I recently did a complete overhaul on the pony engine of my graders D311 motor. Starts and runs great but the main engine is transferring coolant from the radiator to the main crankcase. The oil cooler is blocked off so that takes it out of the list of possibilities. One day while cranking with the pony engine clutch engaged, it started gushing coolant out of the radiator cap. I’m thinking head gasket may be the culprit. Any ideas out there? Wouldn’t be related to the pony mounting gasket would it?

probably a bad head gasket.

-do you need to add coolant at all? every so often? even a litre or two?? and no noticeable leaks? or signs of where it could going?

- I would bet head gasket...
-have an old (1965) case diesel tractor and only ran in the summer, but always had to add a little coolant every year, no big deal....until suddenly it was a big deal, started puking coolant out the rad cap
-tore the heads off and you could see where the head gasket was not sealing 100 percent, and the combustion chamber was clean and a different texture, so it had been seeping for years..

It could also be bad liner seals. There’s o-rings on bottom of them that separate the coolant from running down into the crank case, if they have gone bad it’ll transfer coolant pretty easy into the crankcase.

good point Nathan, yes the liner seals (o-rings) can easily pass coolant to the crankcase, esp on older engines, my guess is they get hard and brittle over time with heat cycles etc..

-another thing i remember with my tractor head gasket issue, there was sometimes an odd mixture on top of the coolant, below the cap in the rad.....heard it called "black mayonnaise"...not sure what it is....maybe byproducts of combustion entering cooling system...just another possibility to watch out for

yes heat and age deteriorates the orings on the liners. isnt there a special method of checking the liner protrusion using a dial guage so you adjust it using shims.

trainzkid88 wrote:

using a dial guage so you adjust it using shims.
 

Not according to my D8, D6 and 944 workshop manuals all they say is to make sure the liner protrudes slightly above the block. I assume you mean a dial indicator but you would be better off using a depth micrometer either way it would not be the cause of the water in the oil issue.

Isn't there a water port though the bottom of the pony block?

Did you replace precombustion chambers?

yes there is a coolant passage through the bell housing into the pilot engine block.