Coolant in the oil?

Well, the inevitable has happened. Bashing through scrub looking for sheep, and the bottom radiator hose got ripped right through leaving a jagged stub on the water pump. Total coolant loss was instant. Not sure how long the engine ran without me noticing the red light, but a matter of 30 seconds, I'd guess.
Problem is now bubbles in the engine oil are happening, with very slight coolant loss. I think that the water pump mechanical seal has failed, due to dirt and munge in the water pump housing. I was under pressure to get the thing going for work the next day, so just drained the rainwater I'd used to get me out of trouble, fitted a new hose (the old one only just held after cutting the torn end square, and got me to the overnight stop) , topped up with Yamalube coolant and started work.
Thing is, is coolant in the oil likely, or oil in the coolant? It is not normal for the oil to be so frothy.

Next move: improve cooling system guards!

Bikes now done more than 30,000 km and about 1550 engine hours.

Frothy oil suggests water contamination. My guess is a blown head gasket or as you say, a damaged water pump seal. I would check the water pump first or do a leak down test.

Elm wrote:

Frothy oil suggests water contamination. My guess is a blown head gasket or as you say, a damaged water pump seal. I would check the water pump first or do a leak down test.

+1. I'd initially suspect a head gasket in an overheating situation.

-morgan

Thank you for your replies, people.

Regrettably, it was neither the seal or the head gasket, but a worn-out cylinder. Std bore Athena kit is on. Now the intake manifold has been found to be exxpanded, so right there I have a possible solution for the worn barrel. All clamps were tight (they will only tighten so far to prevent noobs from crushing the manifold...), but the throttle body is a sloppy fit. Sigh. Waiting for a manifold...

This bike is trying my patience, and my wallet. Looks like there was no damage from the radiator hose episode, though. Happy about that.

Ok, I think I have arrived at solution to the frothy oil. Unlikely to be a coincidence, but who knows.

Here goes. Feel free to disagree - almost everyone else has. First, there was no contamination according to the champ who fixed my bike. This bloke is an acknowledged guru and someone who has problem solved for me before. Second, with the new cylinder on, I rode home about 30km, doing the roll on, roll off blah blah. Frothy oil.

Today, rode up through the Adelaide hills to Lobethal, about 35 km of up and down hill and tight corners, not babying the bloody bike at all, but stopping short of hammering it. At the Lobethal bakery - what?? - hardly any aeration. Home the same way and there's even less.

Seems like worn cylinder/piston/rings and new, unseated rings caused enough blowby to increase crankcase windage to an unacceptable level. In any case, I'm happy.

Bear in mind that I've spent 1700 hours fiding this bike now, and I know what the oil looks like when I stop the engine. My ancient and loyal TTR250 has never aerated its oil in the window (now about 75,000km and f*&% know how many hours - I guess about 4000 - and still doesn't).

In short, it seems that Elm was right. A cylinder leakdown test (as distinct from a radiator leakdown) might have been the clue.