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Old 03-05-2013, 15:32   #31
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Re: Yanmar Maintenance issue: Mixing Elbow

I am NOT recommending that you do this, BUT, I was curious about the comments of using Muriatic Acid to clean one of these elbows out.

So,,, After 6 hours in Muriatic (about 30% Hydrochloric Acid) Here is what it looks like.

It cleaned out the water jacket, but did not do very well in the exhaust chamber.

My thought is that for this much trouble, buy a new one and go Stainless as suggested by David M.

Note: Muriatic acid is very nasty stuff and protective equipment must be used.



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Old 03-05-2013, 16:24   #32
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Re: Yanmar Maintenance issue: Mixing Elbow

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Originally Posted by Capn Dan View Post
I am NOT recommending that you do this, BUT, I was curious about the comments of using Muriatic Acid to clean one of these elbows out.

So,,, After 6 hours in Muriatic (about 30% Hydrochloric Acid) Here is what it looks like.

It cleaned out the water jacket, but did not do very well in the exhaust chamber.

My thought is that for this much trouble, buy a new one and go Stainless as suggested by David M.

Note: Muriatic acid is very nasty stuff and protective equipment must be used.



You're right about that. Muriatic acid fumes can really damage your lungs.
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Old 03-05-2013, 18:36   #33
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Re: Yanmar Maintenance issue: Mixing Elbow

If anyone interested in stainless steel exhaust elbow, there is web site were a gentlemen make them in u.k. Prices are not that bad. He make elbow for yannar 1gm, 2gm, and 3gm motor. Here is site below for anyone who interested.

www.exhaustelbow.com
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Old 04-05-2013, 03:01   #34
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Re: Yanmar Maintenance issue: Mixing Elbow

Capn Dan, thanks for your impressively informative and thorough contribution to the sum total of info on this topic. Even just having a sectional view through the elbow will be significantly helpful to some people reading this in future.

One issue with muriatic acid on cast iron, for those who want to try this on a non-reject part, is that it can set off a vigorous rust habit. I'm not sure what the best approach would be to nip this in the bud: presumably immediate and thorough rinsing in a solution of baking soda (sodium bicarbonate) would not be a bad idea.

Anyone have an idea on this?
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Old 04-05-2013, 04:41   #35
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Re: Yanmar Maintenance issue: Mixing Elbow

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A couple of us guys was talking about exhaust elbow today. What caught attention was, one gentlemen was saying why not try using fiberglass exhaust elbow, there would be no rust, and the heat absortion would be less also. Is this correct thinking of using exhaust elbow of this type and do they made product of this type
Hmmm... given that the portion of the exhaust elbow nearest the engine could reach temperatures of 1200 deg F, I don't know of any resin which would handle that.

Fiberglass exhaust piping and components, even downstream of the water injection which cools the gases considerably, needs to be SAE J2006 or equiv, made using fire-retardant resin to Milspec Mil-R-21607.

However even these could be in trouble if the water injection clogs. Mercifully the more usually chain of events resulting in no cooling water to the elbow will seize the engine before too much damage is done.

(PS: as an afterthought to my last post: perhaps the corrosion could be arrested with a phosphoric acid-based "rust convertor") - at all costs, avoid using anything which will bake or burn on, such as an oil-based product....)
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Old 04-05-2013, 04:48   #36
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Re: Yanmar Maintenance issue: Mixing Elbow

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If anyone interested in stainless steel exhaust elbow, there is web site were a gentlemen make them in u.k. Prices are not that bad. He make elbow for yannar 1gm, 2gm, and 3gm motor. Here is site below for anyone who interested.

www.exhaustelbow.com
Thanks a lot for that. Order placed. I'll report back on quality.

BTW: He seems to be US, not UK based.

Makes no diff; shipping is included to any destination, which is a nice touch given the target market.
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Old 04-05-2013, 10:22   #37
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Great thread. Take Away: Water injection elbows are replacement items. Inspect them periodically and carry a spare.
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Old 04-05-2013, 10:56   #38
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Re: Yanmar Maintenance issue: Mixing Elbow

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Hmmm... given that the portion of the exhaust elbow nearest the engine could reach temperatures of 1200 deg F, I don't know of any resin which would handle that.

Fiberglass exhaust piping and components, even downstream of the water injection which cools the gases considerably, needs to be SAE J2006 or equiv, made using fire-retardant resin to Milspec Mil-R-21607.

However even these could be in trouble if the water injection clogs. Mercifully the more usually chain of events resulting in no cooling water to the elbow will seize the engine before too much damage is done.

(PS: as an afterthought to my last post: perhaps the corrosion could be arrested with a phosphoric acid-based "rust convertor") - at all costs, avoid using anything which will bake or burn on, such as an oil-based product....)
This makes me wonder if there is a way to indicate the condition of the mixing elbow based upon its temperature???
When clogged, do they start to get hotter?
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Old 04-05-2013, 11:21   #39
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Re: Yanmar Maintenance issue: Mixing Elbow

Mixing elbows are not brain surgury. I made one for my MD2B VOlvo out of galvanized pipe. It was simply a T and a 45 degree elbow assembled with threaded nipples. The raw water pumped into the side of the T and out it went. A lot less chance to clog up than the restricted passage on your Yanmar. material that doesnt scale up would be best, stainless, or maybe even aluminum. On another boat I had one welded up out of Inconel 625.... but that's another story....
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Old 04-05-2013, 22:39   #40
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Re: Yanmar Maintenance issue: Mixing Elbow

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Hmmm... given that the portion of the exhaust elbow nearest the engine could reach temperatures of 1200 deg F, I don't know of any resin which would handle that.
They could be better than you think. I repaired a broken flange on a cast iron car exhaust manifold. It was right at the point where it was bolted to the head, and I thought it would only be only temporary. It was still holding together and stopping the exhaust leak after 3 or 4 years when I sold the car.

That was epoxy putty in a stick bought from any auto accessories. You just cut off a length and knead it in your fingers to mix and start the set process. I think it was called Instant Steel or something similar.
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Old 04-05-2013, 23:05   #41
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Re: Yanmar Maintenance issue: Mixing Elbow

That's an interesting observation, Wanderlust .... but I think it's not a particularly tough call for a material to retain sufficient strength at high temperatures to plug a narrow passageway.

It seems to me it could easily do that even if its strength was drastically reduced, maybe to only 10% of the rating at normal temps.

You can stuff something with very little strength, an extreme example being a rag, into a narrow gap, and it stays put if the material around it stays strong. If it's a piece of racing-driver flamesuit, it'll stand the heat, too....

As another example: take a champagne cork. It can take lots of pressure, even in a smooth, cylindrical hole, but I don't think there would be much future in making champagne bottles out of cork.

I guess I'm trying to suggest, probably not making much sense... that it seems to me entirely another thing for the same material to be laminated into an entire structure, which needs to retain sufficient mechanical strength to resist internal pressure and the localised forces at the attachment points.

The highest temperature rating for an industrial epoxy resin I'm familiar with is RESOLTECH HTG 240, which is good to 240 deg C, which equates to 464 deg F, as a continuous rating.

In the home handyman range, JB Weld do a high temperature putty specifically for exhaust leaks: it's rated to 400F continuous, or 550 intermittent.

I don't think either of these would stand a chance if you were to make an entire exhaust elbow for a diesel engine out of them, regardless of the thermal rating of the reinforcing fibre.
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Old 04-05-2013, 23:09   #42
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Re: Yanmar Maintenance issue: Mixing Elbow

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This makes me wonder if there is a way to indicate the condition of the mixing elbow based upon its temperature???
When clogged, do they start to get hotter?
The standard way is to have a tapped hole at the entry end of the elbow for connection of a pressure gauge. This should only be connected briefly for diagnostic purposes, when the engine is not hot, unless you have shares in a gauge company !

Leave a stainless steel pipe plug in there the rest of the time...

The back pressure gives a good idea of the condition of the passageway: obviously you need to measure it when it's unobstructed for that engine, to have a baseline.
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Old 05-05-2013, 10:01   #43
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Re: Yanmar Maintenance issue: Mixing Elbow

I repaired a heat exchanger fitting (Brazed fitting on the copper alloy) using an epoxy type stuff once. It lasted half an hour.... be careful what you try to use!

This makes me wonder if there is a way to indicate the condition of the mixing elbow based upon its temperature???
When clogged, do they start to get hotter?

It's pretty common on commercial diesels to monitor exhaust temperature. I would think it would show it well... when restricted , by water flow or exhaust restriction the temp would rise.
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Old 05-05-2013, 13:45   #44
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Re: Yanmar Maintenance issue: Mixing Elbow

A note on acids. Rather then use muriatic acid for cleaning, which promotes rusting on cast iron and steels, use a phosphoric acid which will coat the metal with a phosphate coating, inhibiting rust formation. Phosphoric acid is available in many hardware stores around the painting department.
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Old 06-05-2013, 01:14   #45
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I repaired a heat exchanger fitting (Brazed fitting on the copper alloy) using an epoxy type stuff once. It lasted half an hour.... be careful what you try to use!

This makes me wonder if there is a way to indicate the condition of the mixing elbow based upon its temperature???
When clogged, do they start to get hotter?
It's pretty common on commercial diesels to monitor exhaust temperature. I would think it would show it well... when restricted , by water flow or exhaust restriction the temp would rise.
I'd replace it properly, measure water consumption on the intake side and make a note of how much it uses in good order.
After replacing mine, I had no question about the difference.
I used high temp(pure nickle) anti seize on all joints so next owner will have an easy time replacing it.
Not sure I'd try to push the life of the part, a failure of the casting would suck(looked to me to be a good way to get water into engine)
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