Hi,

On a rtw at the moment, F650 GS Dakar. Bike has done 100000km in total. Had a bad breakdown yesterday night near Sucre/Bolivia. Coolant warning light went on, coolant is spilling out of the reservoir...

Background:
Last coolant/oil change was done about 4000km ago in Buenos Aires. I noticed some coolant leaking between waterpump cover and clutch cover, but it was literally just a few drops – maybe 50ml over the course of 2000km. So I ignored it. (I have two fellow round-the-world riders coming down from BMW Colombia who're gonna bring a new waterpump cover seal and new waterpump seals).
I also notice a little build up of dirt/grease around the "coolant hole" near the waterpump. But didn't notice any oil or water leakage apart from the miniscure few drops of water as described above.
For the past 3000km, I've been riding with the water level above "max", so I could check the water level by poking my finger into the reservoir. (Is too much water in the reservoir a problem? Maybe in high altitudes)? anyway....

Today:
Last big ride was from La Paz (4200m) to Sucre (2500m). No problems whatsoever. Then I stayed in Sucre for 3 weeks for a break, where I used the bike only twice for 5km each time.
Today I wanted to go for a 200km ride, but after 30km all at once my water warning light came on. I stopped straight-away and had water spilling out of the overflow water reservoir.

Took off the radiator cap – water in the radiator was good level / no air.
Water in the reservoir looked clean (luke-warm water, but no traces of swimming oil).
Checked the bleeding screw on right-hand-side of engine. Just the tiniest(!) amount of air coming out of there – literally nothing worth mentioning I think.
Checked the oil level – quite a bit less than expected (the bike's never lost any oil in-between oil changes). Still, the oil reservoir was NOT empty, maybe 1/2cm below minimum.
Started up the engine with the radiator-cap off. No bubbles coming up, so (I was told) the water pump should be OK (?)
Put radiator-cap back on and heated the engine up until the fan came on. All good – no warning light.
Topped-up the oil as good as I could (bike being on a slight slope).
Rode another 2-3 km (uphill). Boom.... again, the warning light came on and I was loosing water, which again was coming out of the reservoir. I had the impression that the oil went from "max" to "min". But then again, I was on a downhill slope when I topped it up, and now on an uphill-slope. So I really am not sure. But anyway – even in the worst case, the engine wouldn't eat 100-200ml of oil on 2km, no? (Also, I had someone following me and they didn't notice any smoke from the exhaust they said).

So we waited for a truck who gave me a lift mack into Sucre (not a bad place for mechanics an parts, at least for Bolivian standards).

On both incidents, the water in the reservoir was luke-warm, and it had no sign of oil. And the radiator came on. Still, I have the impression I might be loosing oil. Or it could be a "block" in the coolant system somewhere... I don't know.

I'll consult a mechanic tomorrow – but to be honest: in this country, even a dedicated tire-changing place can potentially **** up a simple tire-change. And I've never seen an F650 here either – that's why I'm hoping for some pointers/ideas from the forum...
Anyone got any ideas or had a similar experience? Headgasket? Water-pump seals? Blockage in the coolant system? Thermostat?

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