Noticed this afternoon when washing my bike (2014 300 Racing) that the long coolant hose from the radiator to the water pump is flattened. Before I take it off and check things out, any idea what could cause this or what I should be looking for?

Thanks

Vacuum as the engine cools is usually what collapses a hose, meaning pressure isn't being released in the system. I'd be suspicious that the little pressure valve GG use on the radiator isn't functional. A clogged rad will produce the same effect, but that seems unlikely...

Probably worth mentioning, if you massively overheated it, the system might be functionally fine, but when cooling a really overheated motor can collapse a hose as it creates so much vacuum just from the temp diff, especially if you were washing it (cooling it off) quickly. Make sure there's coolant in it

Just undid the radiator cap (bolt) and the coolant was at the top. After I undid it the collapsed hose was normal again.

Maybe the previous owner topped it up when it was hot?

By the way, the bike was cold when I washed it.

Do I need to flush the system or shall I just see how it is next week?

The trial yesterday was very muddy with lots of flat out in 3rd and it never seemed to get too hot. Radiator was on a lot but you'd expect that, especially with the front pipe and radiator covered splattered with mud.

I would not think too much of it

 Are you sure it did not get flattened while working on the clutch?

Possibly but why wouldn't it go back to shape until I opened the radiator cap?

I'll see how it is this weekend as I have another trial then.

Hi all.

This still happens and I'd like to get to the bottom of it.

Everything seems fine when riding. Once the bike cools off completely the water hose from the bottom of the radiator to the water pump collapses. If I open the radiator cap bolt the hose returns to normal. The water level is at the top of the radiator and never seems to change.

What would cause this? I'm wondering if there's a blockage in the bottom of the radiator and when the pump is running it's not able to get the flow going and so generates a slight vacuum just between the radiator and water pump?

I know people have said leave it but I'm worried eventually it will cause another problem.

Any suggestions?

Shall I flush the system, refill and see what it's like? Any other ideas?

Thanks.

Anyone?

I think the first answer nailed it.

Ok. I've ordered a new pressure release valve so I'll see if that does the trick.