APN manifold to downpipe seal leak

I am about to replace my exhaust manifold with a second APN header. (Previous one cracked after about a year. Free replacement though with the lifetime warranty).

Anyways, no matter what I do, I cannot get the flange gasket to seal correctly. It appears that the manifold to downpipe does not exactly line up correctly. The exhaust manifold fits into the downpipe at a slight angle. When looking at the manifold to downpipe connection it appears that it does not seat evenly. If looking from below the Jeep up, lying on your back with your head facing the front of the Jeep, there appears to be more of a gap on the left side (engine side) of where the two meet. Basically, the manifold pipe does not fit flush with the top of the downpipe. I can easily see this when the downpipe bracket is moved out of the way, you know, where you can slide it down the downpipe and it gets stuck between the pipe itself and the oil pan. Is it suppose to seal at an angle?

I have tightened each bolt one rotation at a time to specs (VERY time consuming) in order to get it to seal evenly. Still leaks as I can hear the exhaust leak at cold idle and under load going up hills. I even tried some copper sealant on the donut to no avail. Any other ideas on how to seal this darn thing.

On a side note, I noticed that even with a OEM replacement manifold with the "accordion baffles" to reduce breakage, it did not line up that well either to the downpipe and leaked.

Any ideas??? Anyone with an APN manifold get theirs to seal correctly at the downpipe??

Have you considered adding in one of the flexible stainless sections like Summit sells? When I redo my exhaust, I want to fit one of those in to relieve the stress that seems inherent in our exhausts.

have you tried loosening the other end of the down pipe where is connects to the cat? you need to be able move/twist/bend the downpipe a bit.

when i replaced the exhaust on my 89 from the exhaust manifold back, i left all the connection loose until i got a good fit then tightened them down. becuase of the many angles/bends of the downpipe, you need to have it so you can move it around.

IMHO, stock motor mounts allow the engine to move too much. movement of the engine will crack the exhaust manifold.

89xj said:

have you tried loosening the other end of the down pipe where is connects to the cat? you need to be able move/twist/bend the downpipe a bit.

when i replaced the exhaust on my 89 from the exhaust manifold back, i left all the connection loose until i got a good fit then tightened them down. becuase of the many angles/bends of the downpipe, you need to have it so you can move it around.

IMHO, stock motor mounts allow the engine to move too much. movement of the engine will crack the exhaust manifold.

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That's a good idea. I will try to loosen it at the cat and wrestle with it. Thanks

x2 on the mounts, including the TC/Trans mount.