Removing threaded exhaust from manifold

[kenbo]

If you haven't already brought the manifold to Hansen I would encourage you to use the hacksaw technique. The only risk is cutting too deep and buggering the female threads.
But not to worry there's no real pressure there so no real threat of exhaust leakage. I've done this on high-pressure steam boilers and it works very well. Leave about 3/8" inch of pipe or fitting exposed outside the female part and cut slowly. I use a naked hacksaw blade wrapped with a rag so as not to exert too much downward cutting pressure. Stop sawing as soon as you just see the female threads. Use a small caping or cold chisel to curl the male threads off.
and you're done.
It's actually quite easy.

[Bycrick]

Before you try a major redesign, maybe it isn’t necessary. I was able to easily unscrew a steel plug from one end of the manifold, and remove the corroded close nipple on the other end. Using a good high-temp anti-seize (nickel-based) has let me remove the various pieces since then without any further problems. Simply replacing the end plates with thicker aluminum ones solved all the problems.

[mbowser]

Originally Posted by kenbo

If you haven't already brought the manifold to Hansen I would encourage you to use the hacksaw technique. The only risk is cutting too deep and buggering the female threads.
But not to worry there's no real pressure there so no real threat of exhaust leakage. I've done this on high-pressure steam boilers and it works very well. Leave about 3/8" inch of pipe or fitting exposed outside the female part and cut slowly. I use a naked hacksaw blade wrapped with a rag so as not to exert too much downward cutting pressure. Stop sawing as soon as you just see the female threads. Use a small caping or cold chisel to curl the male threads off.
and you're done.
It's actually quite easy.

Since i had a few days before I can drop the manifold off, your words encouraged me to try the hacksaw technique. I cut the pipe off about 3/8-1/2" from where it threads into the manifold and then cut the pipe into 4 pieces on the inside (being very careful not to wreck the female threads in the manifold. then I took a cold chisel and attempted to curl the pieces inward and pop them out. All seemed to be going well until the pipe sheared flush with the manifold. To make a long story short, that pipe is essentially part of the manifold and there is no way I'm going to get the pipe out without some tooling at this point. Maybe they were welded in at some point and the exhaust soot was covering up the weld (although I'm not even sure they can be welded together). In any event, I don't think I did any damage and despite my fail, at least I gave it a try. Now I'll take it to Hansen knowing I did everything I could to get the pipe out.

[Bowdrie]

I've done similar.
It's a hard nut to crack, but I learned that it's similar to a sliced pie that has threads around the perimeter.
With four slices you can't wedge the slices closer together enough to get one out, the diameter doesn't go down enough to clear the threads, (at least for me it didn't).
Close-by one of the slices you have to make another one.
Then once the little piece is out now you have the room to collapse inward the four sliced parts.
I gotta say, your job looks harder.

[wyb2]

Originally Posted by mbowser

… All seemed to be going well until the pipe sheared flush with the manifold. To make a long story short, that pipe is essentially part of the manifold and there is no way I'm going to get the pipe out without some tooling at this point…

On the contrary, you are getting close to success and you have 3/4 of the pipe left to work with

As noted above, you are probably trying to remove too large a chunk. Your cuts are 90 degrees apart, I suggest about 30.

Make sure your cuts are deep enough, you should start to see threads. As also noted above, minor damage to the female threads is not going to be a problem.

Aluminum and steel cannot be welded, you are battling corrosion, and it can be impressively strong. An old coworker of mine pulled a stump out of the ground with the ball hitch on his truck with no pin holding it into the receiver. It has rusted itself in there and he couldn’t get it out. He wasn’t trying to pull the stump, he was trying to remove the ball.

[minard_m]

Another Solution would be to remove that heat exchanger and replace it with a Bowman heat exchanger.Look the company up at https://ej-bowman.com/products/marin...ing-solutions/.
The unit bolts directly to the exhaust ports on your engine. This unit is at an entirely new quality level compared to what you are trying to repair.
I have had one installed on my engine for 20 years and it has been trouble free. You will need to work out the input line from the water pump and the discharge line if you have oil coolers.

[lifeofreilly57]

Have you tried heating it? sometimes applying heat to the tapped bung in the manifold will break the corrosion bond enough to allow the piece to unscrew.
My only concern is if the threads in the manifold have corroded as well.
If thats the case it'll be difficult to remove no matter what strategy you use.
I've been able to redo the threads in one manifold that had a threaded exhaust outlet, but had a friend in the heating business who happened to have a pipe thread tap at that time which was big enough. He retired and sold the business so next time it might be cheaper to replace the manifold than to buy the tap.
Otherwise the earlier suggestion to cut the piece off and then cut the th remaining pipe and take it out is the only alternative.
A long time ago in a galaxy far far away I was a millwright, taking apart and repairing old industrial equipment wa part of the job, piping in chemical plants presented similar issues, corrosion was a constant issue. Cutting the fitting flush to the manifold, then using a chisel to deform the remaining piece by knocking it into the center of the pipe, kind of like folding one side into the center would usually do the trick. Trying to cut it length wise is tricky to do without damaging the threads on the manifold.

[Stu Jackson]

Originally Posted by minard_m

Another Solution would be to remove that heat exchanger and replace it with a Bowman heat exchanger.Look the company up at https://ej-bowman.com/products/marin...ing-solutions/.
The unit bolts directly to the exhaust ports on your engine. This unit is at an entirely new quality level compared to what you are trying to repair.
I have had one installed on my engine for 20 years and it has been trouble free. You will need to work out the input line from the water pump and the discharge line if you have oil coolers.

But it's not a HX.

[mbowser]

Originally Posted by minard_m

Another Solution would be to remove that heat exchanger and replace it with a Bowman heat exchanger.Look the company up at https://ej-bowman.com/products/marin...ing-solutions/.
The unit bolts directly to the exhaust ports on your engine. This unit is at an entirely new quality level compared to what you are trying to repair.
I have had one installed on my engine for 20 years and it has been trouble free. You will need to work out the input line from the water pump and the discharge line if you have oil coolers.

Those look lovely. It's hard to tell from the website, do they replace both the heat exchanger and exhaust manifold? I do have a brand new OEM heat exhanger that cost way more than it's worth, I can't imagine what these go for.
What type of engine do you have?

[mbowser]

Originally Posted by lifeofreilly57

Have you tried heating it? sometimes applying heat to the tapped bung in the manifold will break the corrosion bond enough to allow the piece to unscrew.

Yep, I've been applying varying degrees of heat for the past few days. Now that I removed the end plate after cutting off the exhaust pipe, I can apply heat much more evenly.

[minard_m]

Originally Posted by mbowser

Those look lovely. It's hard to tell from the website, do they replace both the heat exchanger and exhaust manifold? I do have a brand new OEM heat exhanger that cost way more than it's worth, I can't imagine what these go for.
What type of engine do you have?

Yes it bolts directly to the exhaust ports and serves as both manifold and heat exchanger. My engine is the Japanese version of a Perkins 4-154.
The original equipment was the Hansen style with a tubular heat exchanger.

[mbowser]

Originally Posted by minard_m

Yes it bolts directly to the exhaust ports and serves as both manifold and heat exchanger. My engine is the Japanese version of a Perkins 4-154.
The original equipment was the Hansen style with a tubular heat exchanger.

I'm intrigued... I see that they make one for the Mitsubishi K4D (the engine block for the W27). Do you recall how much the Bowman cost? I may have to give them a call. Also, do you heat your water off the Bowman (calorifier)?

[pbiJim]

Originally Posted by mbowser

...
I called an EDM machine shop and they only use EDM for broken taps, not 2" steel pipe. They said that the could put it on a mill and probably machine most of it out, but no promises.

EDM comes in 2 flavors. There is wire EDM & electrode EDM. What is being discussed here is electrode EDM. In this case, an electrode is machined to the desired shape & then plunged into the base material while the spark generator is turned on. The arc erodes the base material & forms a hole in the shape of the electrode. The base material can be mounted on a turn table, if you want to make circular undercuts or helical interpolations (threads). The cross sectional area of the electrode is limited by the capacity of the power supply feeding the spark generator. It takes a very big machine to run an electrode that is more than a half inch in diameter.

The grandparent of the EDM was known as a spark eroder. It produced a more crude result, but was able to disintegrate a broken tap. The modern EDM machines can cut complex shapes & leave a finish that only requires minor additional work to remove the undesirable finish.

There are other tricks for removing broken taps. Some involve liquid nitrogen & a punch. Some involve a cone tip acetylene torch & mercury. Some involve a 4-prong tool. Some involve a nut & a tig welder. In some cases, strategic individuals will choose to use carbon steel taps, rather than high speed steel taps, to facilitate removal of broken remnants. In other cases, some people will choose to use roll forming taps, rather than any of the various varieties of "cut taps" in order to avoid the breakage in the first place. I could easily write another 4 or 5 pages on criteria for proper tap selection, but I'll end here because I've probably already written more than was really necessary.

[pbiJim]

Originally Posted by mbowser

...Maybe they were welded in at some point and the exhaust soot was covering up the weld (although I'm not even sure they can be welded together)....

Steel can't be welded directly to aluminum by any process that I know of.

[pbiJim]

Originally Posted by mbowser

I'm intrigued... I see that they make one for the Mitsubishi K4D (the engine block for the W27)....

K4D you say? That got me digging into my scrap pile. Unfortunately, it appears that Westerbeke used a couple of different exhaust manifold configurations on that base block. The one I have here is tall & thin, rather than wide & short, like the one in the picture with your first post. The exhaust connection is very different.

The K3D is the base block for the W21A, which I have. I had bought a sunken K4D for parts a few years ago, because a lot of the parts will transfer over to my motor. I did not know that the K4D was the W27. The motors appear to be almost identical except for a few details like cylinder bore diameter & probably fuel injector sizes.

The K3D was also used by Toro, in some of their commercial lawn care equipment that was sold in the US. Parts from Toro proved no less expensive & items like manifolds seemed to be custom made for Westerbeke. Unlike marine motors with Kubota base blocks, I have not found a good alternate source of spare parts for the Mitsubishi blocks that were used by Westerbeke.