Coolant hose - K Series

[Phil G]

What is the exact function of the small bore hose running from the coolant header tank to the inlet side of the engine block? I believe there is a non-return valve of some kind in the block.

[Phil G]

BTTT

Come on you K-Series experts....!  

[revilla]

It's to bleed off air or gas bubbles from the head. The little valve in the outlet on the side of the head is a "jiggle valve" that closes when there is water pressure behind it (from the water pump) but drops open when there is air behind it. The valves can get clogged with deposits from the coolant leading to airlocks in the head, particularly when trying to fill with coolant. You can see the jiggle valve from the back towards the lower left of this picture. Just a captive ball bearing that blocks the hole when there is a significant coolant flow through it.

http://img.photobucket.com/albums/v465/MGJohn/Rover%20%2045%20%20KG51%20NVL/R45Workinprogresschecks006.jpg

[Phil G]

Thanks revilla,

So it vents air into the header tank?

If this was damaged can it be replaced and if so how easy is this task?

Phil

[revilla]

Yes that's right, vents air into the header tank.

I'm not quite sure what you mean by "damaged or had been pushed into the head" ... are you worried that the little check ball bearing may no longer be in place and may have been pushed out backwards? Have you poked something in there? Are you seeing any flow of water back to the header tank through this pipe?