Coolant hoses

Hello all
I am having a little problem with my coolant hoses I think . Tonight I removed my fairings to get access to my horn as I'm upgrading it and I noticed something happening again . The hoses are appearing to be sucked in flat a bit like a squashed toothpaste tube . I have noticed this happen twice before and have removed the radiator cap and squeezed the hoses . This has resulted in them returning to there normal state . I then check again in a few weeks and they are squashed again . I have marked the level of coolant in the overflow bottle and squeezed the hoses but there is no movement in the level . I am concerned about this but not overly worried as I have done several long rides lately with no problem and also I have never seen the coolant temperature warning light come on .
I would like to understand what is causing this to happen and try to remedy it so it doesn't happen again . My thoughts are that the hoses are beginning to perish . Its an 06 bike with 30k on the clock so it may be time to replace them . My other thought is a blockage in the system somewhere , so while the pump is sucking the coolant through it has no where to go but the constant sucking is constricting the hoses .
I would love to hear if anyone else has had this problem or has heard of it happening . Ant thoughts and comments on a solution would be of great benefit too
.
I eagerly await any comments .
All the best

[yorkie_chris]

Possibly a faulty radiator cap or a blocked or kinked hose to the expansion tank.

Remove the small tube from the radiator neck and blow through it, you should hear bubbles in the expansion tank.

[embee]

As YC says.

There are 2 valves in the cap, one with a high spring load which pressurises the system when it gets hot, and only allows coolant to vent into the expansion bottle when it reaches around a Bar pressure. This raises the boiling point and prevents cavitation etc.

There's also a small low pressure one way valve in the rad cap which allows the system to suck coolant back in from the expansion bottle when it all cools down to keep it full and prevent what you are seeing.

If the small hose is clear and you can blow through it into the expansion bottle as YC suggests, it's very probably the small valve in the cap at fault for one reason or another.

There was a severe kink in the overflow tube just about 1 inch before it joins the bottle . I removed the tube to re-route it expecting the coolant in the bottle to spill through the hose attatchment , but nothing . I removed the bottle and took it to the kitchen to clean it . I poured out the old coolant through the screw cap and filled it with hot water . NONE came out the attatchment . I looked at it and it was blocked solid . I cleaned it out with a straightened paper clip and the water flowed freely . I then re-routed the overflows pipe from the radcap to the bottle so it has plenty of slack and no kinks .
A blocked overflow bottle and a severly kinked overflow pipe . I hope this solves my crushed pipe problem . Thanks very much for the advice .

Interesting the effect it had on your coolant pipes, keep us posted as to whether it fixes the issue. I can see this thread coming in handy again some day for a reader!