F800GS coolant reservoir/header tank

[indylead]

Hi guys, this is probably a stupid question (and I couldn't find anything in here with the search) but hey, I figure better to ask.

I recently had some coolant water puddle under the bike (2011 F800GS) following a ride, maybe half a cup in total. Only thing of note on the ride was that the fan had cut in just before I stopped, and this was the first time it had done so in a few weeks since the last service.

I topped up the header tank but it's tricky to see where the max line is, so *may* have over-filled. Problem then re-occurs again with the fan cutting in.

This weekend, I took the side panels off (an experience in it's own right) and ran the bike for a few minutes to see where/how the leak was.

The only thing of note was that there seems to be a small hole in the centre of the header tank cap. This was the only place losing water, and if the engine revved would give a very tiny fountain. As the water level slowly dropped, so did the leak...

So...it seems this is some sort of back-pressure release valve, isn't something to worry about and I need to not over-fill the level - am I right?

 

[Jonnie Boy]

Shouldn't over pressure like that. Head gasket maybe?? Have a look at the dipstick... is there any white gunk evident?

 

[indylead]

Thanks for the reply - a check on the cold engine shows no sign at all of any mayonaise. Oil looks fairly clean still from the service (2k miles ago).

 

[nig5]

It`s not a good idea to top the tank up to the max mark, you want it about half way between min and max

 

[indylead]

Cheers, nig. I'll check the levels and make sure it;s not overfilled.

It was fine on a ride yesterday....maybe it's another mysterious problem that just goes away.

 

[StumpyFingers]

Remove the header tank cap while the engine is cold, Start the bike and let the engine run,as the engine warms up and the thermostat opens it will expel the Air, if any, in the system. The symptoms you mention could be caused by an airlock in the cooling system.

 

[indylead]

I just realised it might be helpful / polite to put an update on here.

After a couple more puddles when the fan cut in, the header tank level has dropped down to the 'max' mark...and is no longer occurring.

Thanks to everyone for the comments / suggestions.

Now I just need to sort out the immobliser problem!

 

[cbutler]

Following on from this...

On my way to work this morning, the bike got quite hot (riding around London) and the fan kicked to level 2, i.e. louder than the normal fan but not max. It has done this before so no issue with that. However, when it did so, I noticed the coolant reservoir cap (which has, I'm guessing, a pressure release hole at the top) leaking out fluid. Quite a bit, but after checking the level it is still at the max mark. Implying that before it must have been above the mark.

Question: is it normal if the bike gets very hot and there is too much in the coolant tank to expel some through the pressure hole?