I picked up a JD 410C about 2 weeks ago. When I bought it the previous owner told me they stopped running it because it was leaking oil into the coolant system. Apparently Deere Told him it was probably a failure in the oil cooler. The radiator had so much oil in it it wouldn't even drain. I replaced all the gaskets and o-rings in the oil cooler, pulled the radiator and had it flushed, pulled both thermostats and used a pressure washer to flush the block until the water ran clean. The heater core is bypassed with a hose right now. When I put it back together I put on a new 7psi cap. I was running the machine for about an hour today and stopped to look at something and saw oil had sprayed out of the radiator overflow and all over the front end. None of the hoses were more than warm to the touch so I was able to pull the rad cap and of course there was a ton of oil in the radiator again. There was some oil left after it was flushed and I haven't flushed it again yet. I'm just looking for ideas if it's still residual oil in the system or a bigger problem. There was no water in the oil when I changed it and none in it now.
Did you replace the oil cooler its self?
No, just all the o-rings and gaskets. I didn't notice any cracks or anything but didn't think to look too close. One of the o-rings between the cooler and the block looked like it was split
The core in the cooler is probably bad. You can bypass the cooler by putting a piece of hose from the water pump outlet that goes to the bottom of the cooler and connect the other end to the fitting on the engine block and remove the pipe plug from the bottom cover on the oil cooler and see if oil comes out of the hole the plug was removed from. The oil cooler is really the only thing on that engine that could cause oil to enter the cooling system. It would probably be ok to run the machine with the cooler bypassed for short periods but if it'd pretty decent machine it's a good idea to replace the oil cooler core. The prt # for the core is RE31089.
I'll give it a shot. At least the core isn't horribly expensive and available