D2 Pony Motor over heating

Better check the thermostat and water pump to see that they are operating properly. What is the serial number of your 3J?

3J3016SP is the serial number. I need someone to explain how the water flows around the pony motor and the diesel engine so I ge the big picture. I have the themostat out still in the housing so I can test it for you if you tell me what to do. I thought even if the themostat does not get hot enough to open the diesel water pump would still circulate the water through both the engines to warm up the diesel and then open up to the radiator if hot enough. Does water come in through the bottom of the diesel engine into the bottom of the pony motor and go out through the top of the pony motor back into the diesel head? How can I see if the water pump is working also like you suggest? If need I will pull the pony motor but would like to advoid that.

Hi David,
Yes the Water flows from bottom of the engine water passages around the cylinder walls etc to the bottom of the flywheel housing up through pony and into the head of the diesel along the top of the head to the water pump into the top upper elbow and hose to the radiator down on through to the lower radiator tank then through the lower water pipe then the water pump and the sequence begins again. When you are cranking the diesel with the compression release lever in the 'Run" positon is the top area of the diesel engine block nearest the pony getting wrm at all. The heat starts there and works it way to the front of the block when spinning the diesel.

After we tried to start the Diesel engine in the run position, we checked to see the Diesel engine was warm and it was still cold
but the cylinder it seem by the pony motor was a tiny bit warm and the pony motor was shut off because it was burning hot.

Have you flushed the diesel block real good? Disconnect the upper and lower hose and or pipe from the radiator, flush the diesel block real good with water and air pressure if possible. The pony water passage into the Diesel head and the lower bellhousing passage could still be plugged. You will need to remove pony and check these. I would check the whole cooling system from radiator to pony. Get a servicemans reference book if you don't have one. Without one of those, your lost.

I think your pony motor has an air bubble.

Later models had an air bleed and there was some information on this board several years ago about where to drill to add one to the older models. The D2/D4 pony motors don't have their own water pump and as a result, an air bubble stops the flow through the pony quite easily. Of course it is entirely possible that you still have sediment blocking the circulation which will be evident once you remove the pony from the clutch housing.

I know the D311 pony I have the most experience with would get very hot if I forgot to bleed the air from it.

There is a cross over cooling passage cast into the bottom of the pony block that does not have alignment that allows roding for cleaning without removing the pony and working from the bottom. Even then there are offsets to the passage that makes cleaning difficult. Also a possibility that sediment (that turns into cement) may be built up in the passage that goes from the main engine, through the flywheel housing and up into the bottom of the pony block.

airlock, besure to bleed 1st, or, rust filled passages in the heads. pull heads 2nd and check 4 rust, easy todo and u can use the gaskets over.

good luck.