M 25 XP runs too cold

[Hayden Watson]

I cannot get my M 25 XP to run hotter than 140º. I have tested the thermostat and it opens at 160º. I bought a new 160º thermostat and it too will not get the engine to run higher than 140º. Any thoughts?
The engine is normal factory setup with the by-pass routed through the water heater heat exchange. When I start the engine cold, the water reservoir and top side of the thermostat housing heat up faster than the block and bottom half of the thermostat housing. If I hadn't just put the thermostat in I would swear that there wasn't one installed.

 

[Stu Jackson]

Have you cleaned the temperature sensor connection? Have you checked the gauge?

 

[mortyd]

you actually asked a question i was about to. my temp stays at 140 when it was usually 160, but this year has not been a hot one so far, so i'll wait and see. 140 isn't all that cold.

 

[Hayden Watson]

Have you cleaned the temperature sensor connection? Have you checked the gauge?

I have been chasing all sorts of temperature issues this year so I got a non-contact infrared thermometer. The new infrared and the gauge agree. The strange part is that the water reservoir and discharge side of the thermostat housing gets hot faster than the block and inlet side of the thermostat housing. These should both stay relatively cool until the engine warms up fully and the thermostat opens. I got a reading of 130º on the reservoir when the bottom of the thermostat housing and the water pump were only 90º.

Mortyd: Diesel engines are compression ignition engines and do not like to run cool. They tent to build up carbon if they are not run hot enough which is why I want to find out why the temperature is not up where it should be. Kabota actually makes the Universal block and they want you to use a 180º thermostat but that can cause salt deposits in the raw water heat exchanger. The air and water temperature should not make any difference.

In prevous seasons cool running has not been a problem because my heat exchanger was partially plugged. When it got so bad that I needed to clean it out due to over-heating I found that now it wouldn't run hot enough! :bang:

 

[Hayden Watson]

Here is an update on this frustrating problem.

I have changed the thermostat to a new 160º Universal thermostat and it still will only run at 140º at full speed. I have checked both the new and the old T-stats in a pot of water on the stove and they both start to open at 160º and are fully open at 180.

When I check the temperature of the different parts of the cooling system, all are at the same temperature with the exception of the outlet of the heat exchanger which is about 20º cooler.

Any thoughts on things to check would be greatly appreciated.

 

[BrassRat]

Based on what you've done so far, logic would indicate water is going around the thermostat somehow.

 

[Hayden Watson]

I have come to the same conclusion but cannot figure there it would be going. If I understand the cooling system correctly the flow the basics are...
1. Water enters the water pump by one of two lines, either warm water from the by-pass line or cold water from the heat exchanger.
2. The water pump pushes the water into the engine block where it is heated and exits at the thermostat housing. If the water is less than 160º the thermostat is closed and all of the water leaving the block must go through the by-pass line (which in my case is connected to the water heater and a cabin heater). If the temperature is more than 160º some of the water will be directed to the reservoir at the exhaust manifold.
3. The water that is sent to the exhaust manifold must be replaced so the same amount of cold water is then pulled back into the water pump from the heat exchanger.
Am I missing anything and is there any way that water can flow other than what is described above?