No Matter What I Do - Exhaust Manifold Leak

[oscarsnapkin]

I'm pretty much at the end of my rope dealing with an exhaust leak on my '77 2.0L Bus. New heads from Headflow Masters with less than 70 miles on them. Go back to spring when I had a leaking exhaust manifold on the right hand side. I took the manifold off, filed it down nice and flat and it worked great. I put compressed air through the tailpipe to check for leaks and noticed that the driver's side was leaking, even though I couldn't notice it by ear. No problem I thought, I'm an expert now. I took it off, filed it flat, now it was leaking worse, from the rearmost exhaust port (can't remember which cylinder number). I've been working on this off and on now for months, having spent well over $150 on gaskets, copper rings, and even another manifold. I haven't been able to drive my Bus all summer, and winter will be here before we know it and it'll be another year of sitting in the garage. I've filed the manifold ends down as flat as I possibly can. I checked them for flatness both on a piece of glass and with a piece of sturdy metal c-channel. I've probably taken the manifold off and on well over 20 times, each time probably taking close to an hour by time I disconnect the u-pipes, undo the manifold, etc... I just don't know what else to do and can't bear the thought of having to do it again. If the manifold is filed flat, how can it be leaking? I could see maybe one or two times if the gaskets didn't seat properly, but not over and over again. Please help me end my madness.
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- 1977 CEI Sunroof Bus 2.0L F.I. Hydraulic Lifters
- 1973 Thing

"It’s so easy to laugh, it’s so easy to hate, it takes strength to be gentle and kind."

[Randy in Maine]

Did you anneal the copper?

[busdaddy]

When you try it on the heads with no gaskets does it go down (up) into the gasket recesses?, or hang up on the edge?. After all that filing do the ears the studs go through bottom out on the head first?. Checked for a crack down on the F pipe where the front and rear pipes merge? (that sounds lust like a head leak).
And as Randy says, how about the annealing?
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[Wasted youth]

At the risk of sounding like an idiot... because I know you had the heads rebuilt by a competent machinist...

Is it possible the mating surface on the head is actually the culprit, and not the manifold?

[Wildthings]

It is possible that you have a hole in the flange or the joint where the flange is brazed to the pipe and do not have a leak at the gasket.

There is more to getting a good seal at the gasket than having the flanges flat, the mating surface of the flanges needs to be pretty much the same exact shape as a new copper gasket. If the flange is eroded or deformed it will not seal well. Inspect your old gasket to see how the flange sits against it and also look for soot left by the leaking exhaust gases.

[Tcash]

Exhaust install
http://www.thesamba.com/vw/forum/viewtopic.php?p=7271723#7271723

Good luck
Tcash

[oscarsnapkin]

[Wasted youth]

I can only suggest rigging up a low pressure air set up and back pressure your manifold after you torque it down to the head. Then use a small application of soapy water to show you where the leak is. A long tedious pain, but might resolve part of the mystery.

[udidwht]

Use a length of rubber hose to search for exhaust leaks at all the joints and where the manifolds are brazed together at the collars on the flanges themselves. How certain are you the air injection ports are leak free?


You might be in the need of this...

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1972 Westy Hardtop/Type-4 2056cc
96mm Biral AA P/C's~7.8:1CR
Headflow Masters New AMC 42x36mm heads w/Porsche swivel adjusters
71mm Stroke
73 Web Cam w/Web solids
Dual 40mm IDF Webers - LM-2 - 47.5 idles/125 mains/190 air corr./F11 tubes/28mm Vents - Float height 10.45mm/Drop 32mm
Bosch SVDA w/Pertronix module (7.5 initial 28 total @ 3400rpm)
Bosch W8CC plugs
Pertronix Flamethrower 40K coil
S&S 4-1 w/Walker QP 17862
3 rib 002 Trans
185R14 Hankook tires

[skills@eurocarsplus]

this is a good job for a smoke machine. you can buy a cheapie from ebay made from a paint can. you'll use it more than you think
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[nathansnathan]

I had to reweld where the stubs meet the pipes on some type 4 dansk boxes. I noticed they brazed them on in Denmark, and I assumed the stubs are cast iron. I used a tig welder and brazed welded them with silicone bronze. Welding cast iron to steel with steel filler, it is likely to crack again.

+1 on verifiying the seal using air. I use a small tube of aluminum that I have shoved through a large rubber stopper. I put the valves to tdc and check them 1 by 1, blowing through the tube with my mouth, with the stopper held against the heaterbox flanges, muffler off. Dansk boxes are not quite true and it matters what order you torque them in I 've found.

[udidwht]

[SGKent]

$3.99 at HF

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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

[Wildthings]

[1967250s]

Never saw where the leak is from, though you intimate that the leak is at the head. I once had the manifold pipe rust away at the bottom at the heat exchanger ( wish I had kept those to weld). Is it possible that the leak is at the cylinders and head seal?
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'72 Elm Green Deluxe

[Tcash]

At this point. Pictures would be cool.
How to post photos/How to post a photo in the Forums