1990 K100 16v oil in coolant/coolant in oil

[drut]

Checked my oil today & surprised to find level slightly down + mayonnaise in filler cap.Checked overflow bottle and found oil sludge so drained coolant and oil.Found some water in oil and some oil in water but not huge amounts.Rode over 100ml yesterday and bike faultless so rather surprised to say the least. As bike was running fine I suspected oil/water pump but no leak
from weep hole which i poked to make sure was clear,does this mean the head gasket is the cause?
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[daveson]

Are there bubbles in the expansion tank at idle or revs after returning from a ride? After a ride ( or before)  any bubbles? After a ride and turning it off you might see or hear some bubbles even after a minute or so. Oil in the coolant is a horrible thing to find, but could be a simple fix ( or horrible) any water coming out the muffler when you turn the key at cold or warm? Or more than just normal condensation.

[Laitch]

As bike was running fine I suspected oil/water pump but no leak from weep hole which i poked to make sure was clear,does this mean the head gasket is the cause?

The source of the problem still could be the pump seals, drut, according to this comment within a thread describing the same condition as yours.

[drut]

Many thanks for the replies,no bubbles in expansion tank and no change in bikes running.My thoughts are either pump,despite nothing from weep hole,or leak between oil and water passages at head gasket but do not know how find whitch is the cause.Bike has done 41000ml,just fitted new YSS rear shock and really enjoying rides and weather tkhen this.Any suggestions how and what to check or what to pull to bits first would be most welcome.

[frankenduck]

The tach may have been showing your cold cranking amps.

[drut]

"The source of the problem still could be the pump seals, drut, according to this comment within a thread describing the same condition as yours."
Thank you Laitch for that link,reading that I think it worth pulling pump to bits first.

[daveson]

There's still some checks about the gasket.

It's probably the pump, hopefully, it's easy to get to. The leak could be internal or external, leaking out the weep hole. It could be temporary or permanent. Hopefully it's a temporary internal leak. Is that a ridiculous case of wishful thinking, yep. Here's another one, maybe just a loose head bolt.

If you haven't checked the shims for a long time, maybe check them and while you're at it check the head bolts.

After the virus and the lock downs, I didn't ride my brick for a few months. After being parked for a few months there was some coolant on the concrete floor below the weep hole. After a few rides the leak disappeared. Which makes me wonder if you're brick was parked before this leak started. You changed the oil and coolant, maybe keep an eye on it to see if the problem returns, good luck with it anyway.

[Laitch]

The tach may have been showing your cold cranking amps.

[drut]

Update: Removed pump & as suggested found weep hole totally blocked in pump casting.No way it could have been cleared without removing pump & had to be drilled.Stripped pump & found new shaft will be needed but glad to find cause.Many thanks especially to Laitch,this forum is great.Now going to read up on fitting seals.
Regards: Duncan

[Laitch]

This article and this comment go together nicely, but new parts are hard to beat. 

[drut]

Thanks for that,going to go for new shaft as I am trying for certainty.I have mixed feelings about repairing pump given others failures fitting seals but other options are new pump@ 600GBP or 180GBP used pump with 6mth guarantee:both from Motorworks bmw.I would struggle to afford 600GBP for new and think buying a used pump a hell of a gamble.Fortunately I am still in love with the bike despite its weight and my advancing years.

[Past-my-Prime]

Heck, if I can redo the water / oil pump seals, as a definite mechanic / hack, anyone can!

[drut]

Bike back together & test ridden OK.Good to be back on it again!

[Laitch]

Thanks for the update, drut.