Bongo Fury

Before the stat opens, the level in the funnel will drop with revs. During my last change this was what I was expecting and is what happened.

I had a temp sensor dangling in the funnel, and at around 82deg, the level fell less with revs and eventually started rising. In essence, the effect of the right pedal on coolant level was reversed once my stat opened.

Is that supposed to happen?

IMHO, your system sounds as if it is doing exactly as it should.

Liquids will always take the easiest route – ALWAYS.

Before the stat opens, the pump is dragging coolant FROM the head and shoving it via the top hose to the expansion tank, and from there, back to the pump via a very small orifice.
So it’s dragging it OUT of the bleed pipe.

When the stat opens, the flow is no longer through the restricted header tank, but takes the easier route through the radiator, ie: no longer dragging it from the bleed pipe.

Had a rethink on cooling system so may post up my current thoughts in diagram form (if there is any interest).

Thanks, Steve. This reads like what I was seeing is expected behaviour, then - I hope so!

widdowson2008 wrote:Had a rethink on cooling system so may post up my current thoughts in diagram form (if there is any interest).

Most certainly!

thats exactly what should happen matt, i use this to spot problems with flow in rads etc or indeed damaged heads, this only happens when things are near normal.

come on steve you have had a long enough break now get back in the saddle .