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Discussion Starter · #201 ·
OK. Here we go.

First image.
84 Degrees outside.

Up through 28 minutes, business as usual. Then, I popped open the hood. At 34 minutes, I blocked off the area between the instrument panel, and the radiator until 43 minutes. At that point, I ran max engine speed no load with the hood open to cool. Shut engine off at 48 minutes.

The reason to pop the hood was to see what the change in airflow would be, and how that would affect the temp. Additionally, I wanted to see how much the area between the top of the radiator and the instrument panel sucked in cool air. The difference was about half and half between the fresh air suction above the radiator, and hot air venting. Measurable amount of air flow difference through the radiator.

Second image.
84 Degrees outside.

I removed my hood, and installed the hood off of a 318. Yellow and Grey are Oil temp. Blue and Orange are Radiator Inlet temp. The ambient temperature was the same. By this comparison, it is clear to me that the hood noise insulation that I installed does not affect the temperature at all.

I did get bubbles in my sight glass for the overflow. This means either I have an air leak into the cooling system, the cooling system created air, or head gasket.
 

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Discussion Starter · #204 ·
I was leaning towards head gasket because it's the only thing in the service manual left (aside from fuel timing). However, if bubbles were in the system, it would have displaced the coolant. This morning when I checked it, the recovery bottle was completely empty. And when I pulled the radiator cap, the coolant level was right where I left it, filled right to the brim with no expansion volume.

I should think cavitation wouldn't be an issue using the Deere yellow coolant, which says it has all the anti-cavitation additives in it already. I just checked the date that I had changed from unknown age green coolant to yellow coolant. I've had yellow for 4 years, so I've been using it the whole time I've had the MCS.
 

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Unless the bubbles get trapped somewhere, they won’t necessarily displace the coolant. As long as there is decent flow, it would continually burp itself.
 

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It seems to me that air bubbles are compressible, steam bubbles are not. The coolant would overflow if it's overheating (creating steam bubbles) but not necessarily if the bubbles were caused by cavitation. Most of what I know about cavitation will fit on the head of a pin if children's letter blocks were used to spell it out. So this is what I think I know - cavitation creates micro-sized bubbles that are erosive to the metals they hit. Like little sandblasting bubbles. The bubbles don't really increase the volume of the liquid they are being made from. The bubbles create foam more than visible bubbles (they make the liquid cloudy like an emulsion). The foam returns to a liquid state rather quickly. However, foamy liquid can't absorb (transfer) heat as well.

Some, all, or none of that may be true.
 

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Discussion Starter · #207 ·
Nailed it Randy. You are absolutely correct.

But why would it be cavitating so badly? Brand new pump, new Deere Yellow Diesel coolant. It did overflow coolant, but it took it all back in when it cooled overnight. I feel like I should just pull the head and have a look. That way I can at least eliminate the head gasket as a problem. At the same time, check on the health of the bores, piston tops, and the head for flatness. I think a head gasket kit is like 60 bucks. It's just time...

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Discussion Starter · #208 ·
Kinda grasping at straws here...but has anyone with a 332 painted their belly screen? It just occurred to me that I cleaned up and painted mine, probably spring of last year. I made sure the mesh holes were clear, but maybe the paint was enough to make the entire mesh a significant % decrease in free flowing area. Death by 1000 needles syndrome? Each hole only slightly smaller diameter opening now but there are a TON of holes.

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My 1755 Oliver diesel is a Waukashaw engine block. It's a sleeved block. A known issue is cavitation around the sleeves eats away at the sleeve supports near the bottom of the sleeves where the water jacket seals around the sleeve base. That seems an odd place for cavitation but I saw the damage. I asked the mechanic if it was caused by the heat of the cylinders but he said no, diesels should not have cylinders that get hot enough to boil antifreeze. It's the movement of the water through the smallest passages at high speed. He said it's hard to slow the water speed down without creating problems in the head and valve areas. That's the reason for water wetters (anti-cav chemicals). They reduce the surface tension of water leading to a lesser amount of microscopic bubbles being entrained or emusified into the coolant.

With that said, a modern engine has had many of these coolant issues designed out of them. So my thinking is that maybe the Deere coolant doesn't go far enough with the anti-cav additives? Maybe a extra dose will help? Or not, I don't know. Might be something to call Prestone, Zerox, or another big name coolant company and ask about. Lucas oil might even be easier. Or a high falutin race shop.

Again, just hearsay, I can't vouch for the validity of any of this, it's just what I know.
 

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I looked up the cause of cavitation. According to several articles, its caused by vibration. A sleeved cylinder vibrates with piston movements, causing it. But it also happens in non sleeved engines.
It used to be much more common 20 + years ago when I started in a diesel shop. These days with new engines, not so much. But, here is a 35 year old tractor, so it a definite maybe.
Now keep in mind, the truck engines I saw with the issue were old and had many hundreds of thousands miles on them. They also ran all day, every day. In other words, it takes a while before anything bad happens.
I would think the cavitation would have to be extreme to cause this issue.

I know the OP stated the injectors were replaced/cleaned. I'd have them tested. They absolutely have to meet the minimum pop open pressure, usually 3500 psi. With a nice wide, fine spray mist when they do.
Then I'd look into having the injector pump checked for delivery. That probably requires removal and sent to a specialized shop.

After that, id consider removing cyl head. But, do a compression test first. I'm not sure on the yanmar diesel, but they usually have a copper washer that the injector seats on. It seals the cyl. A lot of times theres a copper bowl that's pressed in that's seals the coolant jacket. Either of these could be leaking slightly, causing this issue.
The cyl head could have a pre combustion chamber to. The glow plug locates in it. An isuzu NPR 4 cyl diesel engine were notorious for getting a crack in that pocket.
If you do pull the head, I'd get it magnafluxed and checked for a crack, by a good machine shop, that knows what there doing.

Ok, brain overload, it's to early for this much thinking, lol. I'm going to go change oil/filter and relax, lol.
 
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Detroit Diesel Series 60s had a problem with cavitation. During combustion the liner will expand, and when it contracts back after the bang it causes a vacuum pocket in the coolant allowing it to rapidly boil and that causes tiny explosions that eat away at the liner. They formulated a coolant to prevent that (Power Cool), it actually put a thin protective coating over the internals. Great coolant! Also had a cleaning aspect to it. The dirt particles would get coated and then they would float around since they would stick and could be flushed out. I use it in all used vehicles I purchase.
 
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This is a great thread and I hope that it helps us to figure out what will help this Yanmars live, be it EGT's caused by any number of things (timing, fuel restrictions, increased fuel duration), poor cooling system design, or some sort of an overheat condition caused by intake air temp (I have seen this in LLY Duramax's) My experience in light duty diesels and rebuilding / repairing 2 430's and a 330. All three with HG failures and 2 with low compression that I suspect came from overheat related factors. I am working on my current 430 as we speak and will be glad to collect some data as well from a fresh engine if anyone needs anything (EGT readings, coolant temps, intake air temps, etc) Just throwing my hat in the ring if I can be of any help to find the root cause.
 

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Discussion Starter · #213 ·
As a side note. Per our discussion LONG ago now about the thermostat being a suspect. Per TM1591, the thermostat should begin opening at 71C (160F), and have a minimum lift of 8mm at 85C (185F) full open position. This I determined to be wrong in that I purchased 4 brand new thermostats, all of which stroked about 6mm, as did my original thermostat.

I sent Yanmar an inquiry last night about this. I received a phone call this morning from a very helpful service support manager. He informed me about the engine (3TN66UJ) being Deere specific, which most of us here already know. I explained that Deere was not helpful at all, and just referred me to the dealer. He gave a chuckle, and told me that he gets this kind of stuff all the time, especially with the older machinery. He went on to explain that the original manual TM1591 was translated from Japanese. Which makes perfect sense since it is a Japanese company/engine. Lots of stuff can be lost in translation.

Now, since a 3TN66UJ is basically the same as a 3TN66E, which happens to be a "Yanmar spec" engine...he looked up the specification for that engine for me, and below is what he said.

71C (160F) first opening of the thermostat is correct. 85C (185F) maximum opening of the thermostat is also correct.

The opening specification at 85C is 4.5mm minimum, 8mm maximum lift.

So, we now have definitive proof that the spec in TM1591 is incorrect, and we have the actual real numbers. I suspected this before, but it's nice to have a min and max lift spec to refer to instead of an educated guess.
 
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That would result in a substantial increase in flow!

Didn't you try to to run it without a t-stat before?

That engine is right on the design limits of accuracy... too much flow (too quick) and not enough time to transfer enough heat out. Too little flow by just a little and too much time absorbing heat with too small a radiator getting rid of it.

Maybe the solution here (if this may in fact be the entire issue) is to mount an auxiliary fan cooled solution outside the engine compartment? Harley has some nice small oil coolers that are fan cooled. Like all Harley parts though they are over priced and under engineered. I'd even think a heater core from an old pickup truck that was fancied up some and simply mounted in front or behind the tractor out of the way would help with the few degrees that's necessary to get the temps down. Even a power steering two pass cooler might work well enough...just thinking out loud...
 

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Discussion Starter · #215 ·
I have not tried without the thermostat yet. But I don't see any reason to now that I know mine is good.

More flow through the radiator won't hurt*. The change in temperature across the radiator will decrease as flow rate increases, but the inlet temperature will also decrease, which is what you're really looking for. There's is a balance of temp drop across the rad and mass flow that is optimal (in order to minimize pump cavitation and pressure, and maximize heat rejection), but more flow won't hurt (cavitation asside). That's an all too common misconception.

*Now if there is an alternative place for coolant to flow (like lots through radiator, and not a lot through the engine), that could be bad. The old Yanmar doesn't have any other place to flow though, so in this case it doesn't matter.

Heat rejection = mass flow * specific heat * change in temp

With a super high mass flow, the change in temp will be very little, but the peak temperature will be lower. At which point you'd need to increase the face area of the radiator, or increase the radiator airflow, or both, if you wanted more heat rejection (or lower rad inlet temp). If you decrease the mass flow the change in temp will go up, and the peak temp will go up (which of course is bad).

That was probably confusing, but it is correct. Easier to explain graphically and with math...

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Graph maybe...add math to explanation and I'm outta here! ;) :LOL: Numbers and my brain are like oil and water....if they do mix - it all comes back out a milky mess...
 

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So I just read all 11 pages and i felt like i was reliving my whole experience with my 332 2 years ago. I did everything that you mentioned. I dont remember why I did it but i had my belly screen off of mine for some reason and had forgotten to put it back on before i mowed. When i did that my light never came on. I hadn't changed anything else, I have not put it back on as im to afraid to see that light come back on.

Just a thought. maybe ill get brave and put it back on and see if that really was the issue but I had my radiator cleaned re cored and painted, replaced injectors, therm, everything. Nothing was working until i had that screen off.
 
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