Fuhnominon

Hi everyone,
I recently removed the exhaust to change an exhaust manifold on 2005 4.6L V8 XLT. Now that I've reinstalled the exhaust pipes I am getting codes P0171 and P0174, both banks are running lean according to the sensors. I can also hear leaks at the flanges.
I was wondering how I can actually get thie exhaust pipes to seal off properly at the flanges so it can operate normally ? I was wondering if I'd have to install donut gaskets with the exhaust pipes as maybe they have been warped a bit when initially removing? I'm not sure what to do here so I'm asking any and everyone here who may have experience with this or ideas that I could try?
Thanks in advance for your input!

Johnny Paycheck

I believe Remflex makes gaskets that will fill in warped spots.

Or…nip the warpage in the bud and have a shop get the manis sanded flat and reinstalled. Did that with my Ram about a month ago. Those manis are terrible for warping.

https://catalog.remflex.com/FORD_Hea...ket_p/3019.htm

Fuhnominon

Thank you very, very much for this info. Will give them a try!

Fuhnominon

What can I do for the leaks where the exhaust pipes connect to the manifolds at the flange?

manicmechanic007

Drop the exhaust back down partially.
Tighten it up going back and forth from nut to nut, so the flanges go up evenly
Support the other side of the y pipe while you work on one side and hold it in relative position
Good luck

Fuhnominon

Ok thank you!!

needsmoarturbo

I concur with the suggestion above to just loosen and try to tighten more evenly.
These exhaust collectors don't have a donut gasket like they did in the 60s and 70s, they have a ball shaped flare on the manifold and the end of the pipe is bell shaped so they should meet together pretty nicely if evenly tightened

Fuhnominon

Ah ok I misunderstood what was being. Said to do. I thought I was being told to remove the manifold take to a shop and get the surface that contacts the engine resurfaced. I didn't realise was talking about the ball joint, ok so I'll probably do both the face and also tighten straight and evenly and see what progress is made.

Thanks so much!

needsmoarturbo

Depends on where the leak is. Those flat gaskets are for between the head and the manifold. Ensuring the manifold flanges are flat and planar helps with leaks there.

If your leak is only at the connection between the manifold and pipe then just concentrate efforts on loosing the pipe connections and evenly tightening them again

Fuhnominon

Thank you! Was leaking at both the oval shaped flange and the mating surface between manifold and cylinder block. So I took care of the flanges now have to tackle the gasket at the block...sigh!