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Originally Posted by ngoma

Maybe the hairline crack you mentioned is expanding at operating temp.?
As long as you are struggling with this, disassembling/reassembling, etc., why not do this:
EGR Blockoff Plates

Hi Ngoma,
your link shows a nice repair that I also did, approximately a year and a half ago, that was the actual `egr delete job` when that mushroom shaped pipe got cut off and removed then I fought the two studs out of the manifold.

I installed new VW studs in there and I made two aluminium plates to block the two holes. That time I used the high heat version of some red/orange color gasket maker and hoped for a good seal. I roughly cleaned mating surfaces (manifold was very pitted), added a new composite gasket for the upper hole at the intake and used a stainless steel double layer gasket for the hole at the manifold.

The upper one held fine until now and only once had a tiny leak that showed a dark dot of stain.. One of the nuts was later found being a little loose.
I think that happened because I was too concerned about the intake manifold threads (at time of initial installation...). Tightening it a few months later worked well and it has not leaked since.

The `lower` plate, at the exhaust manifold, started showing leaks after those multiple highway high RPM trips. I was afraid to overtighten the nuts so I left it as is but the car really felt that leak (of smoke) and lost quite some `power`. `Roadside` tightening did not help it actually.
One of my new exhaust manifold studs lost some good thread at the time of installation, so I did not want to force tightening nuts too much. At home I shimmed it up using larger washers to use the outermost part of the threads.

The cause of the leak (obviously) is heat itself... it managed to warp the plate I made. I know now, that it was too thin of an aluminum piece to be used for this purpose... its thickness is only about 1/4inch (6mm).




Today I removed the block-off plate from the exhaust manifold
and started cleaning its deeply pitted surface.

Corrosion made its way down into the cast iron really well. The old metal gasket also left the mark of its own shape `carved` into the surface of the manifold.
I used sandpaper to try removing as much materaial as possible, in a mad attempt to recreate a flat surface as much as it was possible, without taking stuff apart, without removing the manifold(s), without power tools, without making the car non-drivable tomorrow.

I also noticed that the plate I removed had a curve or was slightly bent, it was not completely flat anymore so I had to get it cleaned and make/sand it more flat.
I decided to do it the quick way, just to get it done without being involved too much.

The double layer metal gasket was found in fully reusable condition but in the end I decided to use no gasket at all. This may be a mistake, I`ll hear your opinion about it.
It seemed that that gasket had a `bumpy ring` on its surface (at center) and that ring would be working against the totally flat seal of the surfaces.


We`ll see. So I cleaned it all off and used `exhaust cement` between the manifold and the blockoff plate. I think it is rated for 950F (*only).
I regret not buying the high heat JB WELD 2400F manifold paste because that would have been a better choice, I`m sure.



Do you think the exhaust cement can cause problems IF tiny particles end up going in/falling in?

Looking back at my repair today, I recall that I used the cement on the entire surface of the inside of the blockoff plate so there will be a layer of cement where the `hole` is.
If that cement falls off, or burns off and falls, can that be an issue there or anywhere?

If you say yes, I will not use the car like this and I will go ahead and will buy the 2400F paste... and not cover with adhesive the entire block off plate surface on the inside.

The cement sealed really well, protruded when I tightened the nuts and `dried` in 30 mins then I ran the car to warm it all up to sped the rest of the curing up a lot (we had a rainstorm after i took car apart).

Ngoma your plates look very thick, they are double the thickness of my choice... If today`s repair won`t hold, I`ll get thick plates and the Extreme Heat JB WELD sealant. DID YOU USE ANY GASKETS IN YOUR FIX (at the manifold)??



About the crack.
I have this crack on the very bottom of the exhaust manifold where the two sides meet, right in the exact center (lower lip).

As you suggested, it is highly likely that the crack is able to expand although it is super thick material there and the shape of the design hopefully wouldn`t let major expansion happen. Also, it sits really well on its base and four large nuts hold it all together from the bottom.

Are these manifolds easy to weld? I may grab it from the other engine and get it welded (also cracked at the same spot) then get it refinished to completely flat then I could forget this issue for a while. But I am totally not ready to do removals of both manifolds on both engines then assemble them both, twice.



Main news, lol:

I ran a check on how tight my 12 exhaust manifold nuts were.
We all know that there is one at a bad spot AND it`s a bad angle, AND there are 2 more nuts at an even worse spot and an even worse angle...

So, all 3 of those were not exactly as tight as you would want them to be. I tightened them. This I think will help with the power loss symptoms I was experiencing while driving, IDK yet. (Finding them was just the benefit of dealing with the block-off plate issue)
I think the 3 nuts were not tight enough because at the time of torquing the 12 nuts these were the 3 spots where the torque wrench did not fit, so I had to tighten them to specs by `feel`... I probably was overly concerned of overtightening Also the exhaust manifold was installed with brand new gaskets at the time, that could be a factor.

Test drive tomorrow...