Over Heating of Yanmar 6BY2 260

[D & C M]

I launched my 2012 R29 this morning having removed the anti-freeze last week. We were motoring to my usual docking site this afternoon after 2 hours of cruising at 8 knots I slowed to 4 knots and within a minute or so "Over Heating" alarm came on showing a reading of about 250 and oil pressure of almost nil, checks showed an engine that didn't appear to be very hot, discharge water only warm, the metal fitting from the engine block felt cold, over flow bottle of engine coolant was at it lowest level, oil level normal and not hot, there appeared to be plenty of water in the intake filter. After making all these checks we continued the final half mile to the dock. An hour or so afterwards i ran the engine at 2000 rpm for 20 mins. or so and temperature remain about 180 and oil pressure was normal.. The impeller was changed last August, the present reading is 317 hours. Does this sound like an instrument problem or could it be an impeller problem. Has anyone else had similar experience.
Many thanks for any help Dave.

 

[Boont Boater]

Bad sensor?

 

[dante3756]

I have a 2011 R29 with same engine and had some overheating issues early on. Mine was caused by a leak at the water heater, resulting in lost antifreeze. You didn't mention that you had checked the antifreeze level by removing the cap located under the entryway to the cabin. That's the only valid way to check antifreeze level - not by merely looking at the overflow bottle. Remove the cap, stick your finger into the opening (you can't see it since it underneath fiberglass). If your finger comes out dry, that's your issue. Not likely a sensor issue. Most likely issues: Low antifreeze, bad impeller (I change mine every year), or something stuck in the thru hull fitting. There's also a thermostat in the fresh water system that should open at 192 degrees. But these rarely go bad and are a bitch to change out. I actually checked mine using boiling water - worked fine.

 

[knotflying]

First, never check your antifreeze level after the engine has been running. It must cool down considerably before you remove the cap. Secondly, it seems odd that you had two separate issues going on. Low oil (did that alarm sound) and high temp. On the 4BY2 - 180 and 150 there was a service bulletin where the software was up dated because of erroneous readings on oil pressure. Nothing about erroneous high temperatures though. It does seem like a temporary glitch in your ECU. Check your wires from the engine battery to the ECU and to the engine. These units are very susceptible to erroneous alarms because of poor ground bonds. I ran a redundant ground directly from my engine battery to the engine block and I always make sure that the leads from the battery to the ECU are clean and well connected.

 

[Irish Mist]

I had mine ( 2011 R29 ) do this a few years ago after launching from my trailer.. Not sure where the antifreeze went, but after I removed the rad cap, I was able to add a substantial about of antifreeze. Do not know why it was low or how it got low but no issues since. After that incident, I check it periodically by removing the rad cap when the engine is cool.

 

[D & C M]

Thanks to everyone, hopefully I have found the cause of my over heating problem. Low antifreeze, but where it went I don't know. The engine took almost a gallon of antifreeze and so I will have to wait until tomorrow for auto suppliers to open.
Dave

 

[knotflying]

Check all your hose clamp connections. The most difficult at the two at the back of the water heater. You can gain access by removing the base panel in the head sink cabinet and do that by feel. I have found that another problem area is the heater unit by the helm, which is heated from the engine coolant. Those clamps tend to loosen up as well. Leaks are often not detected there because the coolant will run down to the bilge area. Also check the hoses that come off the engine port side that run to the water heater. Then there are the hoses off the head exchanger elbow below the fill cap on the bottom.
I have also had issues with the drains and replaced one. There is one that is visable on the port side of the engine and screws into the head exchager side and the is also another visible below the turbo and back at the heat exchanger.

 

[Kaisardog]

OP stated "over flow bottle of engine coolant was at it lowest level..." These yan mars are very sensitive to proper coolant level. keep that 'overflow tank ' at the high line by checking it and topping it up before your daily run . and if the fluid is to the bottom of the overflow, it's wise to check the fluid level in the main radiator tank.

 

[Craig]

Dave only use yanmar coolant juice or do as I did and go to ur BMW dealer and get their coolant juice


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[R Baker]

Coolant for 6BY2. Some years back Mack Boring (a large Yanmar dealer) put out a bulletin that included Havoline Long Life Coolant as an acceptable coolant for this engine.

 

[knotflying]

Prestone long life is good also and approved.

 

[ttlmac]

I have to re-tighten the connections to my water heater each year in the spring. I think the very hot antifreeze temp when underway causes the connections to expand during boating season. In the winter it gets real cold (at least here in New England) and the connections loosen enough that I seep anti freeze. I always need to add some in the spring. Was the same for my R25 as it is now for my R31.
Tom
Indian Summer II

 

[captstu]

The Yanmar set up in the Rangers is especially prone to trapping air in the line to the cabin heater and the line to the hot water heater.

This can happen when the antifreeze is drained and refilled without removing the air. There is a special process to remove this air, however the easiest way to do it is to fill the any freeze and run the engine for a few moments and refill the antifreeze.

This will get most of the air out. After the engine gets hot and cools down some of the rest of the air will come out and anti-freeze will be sucked from the overflow tank.

This is normal.


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[paulbugs]

I launched my 2012 R29 this morning having removed the anti-freeze last week. We were motoring to my usual docking site this afternoon after 2 hours of cruising at 8 knots I slowed to 4 knots and within a minute or so "Over Heating" alarm came on showing a reading of about 250 and oil pressure of almost nil, checks showed an engine that didn't appear to be very hot, discharge water only warm, the metal fitting from the engine block felt cold, over flow bottle of engine coolant was at it lowest level, oil level normal and not hot, there appeared to be plenty of water in the intake filter. After making all these checks we continued the final half mile to the dock. An hour or so afterwards i ran the engine at 2000 rpm for 20 mins. or so and temperature remain about 180 and oil pressure was normal.. The impeller was changed last August, the present reading is 317 hours. Does this sound like an instrument problem or could it be an impeller problem. Has anyone else had similar experience.
Many thanks for any help Dave.

 

[Bart Keil]

Had same issue. After three trips to service they found radiator cap had a crack in the gasket. When at temp, antifreeze went to bilge and got pumped over. One new cap and we are good to go!