Coolant in Oil?

Is it possible to have coolant in your oil without having coolant coming out of the weep hole in the pump housing. I just purchased my bike used with "12 miles since the last oil change" and the oil seems gray/green to me. I pulled the TDC mark cover off and it had some white foamy stuff on it. No coolant leak on the outside of the motor is evident.

I've also read that this is a common problem with 98s and using a new impeller shaft from a 99 would fix the problem.



Yes, it's entirely possible. In fact, what is not possible is for the oil contamination to be the result of a coolant seal or shaft failure in the water pump. The whole purpose of the weep hole is to provide coolant that goes past the seal a path out of the water pump that doesn't lead to the crankcase, and it works well in that regard.

Your coolant is more likely coming from either the head gasket, or the O-ring seal(s) located at the cylinder base and the joint of the crankcase to the right crankcase cover.

The only case I've seen of a coolant seal contaminating oil was where a rocket scientist decided that he could stop the coolant coming out of the weep hole by "replacing the missing bolt". :banghead:


Okay, so I guess a rebuild of the top end is in order. Thanks for your input and cool diagram.

Here are some pics of the oil that I drained out of my bike. I'm guessing it should be black or even brown, but this is the color that leads me to believe there is coolant in the oil. Both pics are of the same sample of oil. Any thoughts or confirmations? Kind of a crude test, I know, but was hoping this would help diagnose the problem. And yes, pun noted, but not intended.



Surely doesn't look normal.

Put some of the oil in a glass jar and let it stand for a few days. The oil and water should seperate, one being heavier then the other.

If you do have a leak in the head gasket, the bike should blow out a lot of blue or white smoke from the exhaust (although theoretically, you could have a leak between oil and water not affecting the combustion chamber...)

No question. There's coolant/water in that oil.

And there wasn't any smoke coming from the exhaust when I started or ran the bike for the 2 miles that I rode it. I'm thinking you're right grayracer in that it is most likely a leak between the cylinder and the engine case.

In my experience the oil and water will not separate in this case. It is mixed so thoroughly by the moving parts that it becomes an emulsion rather than a mix of two ingredients. And it is REALLY bad for bearing lubrication.

Yeah, can't imagine it would be very good for my engine. I'm hoping the bike will at least run for a little while after I freshen up the top end. Live and learn I guess.

A note to folks buying a used bike. Look at the oil first! Ticks me off that someone would be so dishonest about the condition of a bike, just to make a buck.

12 miles since the last oil change
Consider the possibility that there's nothing wrong with the engine except for the fact that the bike slurped up a load of water when he stalled it in a stream at mile 6.

Hmmm, do I have that kind of luck? Should I just change out the oil see if that does anything? Or should I just check the whole top end because the bike is 12 years old and who knows what's going on in there? Or should I just call him and ask him...?

Would flooding the engine make the oil look like this or is most likely from coolant or water. I did flood it when I first got it because I was new to the starting procedure, but that was only one time.

Here's what it looks like today after sitting for a few days.


Edited by Ebola

I would change the oil and check to make sure the weep hole was not plugged, and go for a short ride to test it. And I would call the seller.

I think your bottom end would probably be ok. I have seen a few bikes with the same problem and it didn't ruin the bottom end.

What caused the problem with the bikes in your experience?

Even though the detergents in the oil are specifically designed to absorb and hold water, the two will separate a little if you leave them sit a while. If you can get them to separate enough to determine whether there's coolant present or just water, it will help you figure things out a bit better, assuming there was coolant in the engine.

Coolant in the oil would mean an engine problem. Water would be from outside. The water/coolant will be on the bottom either way.

Glass container, coming up.

Dude, check the coolant level....if it's extremely low that points to the source of your oil "infection"....if it's at the proper level, I'd query the previous owner on when/how often the coolant needed to be filled and when the last time it was filled.

1+1=2 idea.....

And by "flooding the bike" I believe the idea being described is submerging in a water crossing, not flooding due to too much fuel passing through the carb to the cylinder.....2 totalling different meanings.

I checked the fluid level and it was normal. Probably just topped off when he sold me the bike. That's a good question to ask about the coolant needing filling.

I know about the flooding thing. I was just wondering if the fuel going past the rings and into the bottom end would contaminate the oil.

I know about the flooding thing. I was just wondering if the fuel going past the rings and into the bottom end would contaminate the oil.
Yes it will, but the result looks nothing at all like what you have. Fuel in the oil is almost entirely invisible.

And the oil would smell like gas.

I have seen water contamination come from bad head gaskets or water pump seals (two-strokes). And it looks just like that.

Well, the water pump weep hole is not clogged and not dripping. I talked to the PO last night and he said he never had to add coolant and that the reservoir always stayed at the full level. He did mention that he rode the bike in muddy conditions last time he rode. Given that ad that it is extremely in Houston, it's possible that water could have entered through the air box or breather vents.

Since I don't see smoke, I don't think it's a head gasket. Only thing left is the base gasket. I'm going to flush it with a few oil changes and see where I stand. For reference, the oil should be black, right?

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