Coolant Flow

[msb]

Returned from a ride today and fan came on as I entered my driveway....thought it unusual at that point so I checked the coolant level . Level was well over the High line in the reservoir,  and the level in the rad was low. Obviously not moving through the  system as it should.  New waterpump, T-hose, and coolant tube o-rings and of course coolant 3 years ago, no obvious signs of coolant leaks or issues since. Everything seemed normal when fluids were checked prior to a multi-day ride 2 weeks ago. Any thoughts or suggestions where to look first? Thx.

[John Schmidt]

Radiator cap. Check first to see if the overflow tube might have become pinched.

[RonW]

Unless the coolant warning light lit up I would shrug it off as an anomoly for now. When you drove into your garage you reduced your speed. Perhaps, the coolant was just a fraction under the temperature that would have triggered the fan. The lower air speed allowed the radiator's temperature to go higher. Happens to me on my other bike.

[Jess from VA]

After every ride, I pull up my drive to my double 8' gates and get off, leaving the bike at idle.

I open one door, walk back to the bike shed (50 feet?) and open the doors, walk back to the bike, and the fan has come on.  Takes about one minute.

I usually go the whole day without the fan coming on, unless I get stopped at long lights (or traffic).  If my fan is on more than a minute or so, I shut the bike off and wait till I can roll again.

But the fan comes on nearly every time putting the bike away.  Outside temps seem irrelevant.

The ride home goes from 40mph (few miles) to 25 (about a mile) through the neighborhood.

[Jims99]

I would change the cap if original. If you waited till it was cool before opening the radiator, it should have pulled fluid back into it and shouldn’t be low. If so the cap could be going bad.

[RonW]

Just theory, but I think the radiator purges more volume of coolant than it draws coolant back from the reservoir into the radiator when the engine cools down. For example, during a ride, the radiator dumps 8oz of coolant into the coolant reservoir. When you park the bike, the coolant cools and the resultant vacuum draws 7.9oz of coolant back into the radiator not the full 8oz. Eventually, the coolant level in the radiator ends up lower and lower until it's noticiable and you refill it.

[rws]

OP

The next time you come home with the fan running before assuming a coolant system problem let the bike cool down to ambient temperature (or better yet wait overnight) giving the system a chance to stabilize before checking reservoir level and opening the radiator cap.

[msb]

OP

The next time you come home with the fan running before assuming a coolant system problem let the bike cool down to ambient temperature (or better yet wait overnight) giving the system a chance to stabilize before checking reservoir level and opening the radiator cap.

Thx, appreciate your comment but I've had the bike for going on 21 years so I'm pretty familiar with it...like when the fan comes on and under what conditions and it has also been ridden regularly all year. I also check all my fluid levels regularly regardless of whether there's an issue or not.  This particular circumstance was decidedly out of the norm, which is why I checked. Now after 24 hours the levels in the reservoir and rad haven't stabilized. The system was due to be flushed this Winter ...I'll just do it now , check all the hoses, and replace the rad cap with a new spare I keep. I just wanted to check to see if others  knew of anything else I should be looking at. 

[longrider]

Good idea on the rad cap.   If you are flushing maybe a good time to change out the thermostat.   Without a temp gauge it is more difficult to know if everything is working properly.    If you have an IR temp gun or could borrow one you could have a better idea on whats happening.  Remove the RS pod,  Start it up and gun the RS rad tank near the inlet.  The temp should slowly rise to 185 or so then hold till the rad starts to warm  up as there is no air flow.  At about 212 the fan should cut in. 

Just throwing it out there.

Warren

[rws]

Thx, appreciate your comment but I've had the bike for going on 21 years so I'm pretty familiar with it...like when the fan comes on and under what conditions and it has also been ridden regularly all year. I also check all my fluid levels regularly regardless of whether there's an issue or not.  This particular circumstance was decidedly out of the norm, which is why I checked. Now after 24 hours the levels in the reservoir and rad haven't stabilized. The system was due to be flushed this Winter ...I'll just do it now , check all the hoses, and replace the rad cap with a new spare I keep. I just wanted to check to see if others  knew of anything else I should be looking at.  

How do you think the system will stabilize to normal levels in the overflow tank and rad now when you opened the radiator before it cooled to ambient temp? The system has to stay sealed in order for the rad to suck coolant back from overflow tank as it cools.  You opened it so naturally you witnessed a high level in tank....it hadn't been sucked back to rad yet.  For everything to work properly the system has to be sealed in order for coolant to expand to overflow tank as coolant temps rise and to flow (be sucked) back to rad as it cools.