Exhaust flange won't seal

I've been struggling with getting a good seal at the exhaust flange that is found between the y-pipe and flex pipe of my '96 Windstar.

The flange leaks at the top and bottom, the areas that are 90 degrees offset from the bolts, and are the most narrow parts of the flange.

The flange is "cupped" so that the it makes contact at the bolt holes before making contact at the pipe. I tried using two exhaust gaskets to get the seal. That didn't work.

Alternatively I tried to correct the cup with a hand file & small grinding wheel, but this is slow work to rub that down. I've considered using a belt sander, although it might be hard to keep it under control given that the flange on the flex pipe isn't held securely.

I suppose it would be corrected with a new flex pipe, but at $200 it is an expense I'd like to avoid.

Any suggestions are welcome.

well, 2 thoughts. 1) I think the flex pipe could be had for $75 from an online source, I know that for my 2000 they are. 2) you could try some muffler cement. I'm not a big fan of this stuff personally but it may act to seal that area. As an aside, I have a natural gas tube heater in my garage. When I installed it, the gas fitter instructed me to use muffler cement at each joint, to seal them. I did as he instructed but recently had to separate them for some maintenance. Man were those joints hard to break! The cement was really strong, not crumbly or weak. So, I kind of have some new respect for this 'quick fix' in a tube. I think the trick is that once you've applied the cement, the muffler (or tube heater in my case) has to be brought up to temperature, and held there for 15 min or so. That cures the cement.

fwiw, my 2 cents

Here's how I handled it. I couldn't see buying a new flex pipe, even if I could find it for $75. I had tried two gaskets but that still leaked, so I took the second gasket, turned it 90 degrees so that the screw holes were sticking out from under the flange at the top and bottom. Once that was tighten down it sealed perfectly.