Thank you for the reply.
I haven`t replied yet because I forgot to make the time to do this fix.
The original diamond shaped egr exhaust manifold gaskets (3 fixes ago) were in extremely bad shape or nearly nonexistent ... then I did the fix and car felt so great right after.
Then the problem came back after a multiple hr continuous highway drive at about 75-85mph.. but I bought new gasketS and did the fix twice again (this was in the past).
Manifold surface is probably too pitted from corrosion to create a good seal even with new gaskets. I also tried a 2-layer stainless version of the same gasket with not much luck. It held for a few months only.
Also, the manifold had a tiny vertical (tight) crack at the very low point at the very center below the mushroom pipe where the two sides of the exh manifold meet. It is on the lower lip of the surface where the gasket goes.
I noticed the same kind of exhaust manifold crack on another d24t engine too, perhaps it is a common thing to ignore such as hairline crack between the valves?
I have no idea but I started to see dark black stains again where the current gasket is not sealing well. And the car doesnt really pick up speed and has a weird high rpm performance... this developed slowly and gradually and no other fixes were done so i am sure it is this exh manifold seal tricking me.
I doubt I have restricted exhaust but I do have high rpm power loss and a very slow turbo spool action. I also noticed that the little square blockoff plate under the turbo has a very seriously corroded tiny set of screws and plate. I bet there`s no gasket inside there anymore, either....that humpy shaped Mercedes Benz Garrett turbo gasket... hard to find btw.
You suggested trying other type of gaskets to see if that would solve it...
For the leaky manifold surface I tried various types of gasket materials, stainless steel and composite too.
Eventually they let the hot fume make its way through. Prior to the 2020/21 Weird Virus Winter I did this fix successfully (messing with broken studs and the typical exhaust pipe joint stud issues as well) and thought (=hoped) I will be happy with it for a good couple of yrs. Wrong.
I was lucky to have time for 15 skiing daytrips to a far away PA ski resort that added about 3500-4000 highway mountain miles and on the last one I felt the car really losing power due to this leak... Left it like that but i`m annoyed a lot by it. First I thought it was all the heavy gear and five passengers, mtn elevation etc but it wasnt that...
Thinking of JB Welding it and simply use my fingers to apply it after wire wheeling that crap instead of removing so many parts and/or dealing with rusty bolts or broken studs again.
The benefit was to be able to add new intake gasket and exhaust manifold gaskets and check on the rear hose behind the head and clean the starter area as well. Other than that, I really want this issue to end. I would be happy if egr hole got welded shut.
I am considering to get another d24t manifold welded shut then `simply` add that right after I get the current one off. But still, it is not my fav project. If jb weld fixed it, i would be ok with the looks.
Hey it worked on diesel injectors before and they are still holding. Hot and transfering diesel fuel, jb weld is holding there strongly (fuel nipples of the injector came loose/out)
Would it be a realistic idea to jb weld under (and between) the gasket and exh manifold surfaces? I think my manifold surface is too badly pitted to create the best seal even if i keep throwing various new gaskets at it. And you also risk killing the stud every time. Especially if you think all it needs is tightening.
I am really into this because it is so damn annoying to drive it like that since even a well set d24t is kind of slow.