1610 Erratic Temperature

[superk6]

Just crank my 1610 after it had sat for 4-5 months. The air temp is in the mid 60's. It started with no problem. I let it idle at a 1200 rpm for a few minutes and the temp gauge just barely moved off of the "C". I then ran the rpm's up to about 1800-2000 to give the motor an opportunity to get up to operating temperature as it normally runs closer to the middle of the range of the gauge when under load. The temp gauge slowly moved up until it hit the midway point where it stopped for a couple of minutes. The I noticed it went up to about the 3/4 mark then dropped quickly back to the midpoint. However, it quickly started climbing and passed the 3/4 mark before I shut it down.

Can anyone clue me in on what might cause this? The radiator fins and screen are both clear. I understand that this little diesel does not have a thermostat. It is an older gray market 1610 with less than 1,000 hours.

 

[winston1]

Sounds like a sticking thermostat to me but Hoye doesn't even show one for the 1610. Maybe you don't have one??

 

[superk6]

I read elsewhere in this forum that the1610 engine does not have a thermostat. My visual inspections (today and in the past) did not reveal any location for a thermostat. It appears that the hoses connect directly to the engine without an accommodation for a thermostat. However, I am certainly not an expert on this.

 

[normde2001]

Is it really overheating or is it not?

 

[careyo63]

My Parts show no Thermostat either. Temp sending switch with a Gauge though. TS-1470. You may want to give the Radiator a good flushing if you haven't recently. Air Pocket?

 

[FleetMan]

If you have an IR temperature gun, take some readings at various points on your engine to verify if you do have a problem.

 

[rScotty]

The old thermosiphon type Yanmars would overheat and show irratic temps when going down a long steep slope. Is yours parked nose down?
rScotty

 

[superk6]

It is parked on level ground. I read on the Hoye site that these thermosiphon type systems do not perform well if the antifreeze mixture is over 25%. I have been using a 50-50 mixture. I had not experienced any problems before using this mixture. I will flush the system and refill with a 25% mixture when it warms up here again. It was 65 today but is supposed to be below freezing for the next week. In the meantime I will by a mechanic's thermometer so I can get an accurate reading. Could be the sending unit or gauge is faulty.

 

[California]

Harbor Freight's $12 Non-Contact Pocket Thermometer is all you need.

Long ago I posted my observations of the YM240 on here. As I recall after working hard, I saw something like under 200 degrees at the top of the block and radiator, 165 at bottom of the radiator and the oil pan.

 

[superk6]

I will get that thermometer. Thanks for the info.