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Old 07-13-2022, 03:38 PM
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Exhaust leak

Appologies in advance for the long (but hopefully not rambling) post.

11 years ago, I built a new exhaust hot-section out of 316 Stainless pipe. I spent the extra on stainless so I would hopefully never have to do this again. (https://www.moyermarineforum.com/for...php?albumid=73) Everything except the MMI flange and MMI injection point was SS.

About a month ago, while motoring to a club rendezvous, we left a cabinet door open that connects directly to the engine compartment. An hour later, the Carbon Monoxide alarm went off in the cabin, even though I run the blower whenever the engine is on. Fortunately, we were outside in the cockpit. I closed the cabinet, ventilated the cabin, and finished the trip.

Once back in our home slip, I started to look for the leak. I could definitely smell exhaust in the engine compartment, but was unable to immediately locate the leak without burning myself, and I didn't want to spend much time with my head in there with the CO while the engine was running.

So my next thought was to use an infra-red thermal camera to locate the leak. There are numerous cheap ones available, but I soon discovered that their resolution is a joke (~60 x 60), and usable ones are in the $300 - $400 range. Too much for my budget!

My next approach was to buy a fast-responding digital CO meter. I thought I could probe around with it while the engine was running and look for a spot where it jumped up. The meter showed that, with the cabinet closed and the blower running, the cabin level was zero. The problem came when I brought the meter into the engine compartment. It instantly shot up to over 200 ppm (!) and started sounding an alarm that meant "Get Out Now!"

At this point, I was stumped, so I talked to my mechanic brother who said "Why don't you smoke test it?" He then described a technique that uses a small smoke generator to pump smoke into the exhaust system with the engine off. This way, there is no danger, no heat, and a strong flashlight will reveal the leak easily.

There are numerous plans all over the Internet for building a homebrew smoke generator, but I took the easy way and ordered an inexpensive one from Amazon.

And since I had long ago followed Hanley's lead and installed an oxygen sensor in the manifold close-off plate to run a Fuel:Air Ratio gauge, removing the oxygen sensor provided a perfect place to inject the smoke.

And it worked! I found THREE streams of smoke coming from somewhere on the underside of the MMI exhaust flange, just out of sight. By touch I dislodged large flakes and chunks of rust from the flange (its AMAZING how much rust a little bit of mild steel can make!), and found the SS bolts to be in perfect shape. But this is where my luck ended.

I have spent weeks trying to get those bolts out. The upper one is particularly difficult, as the first elbow blocks access with a socket wrench, and I can only get to it with a box end wrench. I soaked it in Kroil. Tapped on it. Soaked it some more. Tapped some more. Tapped on the wrench with a small hammer. Applied heat to the flange and manifold with an electric heat gun. Upped the ante to a micro butane torch. And when that failed, rearranged hoses and wiring out of the way as best I could and applied a plumbers MAAP torch! Still no joy. At least I didn't set the boat on fire.

I transferred my attention to the lower bolt, which could be accessed with a socket wrench. Applied lots of Kroil, and successively tried a 12" ratchet handle, an 18" breaker bar, and finally managed to get a Ryobi electric impact driver in there and cranked on it until the 6-point socket was getting hot from just the impacts! Never budged. I tried this repeatedly, alternating with Kroil until my shoulder gave out.

And that's where I am today. Access is really difficult. I either have to squeeze in over top of the engine, or reach down and in from one of the cockpit lockers. I managed to get my phone in there and snap some pictures, and was astounded to find that the MMI flange has completely cracked through (!), right next to the boss for backpressure testing. This expansion is probably pinning the bolts in place.

So I'm open to suggestions. The SS pipes are in perfect condition, so I really don't want to hacksaw them off. In the past, working on car exhausts, the answer has always been "More Heat!", but my only option for that is an Oxy/Actelyne torch!!

At this rate, I'm going to lose the rest of the season!
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Old 07-13-2022, 04:28 PM
Dave Neptune Dave Neptune is online now
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Edward, did you try both loosening and tightening with the impact? I have gotten quite a few jammed things apart going both ways. Got many big grinding machine parts apart like that.

Otherwise because the bolt heads look well sealed it will be difficult to get anything sucked into the threads. Perhaps drill a hole through the flange down to the bolt will give the lube some access to soak in. Then you can work the manifold on a bench.

Maybe hack sawing the heads off or getting the washer to split under the head with a chisel might get some lube to soak in.

Dave Neptune
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Old 07-13-2022, 06:54 PM
TimBSmith TimBSmith is offline
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Edward thanks for post, epic erosion and bolt removal challenge.

As a low risk learning exercise I recently broke down an old A4 that was terribly rusted inside and out. One technique I found surprisingly effective, in tight spaces, once a part was rendered unusable/consumable; was a patient careful Dremel with a metal cutting wheel to relieve pressure near the bolt head and to improve oil penetration. The metal cutting wheel and sharp cold steel punch worked to cut then open a release point on the Moyer flange, the thermostat housing, and the coupler, all areas that just would not give or where bolt heads had nearly rusted off.

I did not have to support the riser, I expect you do/will, especially the heavier stainless build. I used a fan on lazarette for cooling, goggles, respirator, tight gloves, and some splash/ masking to bounce metal chips toward pig pads in the bilge. I experimented with cutting oil to keep chips more under control. Kept a fire extinguisher beside me. Getting access meant removing marine exhaust hose from water lift muffler, and repositioning and zip tying wiring harness. I wore knee pads. I stacked foam padding in the bilge at the front of the engine beside transmission for elbow support. Impossibly fit most of my trunk sideways beside engine. I have literally spent hours adjusting padding in hard to reach places like this to establish a functional working position with leverage. (That you fit a breaker bar into your space is quite a feat). Last thought is using a small bottle jack once riser is supported to lift the broken flange and change the pressure on the bolts. Keep us posted. Best of luck.
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Old 07-13-2022, 10:22 PM
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Studs my friends. The fastening system (hex nuts) is then on the outside of the flange, not buried deep in the manifold. If they want to seize solid in the manifold, don't care anymore.

This follows the same reasoning as the water jacket side plate studs.
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Old 07-14-2022, 10:01 AM
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Are you doing this with the manifold on the engine?
I would be taking that off and working on this at home.
The smoke trick was a good idea, my low-rent version is dumping MMO in the carb and seeing if any smoke comes out from anywhere.
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Old 07-14-2022, 11:25 AM
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Quote:
Originally Posted by ndutton View Post
Studs my friends. The fastening system (hex nuts) is then on the outside of the flange, not buried deep in the manifold. If they want to seize solid in the manifold, don't care anymore.

This follows the same reasoning as the water jacket side plate studs.
Yes, I know. I put the bolts in knowing that studs would be much better (I have them on the side plate). It just made the assembly much easier. I also suppose that in the back of my mind was the thought that I would never be disassembling this again. Kicking myself now!
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Old 07-14-2022, 11:30 AM
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Have you figured out WHY the flange is so rusty? Normally there should be no water in it or on it.
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Old 07-14-2022, 11:35 AM
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Quote:
Originally Posted by Dave Neptune View Post
Edward, did you try both loosening and tightening with the impact? I have gotten quite a few jammed things apart going both ways. Got many big grinding machine parts apart like that.
No. Good tip. I'll try that on the lower bolt.

Quote:
Originally Posted by Dave Neptune View Post
Otherwise because the bolt heads look well sealed it will be difficult to get anything sucked into the threads. Perhaps drill a hole through the flange down to the bolt will give the lube some access to soak in.
Another good idea.

Quote:
Originally Posted by Dave Neptune View Post
Then you can work the manifold on a bench.
My geometry is such that the manifold can't come out until the riser is off, and the riser won't come off the short exhaust hose to the waterlift until the riser is loose from the manifold.
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Old 07-14-2022, 11:41 AM
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Quote:
Originally Posted by joe_db View Post
Have you figured out WHY the flange is so rusty? Normally there should be no water in it or on it.
I know. It seemes excessive, even for 11 years. Its possible that a defect in the weld for the backpressure testing boss was the starting point, but i would think that much corrosion would need moisture. Yet another mystery to solve.
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Old 07-14-2022, 03:30 PM
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Lightbulb

Edward, when ever I wrap these types of exhaust I leave an inch or two of the pipe exposed. Condensation in some conditions can drip and/or keep things damp unless running.

Dave Neptune
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Old 07-16-2022, 02:45 PM
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Moral Support

Edward, after years of reading the forum, learning a lot, and 'getting to know' many of you guys through your posts and humor, I can only say, to read your first post on this thread feels like a loved one has just told me that they have been diagnosed with a treatable, but debilitating disease.

I don't have any special tips or tricks to share, but do want to say as part of your Afourian 'family', we are with you while you get through this. If you need a therapeutic day sail on an a-4 powered boat in the Boston area, send me a note...

It may be painful, but you'll get through this!
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Old 07-17-2022, 11:28 PM
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Wagner,

Thanks for the kind words. They really do help.

Meanwhile I've got a family emergency that has been taking up all my time.
I'll post more status when things calm down a bit.
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Old 08-07-2022, 02:48 PM
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Because of the aforementioned family situation, I've only been able to get down to the boat once about once a week, so progress has been slow. Here's a somewhat scattered update:

Got a second person to help by applying heat with the MAAP torch on the upper bolt while I simultaneously applied torque with a wrench. No joy.

I tried Dave's suggestion of alternating the impact wrench's direction fwd and backward on the lower bolt while soaking it in Kroil. Did this until the battery was exhausted. Never budged.

Using a Dremel with a 1/8" diamond bit, I carefully drilled a small hole in the flange near the upper bolt. I could feel it when the bit broke through the flange into the region between the flange and the bolt. Put copious amounts of Kroil on the hole and retried the whole gamut of wrench, hammer-tapping, and heat. No progress.

Since the first hole was pretty close to the bolt head, and the flange is wide, I tried to drill a second hole, closer to the manifold. I reasoned that this would make it easier for the Kroil to get to the manifold threads. I was careful to brace the drill well so I didn't tilt it and snap the expensive diamond bit. The hole drilled straight and true, and as soon as it broke through, it seized up and snapped the bit off below the surface! At least I had a hole through that would let the Kroil in. More wrenching, tapping, and heat, and no progress.

At this point, I returned my attention to the lower bolt, Trying the breaker bar again, with no results. The little 1/4" drive battery impact driver I had been using only has 150 lbs of torque, so I got hold of a 1/2" drive one that has 300 lbs of torque. And it appeared to work with only a half dozen impacts and then spinning free!

Alas, I quickly discovered that the bolt had sheared off about 1/2" below the head. I suspect that my previous attempts with the impact and the breaker bar had already stressed it close to the breaking point, as it broke almost immediately.

So that tears it. I'm now going to have to eventually get the manifold off to remove the broken bolt on the bench. Meanwhile, I STILL have to get the flange and the riser off. The goalposts keep getting farther away!

I got a cutting wheel on the Dremel and started cutting a slot in the flange near the upper bolt. Tried to get a cold chisel in there and hammer on it, but there was too much plumbing in the way. Since I'm now going to have to remove the manifold, I started pulling all the cooling lines and fittings, and the overtemp sensor, off the manifold to give me room to place the chisel.

So, that's where I am right now. Current plan is to cut and chisel enough bits off of the flange to free things. Stay tuned.
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