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I had a John Deere 425 lawn tractor come to me with what appears to be coolant getting into the oil. It belongs to a neighbor of mine that was hoping I would be able to fix it. He uses it primarily as a snow blower in the winter as it has a cab on it as well. What he has told me is that he has noticed the oil on the dipstick looks a little foamy and white. He changed the oil a couple times and it cleared up. But after some use he said it comes back looking like that and the level seems to be a bit higher on the dipstick. To me it sounds like a headgasket issue and I can confirm the oil on the dipstick looks a little milky and foamy. It appears to have a Kawasaki FD620D engine. I currently cant get the full model number from the engine because I have to remove the side panels and to do that I have to unbolt part of the cab which I haven't gotten to yet. Ive done some work on the air cooled Kawasaki engines, but not much on the liquid cooled ones. Is there a certain way to test/check that its a head gasket issue vs a water pump. I don't see any external leaks anywhere on the engine and the engine doesn't seem to smoke or burn any. But is it possible that these water pumps can leak internally into the crankcase too?


Any insight is appreciated, thanks

tkos115 said:

He uses it primarily as a snow blower in the winter

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So not much time to burn off any condensation really in frigid temps?? Could be a head gasket or lack of running it till it gets hot???

Do a couple oil dumps now in hot weather and run the snot out of it at FULL revs.

Coolant probably never changed. Turns acidic over time. Seals start leaking and parts break.

Has the oil level risen significantly after being run for a while? That is the most obvious way to tell.

If they are checking the oil right after it has been run there will be aeration in the oil for a little bit of time. The oil needs to be checked when cold.

Another way to determine if it is water is let it sit for a day and then loosen the drain plug just enough to see a drop or two comes out. Water will be first if there is any, then oil will follow. Specific gravity is a neat process, water sinks below oil.

If this engine has a water-cooled oil cooler, the plate gasket between the block and the adapter could likely be bad

I thought it might just be condensation that built up but he said he changed it several times during the warm weather and ran it but it still came back foamy and the level went up a little bit. I would be surprised if the coolant ever got changed but don't know for sure. What ive done is record the oil level after it sat over night. Then I kept my coolant pressure tester on it over night under pressure and by morning it was back to 0psi and I've noticed the oil level went up a little bit. So im pretty certain coolant is getting into the oil somewhere, but I can't tell where.

tkos115 said:

I thought it might just be condensation that built up but he said he changed it several times during the warm weather and ran it but it still came back foamy and the level went up a little bit. I would be surprised if the coolant ever got changed but don't know for sure. What ive done is record the oil level after it sat over night. Then I kept my coolant pressure tester on it over night under pressure and by morning it was back to 0psi and I've noticed the oil level went up a little bit. So im pretty certain coolant is getting into the oil somewhere, but I can't tell where.

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Don't place too much faith in your coolant pressure tester if is aged. I just discovered all 3 of mine were leaking at the housing assembly threads (Stant brand testers).

If you tested under pressure the level should have risen quite a bit.

My tester is about a year and a half old but it could be leaking. But the level did go up a little bit on the dipstick. Maybe an 1/8in or just under. Ill drain it a little bit tomorrow and see if im getting water. Its been sitting for about 2 days now.