Can this Yanmar Heat Exchanger & Elbow be saved?

[TacomaSailor]

You guys were so helpful with the weak bolts I thought I'd try for more advice. The last couple responses to my "Weak Threads" thread suggested that the mixing elbow was defective, damaged, or a poor design.

I've attached two photos

The material on the heat exchanger front around the cap that holds the coolant bundle in place is badly corroded/eroded for about 40% - 50% of the circumference. The O-ring that seals the cap onto the HE face was protruding for about 1/2" of the circumference.

A local welder, with an excellent reputation in the local boating community, says he can rebuild that material and it will be as good as new (after I remove the exchanger bundle).

What would have caused that erosion of the material? There were no leaks at all, I kept a close eye on the cap because it is right above the 135-amp alternator and a leak or drip would be a disaster.

Can the material be re-deposited by a good welder?

The Yanmar Type U Silicon Bronze cast mixing elbow has about 1/4 of the upper surface of the inner tube missing. That tube carries the exhaust gas stream to the rear of the elbow where it should join with the raw water flow.

The missing material is downstream from where the exhaust gas stream makes a 90 degree bend to head down to the water lift muffler.

Does that hole cause any problems?

[DeepFrz]

I don't know enough about welding aluminum to comment on the heat exchanger but I would definitely replace the mixing elbow if it were on my boat. Perhaps after removing the heat exchange bundle others may be able to make more informed comments.

[delmarrey]

Two notes!
1) You can not weld cast aluminum, especially after its been impregnated with salt water.
2) I believe the mixer elbow is bronze, at least mine is. it would need a patch over the hole to be welded. Otherwise it would be full of porosity and start leaking again. It would be cheaper to just buy new in the long run. I found a new spare for mine at a consignment chandlery.

My only recommendation for a temporary fix to the end cap would be 3M 5200

[Old Snipe]

I would toss it and get a new one. But then.... it is easy for me to say when I am not the one forking out the money for a new one.

1. The tube bundle might be leaking by, or getting ready to soon. Why fix the gasket flange without punching and resealing the tubes? At least set up a pressure test on the bundle.

2. I am not knocking the welder, and it could be welded and machined, but there are other issues going on in the pictures from what I see.

3. It looks like you have a little thin wall going on in some areas.

[marlinmike]

My vote is for replacement as well, I know its expensive but you really have changed alot out up to this point, little more and you have everything 100%.

[Terra Nova]

Originally Posted by TacomaSailor

...A local welder, with an excellent reputation in the local boating community, says he can rebuild that material and it will be as good as new...

BULL!

[TacomaSailor]

Here are some details of yesterday's research:

Took the heat exchanger/manifold (HE) and elbow to the Yanmar dealer. He said many have tried to weld up those corroded housings around the cap and few have been happy for long. He looked at the mixing elbow and said it was the cleanest 20-year 2900 hour elbow he had ever seen. BUT, that hole in the exhaust gas tube is a real problem. It allows sea water to spatter back in the exhaust manifold. If the engine stops with an exhaust valve open it is possible for salty gas or even salt spray to get pulled back into a cylinder as it cools and makes a lower pressure IF the seawater comes back to the exchanger from the hole - I do not see how that could happen but it would not be good if it did.

New 4JH2E exhaust manifold and heat exchanger body $1,250 which DOES NOT include any fittings - sort of an engine short block (end caps, O-rings, nuts, bolts, radiator cap fitting, petcock for draining housing, EXCHANGER BUNDLE for the coolant are not included)

That means I have to get the bundle out of the current exchanger to either repair the exchanger housing via welding or to install the old bundle in a new housing. He said bangthe old bundle hard with a rubber mallet.

A new heat exchanger bundle is $850

OR - $2,100 for a complete cooling system including bundle, housing, all fittings and mounting hardware

He also thought it pretty important to replace the mixing elbow to keep the sea water from getting back to the new or repaired heat exchanger. The Type U elbow I have is a Yanmar part and is used to 1) get the exhaust and water flow 12" higher than a standard elbow 2) decrease the downward angle of the exhaust hose to allow it to connect to a waterlift muffler close to it's level.

New mixing elbow $850

WHY did this happen?
1) The mixing elbow damage is unavoidable because the hot exhaust gases have to make a 75 degree turn 6" after they leave the manifold. The inner tube of the elbow (contains and re-directs the gas) is very thin material and erodes over time. The Yanmar guy say few boaters experience this problem because the elbow clogs up with other stuff before the erosion occurs. It seems to me that a LOT of hot rods and diesel trucks have 90 degree bends just inches from the exhaust valve and those tubes do no suffer similar erosion. Or, do they after 120,000 miles or 2900 hours of usage?

2) The corrosion on the front of the HE around the O-ring is due to dissimilar material (aluminum exchanger, bronze end cap, steel bolts) and is pretty hard to prevent. He says that removal of the cap, bolts, and bundle every few years and a thorough cleaning with fresh water will slow the problem but it is still dissimilar metal.

Only four to five days to get a whole new system or $13,000 for an entire new engine! (but no elbow)

I took the exchanger and mixing elbow to the recommended welder who was friendly and talkative - he told me:

- Yanmar casting quality control is very poor
- Some castings are near perfect and very easy to work with and weld up nicely
- Some castings are so full of impurities that nothing will weld to it
- Some castings are poor and look like the weld will work but after a while it becomes apparent the weld will be low quality

I need to get the bundle out of the housing and then have it gently bead blasted. He estimated $50 to $100 for the beading. Then he will know within 30 seconds if the material in the casting is worth working on. His setup charge to do the first 30-second weld is about $50.

If the weld seems OK he figured about $300 - $400 for the welding and machining to give a flat face and an O-ring groove.

He has done quite a few and says that if he feels good about the welding after a couple minutes they always work out OK.

At that point I would have $500 invested in a 20-year old heat exchanger that might fail in some other way. Or, buy a new one for about $1,125.

Seems like a new one is a good idea.

[DeepFrz]

I think a new one is an excellent idea. A lot of money though. It is quite old and a new one will probably last quite a while, especially if you do maintenance on it as the dealer suggested.

[boden36]

When you are trying to remove the core, it may help to boil the assembly for a while or otherwise warm it - dissimilar expansion rates could make the job easier.

Regards,
Richard.

[gjordan]

Boiling is a good idea, and I would also consider soaking the whole thing in white vinegar overnight. It tends to clean corroded parts. I think I wont complain about Volvo parts anymore. Best of Luck. _____Grant.

[cheoah]

New. It's like tires, if it's questionable, just do it. It does look thin, in my mind, after doing an elbow not too long ago. My 1988 boat is on it's third.

If you only sail locally, without strong currents, heavy traffic, etc a break down is no big deal. If you're on the move, and need to keep moving, put a new elbow on there and keep that water flowing full force. Boil that one and put in emergency parts.

Dunno what to say about heat exchanger, I missed age or hours and can't see from this screen, but could be hot seawater. How's your zinc in there?


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[Captain Bill]

I just discovered a similar problem on my 3jh3ce that is only 12 years old, but I do have about 3000 hours on it. Oddly enough the other engine looks perfect after the same amount of time. My heat exchanger core has a small amount of erosion, but not nearly as bad as the OP's. Mine only extends about 10 degrees (1 inch) at the very bottom of the exchanger and there is still come lip left. The biggest problem I have is in the exhaust manifold/heat exchanger housing. I never saw any coolant leaking before I removed the cover but I did a leak test and found coolant in the raw water side. I knew I had a slow leak but couldn't see where I was loosing coolant. It was very slow. I would have to add coolant to the overflow tank every couple of months. I am going to try to repair the manifold with Epoxy. There is very little pressure at this position, Temperatures should never exceed about 170F. I have used Marine Tex in the past to make repairs in aluminum where conditions were much worse that what should be experienced here. I'm sure I'm going to get a lot of feedback about just sucking it up and spending the $2000 to replace it, but for the moment that is not the question I would like addressed. My question is should I be using Marine Tex or JB weld. Marine Tex seems to be rated as stronger, but has 250F temperature limit. Jb weld on the other hand has a 500F temperature limit. A mechanic friend many years ago showed me how to make tight joints using silicone grease on the opposing part and on an o-ring to make an o-ring sealing surface. I have never actually done it myself but it didn't look that difficult.

[Amnesia II]

If your riser is similar to this on your 4 cylinder Yanmar and leaks develop at the water injection area, don't bother with a weld repair....it's a waste of money, just fit a new one @ $375. And be done! That's my experience anyway!


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[Cheechako]

Originally Posted by TacomaSailor

You guys were so helpful with the weak bolts I thought I'd try for more advice. The last couple responses to my "Weak Threads" thread suggested that the mixing elbow was defective, damaged, or a poor design.

I've attached two photos

The material on the heat exchanger front around the cap that holds the coolant bundle in place is badly corroded/eroded for about 40% - 50% of the circumference. The O-ring that seals the cap onto the HE face was protruding for about 1/2" of the circumference.

A local welder, with an excellent reputation in the local boating community, says he can rebuild that material and it will be as good as new (after I remove the exchanger bundle).

What would have caused that erosion of the material? There were no leaks at all, I kept a close eye on the cap because it is right above the 135-amp alternator and a leak or drip would be a disaster.

Can the material be re-deposited by a good welder?

The Yanmar Type U Silicon Bronze cast mixing elbow has about 1/4 of the upper surface of the inner tube missing. That tube carries the exhaust gas stream to the rear of the elbow where it should join with the raw water flow.

The missing material is downstream from where the exhaust gas stream makes a 90 degree bend to head down to the water lift muffler.

Does that hole cause any problems?

Cast aluminum can be welded, but it's tricky and can be problematic. It all depends on if your welder really knows what he's doing I suppose. That looks pretty shot... but the new parts sound real expensive... One Old Yanmar I had had the whole heat exchanger separate from the engine. Connected with hoses... After market Heat exhangers are made (and not aluminum!) any way to convert that engine...?

[feebs]

So bringing this to top again.....

Having spoken to several Yanmar owners, most are or have suffered breakdown of HE lip alloy as above. Would installing an anode in one of the raw water end caps reduce or even eliminate this alloy from breaking down.

Much much cheaper replacing anode than replacing HE in total.