Diesel won't get hot + white smoke Yanmar 3QM30

[nelly]

Thanks all. Replaced thermostats. Air was getting in by some of the old crush washers. Replaced those and no more air issues.

Ran at full throttle for a half hour or so and the engine got up to just over 160 on the digital reader, which means it was probably closer to 170 (realized it reads between 5-10 cooler than a infrared says - I have two guns both say the same).

Then stayed at that temp, when I throttled down it did cool a bit - probably to around 130-140, but it was a very cool day (40s).

Seems to be running fine now with no smoke. Impellers and all are fine. I'll replace the belt over the winter and do some additional work.

Fuel tank absolutely needs to be scrubbed. That'll be fun.

[Compass790]

Good that you got it sorted. Don't put off cleaning the tank or you'll be sorry. Ask me how I know

[nelly]

It's getting cleaned. Good access to the tank but not looking forward to it.

How did you cut an access port for your tank? I'd like to cut something larger if I can. I'm thinking about 1' or so? So I can really see in there and get around in the tank.

Also going to put biocide in it as soon as it gets here on order. Hope that'll break **** up and make it a little easier?

[pismlord]

Already mentioned but had the same white "smoke" with my My yanmar 3ym30
Turned out to to be steam caused by blocked hose outlet at the exhaust elbow
Once cleared the steam issue was immediately resolved

[hellosailor]

"Air was getting in by some of the old crush washers."
I hate crush washers. If you remember the old Abbot and Costello routine, "Niagara Falls!" that's how I respond to crush washers.
But as long as you have them, buy a BOX FULL of them. They are meant to be used once and thrown out, and that means anytime you bleed the engine and crush washers are involved, they all should be replaced, each time. They're cheaper in bulk.(G)

On Symphony's question about changing thermostats. A thermostat is baffling to look at, there's no obvious way to how it works. What there usually is, is a small cylinder filled with a thermal wax. Wax, really. It expands and contracts a great deal as it heats up, and that makes the cylinder expand and contract, which is what pushes the thermostat "gate" open. Then there's a big external spring to help it close again.

Now that wax cylinder can last 25 years with no problem. Wax and brass are both pretty stable. But if the assembly wasn't perfectly sealed and some wax eventually leaks out, you're dead. Personally I like to ignore the faithful servants and let them be in peace. Coolant tank pressure caps are more likely to fail, since any time you open the cap, crud can form around the seal and lead to some eventual failure.

And I learned the hard way, even a brand new brand name thermostat can be DOA. I won't use one unless I've put it in a pot of water and watched it cycle as the water is boiled and cooled. Cheap insurance against all the misery of a new DOA thermostat and wondering "Overheating? Still?!"

[Pete7]

Originally Posted by odonnellryan

How did you cut an access port for your tank? I'd like to cut something larger if I can. I'm thinking about 1' or so? So I can really see in there and get around in the tank.

On a previous boat with a stainless steel tank I bought a box of 6mm drills and just started drilling. Used most of the box, probably a dozen but it did the job. Cleaned off the rough edges with an angle grinder, then cleaned the swarf out of the tank.

Now you can buy electric saws that will cut steel if you don't fancy my rather redneck approach. Can I say that on a 'Merican forum

Pete

[Compass790]

Originally Posted by odonnellryan

It's getting cleaned. Good access to the tank but not looking forward to it.

How did you cut an access port for your tank? I'd like to cut something larger if I can. I'm thinking about 1' or so? So I can really see in there and get around in the tank.

Also going to put biocide in it as soon as it gets here on order. Hope that'll break **** up and make it a little easier?

Well our tank is removable so i took it out & washed it out with petrol ( gasoline) & turned it upside down. It looked like bitumen the stuff that came out. You can cut a hole with a jigsaw with metal cutting blades. You'll need plenty of blades & use cutting fluid.

[lituya1617]

Good discussion but the information available makes it hard to point to a cause of the smoke/overheat/underheat/low power problem. I get the impression that the diesel has been neglected and the current owner is not a Yanmar mechanic. If you have a shop manual, do what it says. Yanmar shop manuals are wonderfully detailed and helpful. I would never touch a diesel without the manual in hand because there are a lot of things you can futz up. Having said that, 1) high loads make Yanmars give off black smoke which turns the cooling water discharged black or dark gray, this is normal. 2) Running too cool means you have to replace the thermostat at least. You may need a new guage too. 3) The fuel system you played around with only needs to be clean, not massaged. 4) A bit of white smoke that quickly dissipates is simply steam but it means you are not passing enough water into the exhaust to cool it. This means you have to check the amount of water being squirted into the mixing elbow. It is usually possible to catch the outflow in a bucket from a dingy at the stern. The pump is rated to pump a certain amount per minute - see specs in the manual. If it is not pumping enough, you have to fix the cause. There may be an obstruction, dirty heat exchanger core, fouled intake, or burned-up rubber impeller in the raw water intake pump - the most common causes. When you reassemble the raw water pump, make sure you put some light grease on the impeller so you do not damage it before it begins to be lubricated with water on start up. 5) Unburned fuel would be blue smoke and indicates an injector or compression problem; however, the mixing of water with the exhaust makes this difficult to detect. If the exhaust smells of diesel oil or has droplets of oil that make a sheen on the water, check your injectors. 6) Inability to reach design RPM indicates improper prop size/pitch, a fouled prop like with a line, insufficient fuel reaching the injectors, a faulty injector (s), poor compression, a clogged intake manifold (rat's nest?), and a number of other causes. If your diesel puts off black smoke or black water when you open the throttle to maximum, it is getting enough fuel at least, maybe too much. In summary, replace thermostat, replace raw water pump impeller and dig out any pieces that it may have shed into the water system, make sure your diesel fuel is pristine, and do not do anything the manual doesn't suggest.

[nelly]

Thanks guys. I think smoke is gone. I thought it was steam but I think it was just white smoke from having air in the lines. Seems fine now and is running without any smoke or anything.

But, there is crud in the clear bottom of the fuel filter. Fuel needs a good cleaning absolutely

I'll have to triple check but I think I have an aluminum tank. That would be nicer to cut anyway. I'll find out soon enough

No way to remove this tank, I know that for sure. It's tabbed in with fiberglass, and even if that wasn't the case I'm not so sure I could git it out of there anyway without removing a bulkhead!

All really good comments. I didn't do any major work on the engine. Just fuel lines and coolant lines replaced, no engine work really. I did break the bleeder bolt on top of the injector b/c of over tightening (though I really don't think I tightened that much - maybe it was already damaged) but it didn't come apart or anything just cracked, so that was lucky.

Thanks again. Really good stuff!

[MarkSF]

If you're just pointing the IR thermometer at the aluminum housing, the results can be all over the place due to varying emissivity of the metal.


Better to stick a piece of black tape over the metal, and read the temp of that. Of course, it will still be a bit cooler than the coolant.

[nelly]

Originally Posted by MarkSF

If you're just pointing the IR thermometer at the aluminum housing, the results can be all over the place due to varying emissivity of the metal.


Better to stick a piece of black tape over the metal, and read the temp of that. Of course, it will still be a bit cooler than the coolant.

That's a great idea. It's funny because IR reads higher than the coolant thermostat (which is new). I assume it just isn't calibrated or something. Not a lot. 5-10 degrees higher.

[Compass790]

Originally Posted by odonnellryan

Thanks guys. I think smoke is gone. I thought it was steam but I think it was just white smoke from having air in the lines. Seems fine now and is running without any smoke or anything.

But, there is crud in the clear bottom of the fuel filter. Fuel needs a good cleaning absolutely

I'll have to triple check but I think I have an aluminum tank. That would be nicer to cut anyway. I'll find out soon enough

No way to remove this tank, I know that for sure. It's tabbed in with fiberglass, and even if that wasn't the case I'm not so sure I could git it out of there anyway without removing a bulkhead!

All really good comments. I didn't do any major work on the engine. Just fuel lines and coolant lines replaced, no engine work really. I did break the bleeder bolt on top of the injector b/c of over tightening (though I really don't think I tightened that much - maybe it was already damaged) but it didn't come apart or anything just cracked, so that was lucky.

Thanks again. Really good stuff!

FYI thats not a bleeder bolt on top of yr injector, its for the fuel return line. You bleed injectors by cracking the nut at the injector that secures the high pressure feed pipe from the injection pump.