Exhaust Repair

[Manfreds78bay]

So just finish up a top end rebuild on a 78 FI 2.0l. She runs great. But when removing all my exhaust bits I noticed the joints at the elbows and heat exchangers were extremely warped. I tried to use some high temp silicone, but it was a complete failure.

While I did file down the headers and flanges that bolt to the head, I did not soften the copper gaskets. Can I use a standard propane torch to heat the gaskets to 900 degrees? I plan to do this as well as drill out the header mounting holes.

My question is what should I use to flatten these warped joints? Do you think a exhaust shop could fix them for me? They are pretty bad and I'm not sure if its possible to get them flat enough without removing too much material. Should I use a grinder or sander if I do it myself? And what is a good tool to measure how flat and square they are?

any suggestions would be great. Or if you have had the same issues and how you fixed it..would be helpful.

I have read through a lot of posts, but no one has stated the tools and methods they used.

[SGKent]

I would look for a set that aren't as warped. BusDaddy suggested jacking the F-pipe flanges apart to line the holes up again. I drilled ours as they were just a little off. Also you want to use a propane torch to get those copper rings hot then quench them. You will know if you did it right because they will thud instead of ring when you drop them. You can heat the flanges on the heat exchangers with a torch and whack them a little with a ball peen hammer to straigten them. Scott at German supply has replacement flanges, he also has pieces that have been repaired on a jig.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[RocketRod]

Use a torch with MAP gas. Gets hotter. There is a good article over on Ratwell that will guide you on the F pipes. All metal working takes some time. For straightening flanges heat and vise flat area or body dollies work good. Once you get the manifold on the header, assemble everything else loose and then tighten it down in a connection sequence from the head manifold out. Works for me every time.
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Why Yes it is a Magic bus!
Common Sense isn't so common.

[busdaddy]

All good suggestions, I've had a few that required some major tweaking to even get close enough to file or belt sand across the flanges, had to spread the pipes as SG mentioned and even twist one with a large pipe wrench to get the stud holes lined up. Big vice, big tools required, propane's fine for the copper rings.
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[drober23]

The warped parts you mention are the ones between the exhaust manifold and the "U" tubes? These get warped up but can be hammered back into shape as mentioned above.

I did this recently, and just a few minutes of work made a world of difference in how it went together.

Good luck!
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DJ

'75 Westfalia, '79 Deluxe, and some others...
(more busses than sense)

In a time of chimpanzees I was a monkey

[onion456]

after getting them roughly straight with a hammer or vise or whatever you decide to use, you can then get them really flat with a belt sander. ive done this with excellent results. its very easy to tell when its 'flat enough' as the belt sander will take material from the entire flange rather than just the high spots.

i also like to use that copper exhaust sealant goop on all my connections; some folks dont, but i have had good results with it and i dont like putting it together more than once =)

nice flat flanges, good thick gaskets, copper goop on both sides, sock it up tight with new hardware.. you will have no leaks.
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'76 Sage Green Westy 2.0 FI
'76 Creamsicle 7-passenger 2.0 CS FI
'85 Tan Westy

[Manfreds78bay]

[SGKent]

I filed mine with a long file from 4 different directions one stroke each then lay 400 wet and dry on a piece of thick glass then did figure 8's with it and then reversed it 180 degrees and did figure 8's again. When it was shiny all the way across I went to 600 grit then 1200 grit then 2000 grit - all wet and dry papers on glass. Then I heated the copper to soften it, cooled it and also used a little high temp sealer on it. The studs were all new and I put anti-seize on the special nuts. Last I torqued it in 3 or 4 different stages in a cross pattern and then retorqued it a few hours later. So far it has been quiet.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Manfreds78bay]

[drober23]

SGKent is talking about the mating surface between the exhaust manifold and the cylinder heads. This surface needs to be pretty darn flat. Maybe not as flat as a Japanese Tea Ceremony would get it, but very flat!

Onion is talking about the joints between the triangle flanges on the manifold, U tubes and heater boxes. A belt sander's tolerance is more than sufficient here.
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DJ

'75 Westfalia, '79 Deluxe, and some others...
(more busses than sense)

In a time of chimpanzees I was a monkey

[bajafreaks]

Scott from German supply reconditions exhaust manifolds (f pipes) he did mine and did a great job...he will take a while thats for sure so if you are in a hurry do it yourself per ratwell.

[Manfreds78bay]

I did a pressure test and found out a seam in on of my J pipes is bad. I was leaking all kind of air. It's the flange piece that bolts directly to the heads. Its just under there.

So I called around a found a guy that would weld it back up and put new flanges on the elbow pipes and the J pipe. That should do the trick.

I also heated up my exhaust gaskets. they don't make a ping sound when I drop them, so I think I did it correctly.

I hope the guy can get it done in a day as I'm going on a trip this coming weekend.

Wish me luck.

[Manfreds78bay]

Mechanic was worthless. I take off work early and rush to get there before 6pm and this guy tells me he doesn't know aircooled engines. And didn't even know VW made air cooled engines.

So my next fix will be with JB weld. Has anyone have any luck using it on F pipes. I'm just plugging a whole and no welding parts together. Think it will work on an exhaust?

My plan is to test it with my shop vac and test it with a torch to see if it can stand the heat. Sound good?

Also, are F pipes interchangeable? I saw a classified ad that specifically called out a drive side and a passenger side f pipe. How can you tell the difference?

[bajafreaks]

[SGKent]

jb weld will not hold. You have 1100F+ degree gasses coming out of there. Look for replacements.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[dwill49965]

When my u pipe flanges were warped, I used that cheap exhaust gasket cement stuff from a tube to fill in the gaps. It was a temporary fix that would last a couple of months or so, depending on how many rough logging roads I'd go camping on.

With bus cold, start it up, get under to feel around the u-pipe connections to see where you have to goop the stuff. You'll have 2 or 3 minutes before the exhaust gets too hot. Shut off bus, let exhaust cool a bit - if you've only run it 2 or 3 minutes, it won't take long. Goop the exhaust gasket cement in, mush it into the gap and spread it around the flange connection - and let it sit overnight to harden (if you do this in the evening), and next day it should be sealed up well. Eventually, it will crack and be blown out or fall out. Then do it again - takes 5 minutes, and the tube of cement is about $3 or $4, and will last you for several applications.

Eventually, I got used u pipes with good flanges. Sounds like you may have bigger problems with the seam weld as well though.

This was the gap for my flange:

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Darryl
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'78 Westy, Boston Bob built 2.0 L, FI, MSD 6A

[Manfreds78bay]

I just ordered a new F pipe from Avery's. I bought some exhaust cement and put in on last night. Going to run a pressure test on them tomorrow night. If she passes going to hooker up up and see what happens. I might get the new parts this Friday, so will install if the fix doesn't work.

I hate rushing this, but going on a 2k trip starting this weekend. I just want to get her on the road.

If she blows on the road, I'll just switch out the new pipe.

I'll let you know how it goes before I leave.

[Manfreds78bay]

I reinstalled the exhaust yesterday. I plugged all the wholes I could find with exhaust cement. Or at least that's what It think it is. I comes in a tube and has the consistency of face cream. So far its done a good job so far.

I bought a belt sander and used 80 grit paper on the left side F pipe and elbow joints as they were the worse warped surfaces. It didn't seem like I was doing much or maybe I just didn;t think it would work. I was wrong. Those surfaces bolted up perfectly.

I didn't give the same effort on the right side. I only just resurfaced the mating surfaces. I felt defeated and didn't think it was worth the effort. Next time I have that side off I'm going to give it the same treatment.

I think sanding is the way to go to fixed warped surfaces if you dont have the time to get the new parts.

Thanks for your help guys. I think we can say this was a good fix.

[BusterBrown]

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1978 Sage Green Westfalia (Happy Trails, SOLD)
1977 Transporter

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