CD 25D Yanmar temperature alarm

[n5ama]

I made it to the boat and reinstalled the mixing elbow. I fired the engine up with the new thermostat and my alarm came on again in +- 2 minutes. I still had the same amount of water discharge as before.

The only thing left was the pump impeller so I checked it and it looked ok (changed it less than a year ago). I noticed the instructions that came with the Yanmar kit had the direction of pump rotation as clockwise and I had the impeller with the pump rotation CCW as per the manual. I reversed the impeller just to be on the safe side not knowing which one to believe. Which is the correct pump rotation, the instruction in the kit or the manual.

Anyway, I fired it up again and got the same alarm in approximately 2 minutes.

The only thing I can think midget be the problem is a faulty temperature sensor.

This cooling system isn’t rocket science but it is giving me fits. What do you think?

Thanks,
Tom

[Frenchy]

The temperature sensor is a prime suspect, I have to agree. Did you try putting your hand on top of the engine as one
of the other posters suggested or perhaps use an infrared sensor?
If the engine really is hot, a possibility is a faulty thermostat. It happened to me once- a brand new thermostat failed to open
when I put it in a pot of boiling water.
If the engine isn't hot, then it's the sensor. Good luck tracking this down.

[n5ama]

Hi Jean,
Thanks for the quick reply.

The warning alarm started in the 2 minutes from cold at 1000 rpm (the head was barely warm). I didn’t measure the temp with the IR sensor because of the alarm (makes me nervous with loud warning noises) and I didn’t feel the engine had enough time to normalize to operating temperature.

I’ll order a sensor today and hopefully in the next two or three weeks, I’ll be able to return and install the sensor.

Have a great week.
Tom

[Brent]

I am having the same issues with my Yanmar 1gm on my cd25d as Tom, idiot light and alarm are going off. Run the engine for 10 minute in gear and the alarm goes off. Changed the sensor switch, changed the battery, checked the wiring connections, when the alarm goes off used the infared laser and the temp on the egine never gets above 135 degrees. temp of the water coming out of the exhaust is under 100 degrees. Is changing the thermostat my next try? I wanted to put a tee and a nipple in the engine block and put the sensor on one side and a temperature gauge on the other but the threads are metric and I haven't found where I can get metric theaded tee and nipple? Any thoughts would be appreciated.

Brent

[Frenchy]

Hi Brent - I suspect that the problem may be oil pressure, not temperature. The alarm on the 1GM is connected to
both sensors, as I remember. Check oil level, change if necessary. It wouldn't hurt to check the transmission oil
level also, while you're at it. The problem could be a defective oil pump, but I think that is very uncommon- as
they are bathed in oil and pretty robust. Perhaps the oil pressure switch is defective? Anyway, good luck - Jean