Why is my 800GS squirting coolant fluid UP at me?

[GB]

Ok, so here I am riding around Colorado on my "trusty" 800GS, when I noticed some fluid shooting up from the right side of the cockpit next to the right fork leg and then blown on my helmet covered face due to the wind while riding.

I couldn't figure out where it was coming from, so I checked the expansion tank and rad covers and both are tight.

Last night as I was pulling into the parking lot of where I'm staying and going slowly, when I apply the brakes, I see a stream of rad fluid shooting straight up about 2 feet in the air... This has happened 3 times after some all day riding.

I checked the weeping hole on the bottom of the water pump and it seems dry, no sign of leaks there... any ideas why or where the coolant is coming from?

[Toadride]

Ahh, the old brake lines hooked up to the rad trick.

[AlanI]

You and Tomfoolery76 both - only in this instance it's a F650. Unbelievable, never heard of or seen this problem before and now twice in 2 days and both in Colorado. Somethings not right here. http://f800riders.org/forum/showthread.php?t=48249

[soph9]

I bet your coolant was topped up too much and it is simple leaking from the cap...the cap can loosen with regular riding believe it or not...tighten the cap, check the level of the coolant.....

[GrizGirl]

Mine started doing this a little over a week ago. There is a very small relief valve that the coolant is coming out of (I think it is in the center of the expansion tank lid). Most likely it is caused by the lower boiling point of water at high altitudes and there being water in the coolant. Fixed a little piece of plastic over the top of the expansion tank so I don't get hit by the geyser of coolant. I need to check the coolant to see its mix of water/coolant and will be adding some straight coolant to see if it fixes the problem.

If anybody finds out there is something else going on, I'd love to hear about it but from talking to the mechanic and observing this over the last week I'm pretty convinced it is this simple.

Cathy

[Mknpwr]

They all do that.

But seriously, I can't believe BMW would make something that is so unsafe. It reminds me of the exploding final drives on the 1200GS.

For the record I rode an 1150 GS for several years. Great bike!

[Bicyclist]

The S/STs have been known to piss out the expansion tank cap breather hole. The cure is to lower the level of the coolant in the tank to the min line. Take a look at the level of coolant in the expansion tank.

[soph9]

hmmmmmmmmmm...great idea....

I have noticed on our 2 bikes BMW tends to fill the coolant too much after a service...they did this with my oil too.....

[AlanI]

Originally Posted by GrizGirl

There is a very small relief valve that the coolant is coming out of (I think it is in the center of the expansion tank lid). Most likely it is caused by the lower boiling point of water at high altitudes and there being water in the coolant. Fixed a little piece of plastic over the top of the expansion tank so I don't get hit by the geyser of coolant.

I do believe you've nailed the problem Cathy. I've just checked my 800 and indeed there is a small, very small, hole in the cap. I wasn't aware of that and good to know as I'm off into high altitudes this coming weekend (Italian alps) so now won't be left wondering WTF if this should happen to me.

[Tor]

The air has to go somewhere when the coolant fills up the bottle. If you see any coolant on your bike when you happen to lay it on its side, that would be where it's coming from .

[Moto Mikey]

My bike did the exact same thing last month when I was out on a 4 day ride. Never did find out exactly what the cause was. I think it was coming from the rad cap, which lifted under pressure.

Also this happened at around 7000-8000 ft elevation.

ride report and leak issue:
http://www.advrider.com/forums/showthread.php?t=597322

[CheckerdD]

Since your in Colorado ride the bike down Black Bear into Teluride. That should scare the shit out of you such that you wont even worry about coolant. Dave

[GrizGirl]

I lowered the level to just above the min line at my house, which is about 7000 feet. Went to Colorado on Saturday and all was good until I experienced the problem again at about 10,000 feet or so. And probably again at about 11,000. The pressure and level must finally be where it needs to be for those altitudes because it seems to have stopped now. So even if you adjust the level you may still experience the problem as you climb in altitude.

Just something to keep in mind. Maybe it's a Colorado thing.

[GrizGirl]

Originally Posted by Mikey636

My bike did the exact same thing last month when I was out on a 4 day ride. Never did find out exactly what the cause was. I think it was coming from the rad cap, which lifted under pressure.

Also this happened at around 7000-8000 ft elevation.

ride report and leak issue:
http://www.advrider.com/forums/showthread.php?t=597322

Radiator cap is on the lower left. You said the spray was coming from the right, which means it was coming from your expansion tank relief valve.

Probably just the same issue as everyone else. You climbed in altitude, the coolant/water mixture expanded and relieved out the valve.

It's scary when it first happens and you don't know what it is. When it first did it to me several weeks back it was disconcerting. But now that I know what it is, I just go with it and keep my eye on the level as I go down in altitude in case I need to add some coolant.

Sucks about your flat. An argument for tubeless tires for sure!

Cathy

[AlanI]

Originally Posted by GrizGirl

Radiator cap is on the lower left. You said the spray was coming from the right, which means it was coming from your expansion tank relief valve.

Does anyone (Joel perhaps) understand fully how this coolant system works? Cathy uses the term 'valve' - but this term surely implies some form of off/on mechanism whether it be a manually turned thing as simple as a household tap, or a one way valve such as a mushroom valve which relieves pressure in one direction only and seats itself against returns. The hole in the expansion cap is just that - a hole - with no form of mechanism whatsoever. As the coolant system is pressurised - evident from the radiator cap as opposed to the expansion tank cap - how does the system remain pressurised by the presence of a straight hole to atmosphere in the expansion tank cap. Is there another valve mechanism - a proper valve - somewhere else in the system?