Overflow bottle tube.

[Phyer Phyter]

Hey every one, I’ve noticed my coolant is a bit low in the overflow bottle. I topped it up about a cup I would say. My question is I noticed the tube going into the bottle through the cap. There is a nipple under the cap, shouldn’t there be a tube connected to it so it can draw coolant back into the system as it cools off?

 

[SMSW]

You said you saw the tube from the radiator. If it was floating free of the nipple, you are correct. It should be connected.

 

[Obo]

edit: this is for the 1300. The 1100 may differ.

There are 2 tubes on the overflow bottle.
The bottom one runs up to the radiator cap. It handles the expansion / contraction of the stuff in the radiator as the spring in the cap moves.
The top one runs down behind the engine. It's there as an overflow & a breather.

 

[TerryS]

The coolant expansion tank does not need to be full. It needs to have some liquid just above the lower line when cold. If you fill it too much when cold, it can overflow when the coolant in the engine heats up and expands.

There should be a hose connected to the bottom of the tank that allows the coolant to be sucked back to the engine as it cools off; that hose somtimes perishes near the radiator and that will prevent coolant from being sucked back. The hose from the cap is simply an overflow.

 

[Bush]

It's a good idea to check that the hose to the rad cap is not clogged with "gunk". Removing the hose at the cap end, cutting off about an inch, if it is deteriorated and blowing through it into the overflow tank will clear any obstruction. Good idea to clean the reservoir once in a while too, with some clean rocks and soapy water, shaken not stirred.

 

[Phyer Phyter]

Thank you for the replies, I didn’t realize there’s a tube at the bottom of the bottle. The top tube is an overflow tube.

 

[Obo]

The coolant expansion tank does not need to be full. It needs to have some liquid just above the lower line when cold. If you fill it too much when cold, it can overflow when the coolant in the engine heats up and expands.

There should be a hose connected to the bottom of the tank that allows the coolant to be sucked back to the engine as it cools off; that hose somtimes perishes near the radiator and that will prevent coolant from being sucked back. The hose from the cap is simply an overflow.

*edit: sorry, this is for the ST1300. Just noticed this is posted in the ST1100 section. 1100's may vary from this.

The service manual says to fill it to the upper line (there's a minimum & a maximum)

Max line is shown by my red pen. Easy to see when the Tupperware is off, but if you're filling it with the Tupperware on you want it just at the "bend" about 3" down from the top.




Better to have too much in the overflow tank (and overflow if the bike gets hot) vs not having enough to suck back into the rad if the rad gets too low for some reason.