Exhaust leak at 2-1 Elbow. OEM gaskets not sealing it. Solved

[Steve M.]

Okay, this is going to be one of my long posts, even though I didn’t expect it to be.

I found out my exhaust system was leaking at the 2-1 Elbow. I didn’t hear any of the usual sounds indicating it was leaking. BTW, one way to hear your leaks is to drive alongside a wall and the noises will be bounced back to you.
Another way is to take a shop vac and shove the hose into the tail pipe and blow into the exhaust. Then spray the flange with soapy water and look for bubbles.

Doing a search on the exhaust gaskets I found out more then one person has a problem with the gaskets sealing so I decided to add this to the fixes for it.

Basically, my 2-1 Elbow had just deteriorated from the inside out along the edges of the ports. I bought new set of pipes, elbow and muffler back then and installed them in 2017 (with the exception of the Catalytic Convertor which was still relatively good.) So I’m curious why this elbow went to crap so fast?

The leak as seen along the edge. You can see where the gasket seals right at the edge of the hole and it's missing in one spot.

Better view of the deterioration along the edges.

So I had another 2-1 Elbow sitting around and you can see the better condition of the ports.

The OEM Gaskets as fitted to the elbow just to show the matching of the airway to the gasket. The gasket seals around that metal ring when you torque down the flanges so they elbow needs a perfectly round hole.

So after wire brushing the surfaces I put the exhaust back together fully confident I had fixed the leak.
Eh…not quite.

I checked it the same way I found it-I shoved a vacuum cleaner up the tail pipe and turned it on. Then sprayed the flanges with soapy water to see if there was any air bubbling out.
Pfft…it looked like a jacuzzi down there!

Take it apart again and looked closer and saw that the aft header pipe flange was poorly welded. The weld was good-it just missed the pipe the flange was attached to! You can also see that the width of the flange at that point was a lot smaller than the rest of the flange.

Took the pipe off and walked over to the guy building airboats to get it welded up to seal it. The weld covered the edge of the pipe so it looked good to me. Even with the flange being narrower I tried it because the alternative was… more work. It worked when I first installed it so hoping it would still work.

Well…it didn’t work. It did seal up better on the outside, but now I was seeing soap bubbles coming out from where the pipe goes into the flange and not the edges. WTH???
When I installed these new I did torque the nuts on the flanges to the spec so that should not be bent. I layed a flat edge of a scale on them and they still looked good, but they were not sealing.

At this point I’ve used up 6 exhaust gaskets out of my spares and what to do because putting another set of gaskets on there wasn’t going to solve it.
What to do to fix this…more welding $$$ and take it to a machine shop $$$ to reface the flange flat?
Yeah, I could have used a belt sanded to try sanding the flanges flat, but I didn’t have one of them either $$$!
I tried doubling up the gaskets to get twice the thickness so the fiber gasket material could fill in the gaps. That did not work this time.

Exploring my options for not spending any more money I had a 2 spare engines with the exhaust pipes still attached. I removed the 2-1 Elbow from one and that would have been a waste of time as the headers were in worse shape on the sealing surface. Elbow was good…go figure???

The other engine has the GoWesty stainless steel exhaust pipes on it. I started to remove those pipes…
It only took 2 days to separate the 2-1 elbow from the header pipes due to rusted bolts in the flanges.

I could have just put a chisel in between the flanges and hammered away after grinding the bolts heads and nuts off, but I did not want to take a chance damaging the flanges either by cutting across the sealing surface or bending the flanges. So Aerokroil and heat and Aerokroil and patience took a little while longer. And drilling out the holes in the flanges back to original size…

While waiting on the penetrating oil to work I ordered better gaskets from Summit Racing that I hoped would seal any more leaks in the flanges.

Remflex Gasket Material to the rescue. 1/8 inch of soft graphite material sandwiched together with a screen of metal in the middle. Good to 3000°
https://www.summitracing.com/parts/RFL-GS16511

Being 1/8 inch thick and soft it is going to fill in any imperfections such as slightly bent flanges from improper torque applied to the nuts and somewhat deteriorated sealing flanges.

It is very soft and a pita to cut out. If you bend it and put a crack or separation in it …start over!
Some folks go nuts trying to cut this stuff, but here is what works for me.

Use your existing gasket to copy the pattern onto the Remflex. Here’s the four gaskets used for the header to cylinder head flanges. Line them up edge to edge because when you do cut them out you will have one less side to cut out. Leave them all together-don’t cut them separate yet.

As I said the graphite is soft so just using a ballpoint pen you can trace the outline of the old gasket onto the Remflex. Then I used a caliper to measure the exhaust hole and some lower math to find out half the diameter of the hole. Then use the caliper to find the center and marking the center just by pushing the caliper into the gasket. Do this from 4 sides of the hole and you can get an accurate center even though you might wind up eyeballing the center closer to center.

Trying to cut a round hole out of this stuff is do-able-it cuts very easy. The problem is keeping it flat while cutting and not missing or using too much force and cutting outside the lines. If you had cut them into separate gaskets to cut the holes there is danger of bending/cracking them. The sheet material is stronger when left as a sheet. So cut all the holes and then separate them in individual gaskets.

The hole for the exhaust I think is about 37mm and you’re not going to find a drill bit that size that would work. You can use a Forstner Bit for woodworking to cut the soft graphite.

This Forstner Bit was 34mm and under sized, but that works out okay. The old ghosts that have ported out a set of cylinder heads for racing cars are rolling over in their graves right now! These VW header pipes… there’re not made for race engines! The inside diameter of the flange is wider then the outside diameter of the exhaust pipe and looking at my pipes the welding done on the inside diameter the weld bead area does not sit flat so there is an area of turbulence at the flange caused by this. The weld bead kinda makes a cone shape for the exhaust gas to flow into the header pipe, but it’s a shit show in terms of airflow. Racing engines the inside diameter of the pipe matches the exhaust port on the cylinder head almost perfectly depending on the skill of the guy doing the custom engine build. It makes a big difference.
I would have been happier with buying the Forstner Bit made by Milwaukee tools because that measures 36mm, but that is more money to spend and I had this one. This actually comes close to the inside diameter of the pipes so it works.

Now there is a metal screen sandwiched in-between the graphite sheets that make up the Remflex gasket material. On this Remflex gasket it is such a soft metal that you can cut it easily with a razor blade.
A Forstner Bit has no problem cutting through it and it also cut a smooth hole even though it makes a mess.

For the bolt holes on the flange I used a hole punch to mark the holes. I did not use it to punch the hole as it would distort the graphite and probably make it un-useable by breaking the graphite apart because the hole is too close to the edge. (This is where leaving the gaskets all on the sheet before cutting the holes helps keep them intact without breaking apart.) I used the correct punch size for the hole diameter to line up the hole letting the center punch in it to mark the center of the hole. Then I just used a drill bit to drill out the bolt hole.

After all the holes are cut then you can use a box cutter to cut out the individual gaskets. That’s easy to do.

The bolt holes in the graphite are not going to be smooth hole because of the drill bit. You will have to trim them to clean them up. You do not want to cut down into the hole, just remove the excess around the edge of the holes as this increases the thickness of the gasket at the holes and you want it to be uniform across the face of the gasket when you tighten it down.
The thickness difference between the oem gasket and the Remflex.

Remflex gives a suggested torque value of 20 Ft. Lbs to compress the gasket.
This is close to the 18 Ft. Lbs. I have in my copy of the Bentley.

It worked and I do not have any more exhaust leaks on my pipes.
I did use the OEM gaskets at the Cylinder head flanges. My reasoning here was that if I add thickness in these gaskets then the other end of the pipes would no longer match the spacing of the 2-1 elbow.

There is a crack in my muffler, but that is after the O2 sensor so that should not be affecting the fuel air ratio.

Sealing my leaks unfortunately has not solved my problem with my poor fuel mileage…Argggh!
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[4Gears4Tires]

That's a lot of work! But I'm glad it worked out. I didn't know they made exhaust gasket sheets, thanks. I am going to order one. I keep a sheet of regular gasket material around because you never know.
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'87 Syncro Ferric Oxyhydroxide Superleggera Edition
'85 Westy Sciuridae Domus Edition

[Steve M.]