bolts? thanks for the quick response.


Cheers

Eric

[meeshow]

TBird? Brakes aren't dragging like you had mentioned in my other thread. I was getting close to an avg of 18MPG in August, but now with the same driving am getting a whopping 9.2 MPG. Would this leak be contributing to the mileage, trucks not tossing any codes...

[Tbird100636]

Ok- so what I previously posted was what the muffler shop told me. 2 hrs to draw out the studs and another 2 to reinstall the new manifold seemed ridiculous to me. $117 in parts, and a grand total of $593. I'm ordering the new manifold and gasket, and studs for all of them. I haven't been under the truck to look at the exhaust system due to the fact theres 2ft of snow out there and another 6 inches of ice. Does the manifold bolt to the exhaust system at a flange or is it welded together. I mean do i have to cut off the old mani or just torch the old bolts? thanks for the quick response.
Cheers

Eric
The stud have intergral nuts on them, and the studs are longer than the bolts, so you can't do the studs in all 8 positions. 4 bolts, 4 studs, 4 nuts for the heat shield, and the gasket. Check the manifold first with a straight edge before ordering it, you may not need it. Like I said before, the bolts loosen, then break. They don't typically warp. The manifolds are connected to the inlet pipes that go to the cats with 2 bolts and 2 nuts with intergral anti-spin flags on each side. You should not have to torch the manifold bolts, just remove using a ratchet and socket. You'll have to do this under the truck, more room to get at the bolts. The bolts for the manifolds to cats should come apart, they are better than the older style that always required torching, soak with penetraiting oil ahead of time.


TBird? Brakes aren't dragging like you had mentioned in my other thread. I was getting close to an avg of 18MPG in August, but now with the same driving am getting a whopping 9.2 MPG. Would this leak be contributing to the mileage, trucks not tossing any codes...
It is possible. The exhaust just doesn't leak out. The pulses draws in miniscule amounts of air, which does have an affect on the upstream O2 sensor reading, which affects fuel control.

[meeshow]

Basically the stud leaking is causing the upstream O2 to think the engine is running cold all the time right? That's my understanding. So it's running rich? Or lean?

[OsO]

Basically the stud leaking is causing the upstream O2 to think the engine is running cold all the time right? That's my understanding. So it's running rich? Or lean?
Rich . Glad you found it

[Tbird100636]

Basically the stud leaking is causing the upstream O2 to think the engine is running cold all the time right? That's my understanding. So it's running rich? Or lean?
It makes it think it's running lean, and tries to compensate by adding more fuel, making it richer than it should be. Hence, the decrease in fuel economy.

[Deez Nutz]

If you haven't gottten it out yet, there's this thing called gator grip and it's supposed to be pretty good costs like $20 or something