Frequent Yanmar Warning Buzzer?

[SeacretSailor]

Hey guys,

I have a 78 C&C 29 with a Yanmar 2QM15 that runs great and I keep it very well maintained. I was a trailer-sailor (outbaord engines) who converted to a bigger boat only 18 months ago, so I'm still learning diesels.

Here's my problem/question: Every so often, when I'm motoring for at least 30min, I'm getting a warning buzzer on my cockpit Yanmat panel. It's the middle light, which according to my owner's manual the three lights read: Oil - Water Temp - Charge, so being the middle light, it must be a water related warning. It did it again today while motoring back to dock.

When it goes off, I have found:
1 - Plenty of water exhaust out the transom, no change or lack of water coming out.
2 - With the motor in neutral/hatch opened, there's no excess heat or smoke
3 - Water pump look good and pumping
4 - The water intake looks OK when I dove underneath.
5 - Oil levels are good and filled correctly

I'm stumped and not sure what else to check? I assume if it's the water light, that it's a cooling issue, but how can that be if plenty of exhaust is coming out? Having checked the strainer yet, so maybe that needs inspecting? My thinking is: If enough water's coming out then enough must be coming in and circulating?

Any thoughts on what else I could check?

Thanks
Kevin B.

 

[Ken13559]

maybe its the wiring insulation thats wore and touching ground ? maybe the temperature switch is faulty ?

 

[capejt]

one more thing to check

You did a pretty thorough check out, but there is one thing I can think of that you didn't mention. Check the thermostat. I had a similar situation (with the same engine) and changing the thermostat solved it for me.

 

[Surveyor]

Fresh water cooled? Have you bled the air from the water heater loop?

 

[saltygator]

If it's fresh water cooled the heat exchanger could be scaled up... The circulation pump could not be circulating the prestone through the engine too. But I would start with the thermostat. When the horn goes off, check the tempature of various parts of the motor. You should be able to figure out if the thermostat if flowing water. Also, changing the thermostat certainly won't hurt anything.

Good Luck,
John

 

[Deleted member 78819]

You didn't mention checking the fresh water side so I don't know if you have a heat exchanger like my Yanmar 2GM20F but the fresh water side needs to be changed annually with the appropriate anitfreeze and antirust additive. If you don't have a fresh water system then I'd replace the thermostat.

 

[SeacretSailor]

Thanks for the suggestions - I never thought about the thermostat, being an outboard guy. I'll change it next weekend.

Forgive me for another newbie question, but I assume that my engine does not have an internal cooling system nor a heat exchanger, right? That's because on my flywheel, the 2 belts only drive an alternator and a water pump. I've seen photos of other Yanmars and the alt belt also drives another pump on top of the engine? I guess that's for an internal water circulating pump? So since mine doensn't have that I only have external cooling, so that should narrow it down to the thermostat.

Wish me luck!
Kev

 

[Hermit Scott]

Check the actual temperature instead of relying on the buzzer. That is where I would start my trouble shoot.
There will be a heat exchanger, that's how you know if you have fresh water cooling. The tube from the seacock bringing in water will go to a heat exchanger instead of directly into the block.

 

[Stu Jackson]

...I assume that my engine does not have an internal cooling system nor a heat exchanger, right? That's because on my flywheel, the 2 belts only drive an alternator and a water pump. I've seen photos of other Yanmars and the alt belt also drives another pump on top of the engine? I guess that's for an internal water circulating pump? So since mine doensn't have that I only have external cooling, so that should narrow it down to the thermostat

Kev, on many engines the raw water pump is not driven by the belt, but rather is mechanically driven being bolted directly to the engine, and the freshwater (coolant) pump is the one driven by the belt.

Also, you should easily be able to see the heat exchanger, it's usually a cylindrical tube on the back of the engine, Hermit's exactly right.

Find out more about your engine at www.marinedieseldirect.com. Download and printout the diagrams and parts lists.

I don't have a Yanmar, we have a Universal, but the concepts are the same. All of us started out not being diesel mechanics, but most of us became the best in the field: namely, our own! Who else ya gonna trust more?

 

[kloudie1]

Sorry to hear ya having problems, Kevin. Pretty sure your engine is raw water cooled, and doesn't have a heat exchanger or a secondary cooling loop. Thermostat sounds like the next thing to check/change.. The guys up at Labourde Products in Covington 985-892-0107 can do a mail order . They are the major Yanmar distributor for the area. http://labordeproducts.com/

 

[druid]

Well, usually the Yanmars that are FWC have an F at the end (2GM20 vs 2GM20F, etc.) so if you have a 2QM15, not a 2QM15F, it's raw-water cooled. Still has a thermostat, though. I am surprised the newer Yanmar even COMES as RWC - most newer engines are all FWC. And unlike the Universal, the heat exchanger is inside the exhaust manifold so it's not easy to spot. But you're right - both the freshwater and saltwater pumps are run off the belt, so if there's only one (the lower left one) it's RWC.

druid

 

[Jeff B.]

I've got the same engine and I'm pretty sure the FWC on mine was an aftermarket addition.

We had the same problem you describe though SeacretSailor - inexplicable overheat alarm. The initial problem was that one of the flanges on my fresh water impeller broke off and wedged the pump to a stop. After clearing the blockage, everything SHOULD have been fine but we got the alarm again after about 10 minutes of motoring.

Of course this all happened 10 miles from the Columbia R. Bar right as a squall brought us 40kt winds and 7ft waves. What a wonderful time to be down below troubleshooting an engine and trying with all one's cunning to not lose any of the essential screws or parts you've just removed!

Anyway, my eventual fix to the problem originated from one of three potential tactics:

1) Allowed the freshwater system to burp itself (ran the engine with the radiator cap off)

2) Unseated and re-seated the thermostat (most likely that it just got stuck somehow)

3) Banged on the engine in strategic locations with a hammer (an equally plausible solution, and often employed)


Really it sounds like the collected wisdom here already diagnosed your problem. Just wanted to commiserate.

 

[Cayennita]

Let's not forget that when the alarm gets wet because of rain or in some cases heavy mist/fog/etc. the alarm will go off and on sending you into a panic mode. I had a Hunter 35 and now a J-36 with raw water cooling. I changed the alarm in both cases and never had a problem after that. I did all the same things that have been mentioned above. Buy a 12 volt universal alarm from a car parts place and install it away from the panel where it will stay dry. That is, if everything checks out and you run out of ideas.
In my 51 footer I had to rewire from the sending unit to the panel. Could not find the problem, but determined that it was the wire by using a temporary jumper.

 

[Benny]

An electric short may act the same way as a sending unit by closing the circuit and activating the buzzer. Check the wiring harness from engine to control panel for chafed insulation on the wires.

 

[filthy liberal scum]

the problem is most likely blockage of water passage

I've had an o"day 30 with this same engine for over 20 years.
first, yanmar only offered this particular engine in the raw water cooled version. i had at one time had this same problem. here's what i found. at the rear of the engine there are a couple of openings in the block and the head that allow the cooling water to circulate through the block and head. there is a housing like piece that the sending unit is screwed into on the rear of the head. here's what happens. since its raw water cooled rust builds up in the water passage between the block and the head thereby reducing the flow and creating a hot spot thus tripping the alarm. this can become a major problem. with this hot spot it can become hot enough to crack the rear most valve seat. if it does you are shit out of luck as it can't be repaired and its a new head time. temporarily here's how to fix the problem. remove the housing that holds the sensor. (two bolts) then get a very stiff wire such as a 1/8" welding rod, bend the end with a 90deg elbow that is about 2 or 3 inches long. then start poking in a downward direction opening up the passage way. i will say that this isn't an easy thing to do, since you have to get in some real contortionist ways to access it. you will also need a good light to be able to see. you will not see any reduction in water flow out the exhaust since the water is flowing as normal in the rest of the engine. this problem will be a recurring issue with this engine in the raw water configuration. i solved this issue when i rebuilt my engine by installing the aftermarket freshwater cooling system. unfortunately this won't be an easy thing to do since sen-dur no longer manufactures it for this engine, but they might have one that can be adapted.
this is a good engine except for the fact that they usually don't wear out, but destroy themselves internally from rust and corrosion. another issue with this cooling system is that the water passages in the exhaust manifold become clogged with rust and corrosion. thus destroying it. then you really are ****ed. yanmar no longer sells the manifold. i don't think that the manifold for the 2GM will crossover fit.
i would remove the exhaust manifold and get it cleaned out. i boiled mine out with radiator cleaner and did a lot of poking to get it cleaned out.
this is on of the big headaches of a raw water cooled engine that has been out of production since 1980 or 81

 

[Jumpstart]

A couple of other things to check. Raw water strainer- I had similar problem and found some sea weed in the strainer. Not enough to block flow but enough to reduce it.

 

[SeacretSailor]

Thanks for all the great suggestions - I changed the thermostat (quick & easy) and it was corroded. While up to my elbows in the engine, I changed the secondary fuel filter, bled the fuel lines and checked the engine block zincs. I ran the engine and it ran perfectly! Thanks again guys!
Kevin