Go BottomOil in the water
 | St Albans
Join Date: May 2004 Posts: 1 St Albans, NSW 
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2004-05-17 86184
I have a 10 yo Kubota L355 SS 4wd 35 hp tractor with rops qr-front end loader and generally use it for slashing and soil/rock movement
I have been getting oil in the water - the forst time - i replaced the head gasget and did a general top overhaul - everything looked OK
a month went by and once again oil in the water - so off came the head and had it tested - all ok so back together and another month of service - and you guessed it - oil in the water - no sump contamination - any ideas?
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| hardwood
Join Date: Dec 2002 Posts: 3583 iowa 
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2004-05-17 86185
I don't have any experience with Kobota engines, so I'll just give you some guidelines I've learned with past experiences with oil in the coolant. Being oil pressure at operating speed is greater than coolant pressure there has to be somewhere that a crack has developed or a seal has failed. If this engine uses a water to oil oil cooler they can develop a leak and let the oil pressure force oil into the coolant, those can be pressure tested. I had a Ford gasoline engine once that had a hole drilled too close to an oil gallery, over time a leak developed into the water jacket of the engine. I don't know if your engine has wet or dry cylinder liners, but usually if a wet sleeve cavitates or a lower sleeve O ring fails the coolant will go to the oil. Your water pump may be gear driven from the timing gear set, I've also had this happen that the seal on the shaft of the water pump will fail, but again the coolant will go to the oil. I'm only giving you general possibilitys that apply to most engines, not a real answer. Best of luck. Frank. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-05-17 86188
You might pressure test the cooling system and run a leak-down compression check. Something I'll call 'block test' can be put into an engine to detect exhaust gases in the coolant. The trouble with figuring the problem of a one way leak is that the oil and coolant systems are separate. There has to be a path between them and the oil pressure always would have to be higher than the coolant pressure. That wouldn't be the case for anything involving cylinders, although would be good to check for white exhaust and also crankcase blowby. I guess there's certainty that no coolant is in the oil.
If it's coming from exhaust gases there should be gas as well as oil in the coolant. If it's coming from the oil supply there's not a lot of opportunity if the oil feed to the rocker arm is through an external tube. It might be good to check the oil and coolant systems to see where there's opportunity for a one way exchange and also the possibility that it's diesel or hydraulic oil. If the oil supply goes through the head there could be a crack between high-pressure oil and coolant. passages.
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