I've had an annoying exhaust leak for some time. I finally decided to do the reverse vacuum in the tailpipe and spray the exhaust down with soapy water. The culprits appear to be the gaskets between the exhaust manifolds and the Y-pipe. Is there a better aftermarket gasket for this area or is OEM the way to go? Thanks.

 

People use Red HIgh Temp RTV between the gaskets to help seal things up.

 

I tried the RTV and it worked... for ~300 miles (albeit, with a pretty bad leak). The problem is there's positive pressure that wants to push out the RTV. It could work., but that depends on how bad it is. I used to double up the gaskets if the exhaust was warped. Another thing that could happen is the nuts backing off. Although, if that did happen, replace the studs and nuts. No matter where you live there's a 90% chance one or more of the studs will break. My D2 has lived its entire life in CA and I broke 4/6 studs.

The "best" solution would be to replace the gasket and replace the studs + nuts.

If you do decide to replace the gaskets and or separate the y pipe from the manifold, spray the nuts/studs with PB plaster. Once in the morning, once at night 3 days before you attempt the job. Extinct has replacements for the exhaust studs better studs with copper. nuts. https://extinctmotorsports.com/exhaust-studs

 

I have used these with some success: https://a.co/d/96aMGtR

 

First off I'd try to double gaskets. If that fails the next step would be.

Remove manifolds and Y pipes.

Remove studs from manifold.

Hunt down a smooth cinder block. Buy one if necessary

Put enough dish soap and water to cover the cinder block.

Now rub the mating surfaces as evenly as possible across the block. Apply water as needed. Do so until you get an even finish.
​​​​​​Now all the mating surfaces are smooth, true. and one metal gasket will seal it properly.

We've trued up air cooled cylinder heads like this for decades.

If the manifold studs are original you're past due for new studs anyway.





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FWIW, I guess I got lucky when I replaced that gasket on Bank 2 eight years ago.

The nuts came off pretty easily, and none of the three studs broke on removal or reassembly. Remember, the torque spec is only 22 lbf.ft. I used a single, stock gasket, probably from AutoZone or Advance Auto, and all is well.

 

I have an exhaust leak in the same place, but am also getting lean codes for both banks, a rough idle and stalling when put into gear. Did this happen do you as well, or is there something else wrong with my car?

 

You have something else wrong. I've run open headers with none of your issues. I have all sorts of exhaust leaks and truck runs fine aside from the noise from said leaks...O2 sensors are not required either for a d2 to run well enough to not stall or cause lean codes.