Hello Folks, 
My friend has a D9G, not used due to over heating, after sitting for 2 years we started it, fired up straight away, no priming etc, no abnormal sounds runs smooth with diesel knock a little louder on front half of engine.

We replaced the Thermostats/Regulators  76'C and there seals, gaskets and ferrule.

On low idle engine warms slowly as expected not moving implements, gears, etc, has no bubbles in top tank of radiator, pipes hoses etc warm as you would expect, bypass seems to work as warmth is comparable to other lines, including after cooler.
We lifted RPM approx quarter throttle then within a minute the temp rises very quick to half on gauge and climbing, the gauge sensor is mounted in the coolant manifold (I think as per factory) just before the thermostat/regulator housing.

Return line to top tank stays warm only at tank, closer to thermostat/regulator housing the hotter it gets towards red hot to touch, as expected for flow direction.

At this time we stopped the engine, after checking lines on both sides and across the front of the engine all are pretty much roasting, bottom radiator line is cool to touch ( I think this would be correct for circulation), top radiator line is warm only at tank everything else hot.

We did find a couple of drips out of water pump (guessing witness hole) on engine block side of water pump (not able to see by eye), from my past experience this would mean issue with pump itself (seal leaking), possibly worn bearing to causing seal to leak and possibly impeller to rear plate gap to enlarge to allowing bypass of coolant instead of pumping. The leak was found when warm/hot stopped engine, leak stopped when engine was running.

I am suspecting water pump bearing, seal, impeller and rear plate worn and or corroded.
Any input would be greatly appreciated, 

Thank you
Jamie

The water pump would be a good start, also engine oil cooler may be plugged. Sounds like a coolant circulating problem.

Hi, Busso20.
It would not be surprising if the temperature gauge shot up when you brought the revs up if the engine had been idling long enough to warm up to thermostat opening temperature.

Likewise, it would not be surprising if the return pipe to the top of the radiator got hotter down low than up near the radiator - - - - in the VERY short term - like immediately after the thermostat opens. BUTTTT, the two ends should equalize fairly quickly. In theory, the bottom of the radiator and associated pipes should be cooler than the top but certainly not 'cool' when everything up above is HOT. Leaves me wondering about the condition of the tubes in the radiator core.

Also, the 'serial #' that you have quoted for this machine leaves me wondering. I thought that ALL of the D9Gs were 66A series.

But what would I know? I'm justa 'pore, dumm bulldozer operator'.

Just my 0.02.

28Hxxxx is the s/n for the hydraulic control unit on the D9G
Cooling system expectations....
 

Deas, OM, Rome K/G,
Thank you,
I will dig in to the coolant pump and see the condition inside, Thank you for the info on the hydraulic control to confirm the numbers, we will look for the 66A to be sure.

What's the pressure situation? What does the pressure gauge show? could the pressure relief valve have anything to do with it?

GG we ran it with out the cap on to check for bubbles and coolant temp as well just to be sure with finger

It may look like mine did when i took the top tank off the radiator after many years of no green potion.





Serial number should be here.