onan mdjf 15 kw gen. thermostat

[workingonadream]

my gen is running hot. cleaned heat exchanger, but still ran hot. checked thermostat and saw that it was opening around 190-195. i pulled it out and saw it was a 180degree which to me seems too hot.does anyone know what thermostat should be in there. i would think a 160 is more appropriate.2 diff cummins dealers gave me 2 diff part numbers.one was 309-0054 which is supposedly a 150 degree, the other dealer told me309-0270 but could not give me the degree.my gen model number is mdjf3cr2268aa serial L780381681. i just want to get the correct one because it is 150 bucks. thanks.

 

[labrador]

Cummins engines run warmer that detroits. Mine run around 195 and I know George's gen (Incentive) with a Cummins also runs between 195 and 200. George feel free to chime in if I mistated the facts.

 

[workingonadream]

thanks for the reply i would like to see if george's gen runs at the same temp as ours. today i finally found an old timer at cummins that knew how to look up parts for our old dinosaurs. he said i should have a 150 degree stat in that gen, and since i dont run during the cold seasons i am tossing the 180 stat and putting in the 150.my best guess is the owner before me ran in the cold season and neede the extra degrees. again thanks for the reply

 

[Fanfare]

My old 12kv ran steadily at 180* in all sea water temperatures. While you don't want it to overheat, diesels are more efficient at the higher temperatures and the lube oil will not get as much condensation in it. Check your owner's manual for the correct thermostat.

 

[labrador]

I would PM George. I know he's running all around the country this month however he still lurks here. I remember him saying one night when we had a few adult beverages on his back deck or maybe it was mine, that his cummins engine gen set which is a 20kw onan, runs constantly at around 200F and had at that point just under 4000 hours. As I said we had a few pops but that info sticks in my mind.

 

[bwellen]

I have a 1974 MDJF thats running a bit hot. I laser gunned the coolant tank that the heat exchanger runs through and it read 200 degrees. What is the normal operating temperature for these? Does anyone know where i can find a thermostat for this old boy? Pictures attached...

 

[whoover]

Hello, if you have a part number you can try Onanparts.com. I've had luck in the past with them for some things.

Walt Hoover

 

[bwellen]

Thanks Walt. I was able to locate one, but am now struggling with where it is actually located on the generator. I have looked through both the parts manual as well as the service manual but it remains unclear where the thermostat is located. Any ideas? I have my eye on 2 spots:

1) on the top near the heat exchanger



2) on the back on the engine block (2 hoses from the heat exchanger that connect to a "T" that goes into the engine block.

 

[whoover]

I'm just guessing but I will say under the housing in the first pic. I know that the thermostat on my MDJE 7.5 is small, about 11/2" diameter but it is located under the coolant tank at the block.

Walt Hoover

 

[bwellen]

No luck under that housing, took it off and looked at it last night. Is it possible that there is no thermostat on my generator?

 

[oscarvan]

No luck under that housing, took it off and looked at it last night. Is it possible that there is no thermostat on my generator?

Or someone took it out because it was running warm?

 

[whoover]

From what I can see from the parts manual the thermostat is between the expansion tank and block but the diagram seems to change from spec to spec.

Walt Hoover