G'day all I have a D4 6u with a d315 engine. The engine starts and runs well no smoke it doesn't burn oil nor does it get hot. But now I am losing water and getting water in the engine oil do you have any idea where to start looking for the problem

Could be liner seals or a pin hole in a liner. If a prechamber is leaking you will see bubbles in the radiator tank and a white/gray exhaust color from the stack. You could pull a side cover and take a mirror and look under each liner to see if coolant is dripping. Another possibility could be a crack in the head to the push rod area or a rubber grommet under the head is bad.

I will add an oddball that I found on a D318 engine. I washed the sludge out of the liner lower seal area and created a FAST leak but I washable to seal it up with DIKE brand stopleak by mixing up a couple bottlesvwith maybe 1/2 gallon coolant, pumping it in and letting it settle overnight before filling the system with coolant and running it and changing the oil etc. I had drained off all the water I could get from the bottom of the oil pan prior to starting!

In summary, I don't think liner o-rings are a big deal to seal up. There is a labyrinth of tight spaces with the seals and gravity tends to settle solids into the area anyway, so it should be pretty easy to get it to stop leaking coolant. A liner that is pitted through below the compression rings travel would be more difficult but maybe not impossible to plug up temporarily.

Fast forward 2 years and i began to see moisture in the crankcase again. I was assuming it was time for a real fix or junk the dozer more likely but I decided to retorque the head because it had an obvious seep along the head gasket on the right side. When I took the valve covers off I found liquid coolant in there and a rusted out "freeze" plug which there are several down the center top of the head, some external to the rocker boxes and some inside under the rocker arms. I am certain the D315 has the same design, just a shorter head so fewer plugs. I was able to poke a screwdriver through a couple of them and drove a sharp punch through the rest to pry them out and replace.

Thanks that helps a lot. Not to sound stupid but do I check the liners through the side plates on the motor

You can look for coolant dripping down by taking off the side covers and then putting pressure on the cooling system. You cannot access the cooling water jacket space around the cylinder sleeves until you remove the head, connecting rods and pistons and then pull the sleeves. At that point you always find there is a layer of sediment and scale in the bottom that falls out when the sleeves are removed.

My leak was caused by jetting water into that area through the block drain hole, so I washed that sediment away from the base of one or more sleeves. It was leaking so fast I could watch the water level dropping in the radiator top tank! I had nothing to loose except the cost of a couple bottles of DIKE so I tried it and it worked very well. As I said, when I thought it had failed 2 years later, turned out it was the freeze plug in the head. Fixed those and the tractor ran another couple years until the next owner let it get diesel in the oil AND kept running it until it threw a rod through the side of the block.

Just a couple caveats about using stopleak.....I had just rodded out the radiator core so the stopleak didn't plug the radiator. I put the DIKE mixture in through the same hole I had jetted the water in and washed the sediment away so it had perfect placement. It was a BIG leak though!

I have used BARRS LEAKS in other situations but when the coolant is mixing with the oil, the DIKE gel seems safer.
i would not hesitate to give it a try. The cooling system on most old CATs runs at a low enough pressure it doesn't take much to plug the leak.

I pumped the stuff into the block instead of adding to the radiator because I was very confident where the leak was and it was so fast I could have never run the engine to distribute the stopleak around the engine if it had been added to the radiator. I had water shooting out the dipstick tube when I finally figured out what had happened!