Understood but if there are no traces of leaks then it ain't? 
Let me see If I can explain myself thinking.
When you top it up/fill it you do so with no pressure in the system
.When you put the cap on you are not trapping any pressure
.Now if you put the cap on with it warm/hot, cos you were running it and "burping" it then as it cools it will cause a small vacumn, so you would get a hiss posibbly when you next remove it "cold" not pressure
.If you top up to the correct level you have an air space (lets say X).
Now when you run it up to correct temps because of the air space you have "X" it will allow the system to reach a pressure of (lets say Y).
Making sence sofar?
So at "Y" pressure you lose fluid somewhere, till you get to the lower level that yours sits at.
It will sit at that lower level because now "X" is +1.
Now when the expansion of the coolant occurs due to heat it has more air space to pressure so "Y" is -1.
So the pressure now is slightly less and not enough to overcome a leaking connection somewhere.
How was the Science lesson?
.J
yep thats perfectLet me see If I can explain myself thinking.
When you top it up/fill it you do so with no pressure in the system
When you put the cap on you are not trapping any pressure
Now if you put the cap on with it warm/hot, cos you were running it and "burping" it then as it cools it will cause a small vacumn, so you would get a hiss posibbly when you next remove it "cold" not pressure
If you top up to the correct level you have an air space (lets say X).
Now when you run it up to correct temps because of the air space you have "X" it will allow the system to reach a pressure of (lets say Y).
Making sence sofar?
So at "Y" pressure you lose fluid somewhere, till you get to the lower level that yours sits at.
It will sit at that lower level because now "X" is +1.
Now when the expansion of the coolant occurs due to heat it has more air space to pressure so "Y" is -1.
So the pressure now is slightly less and not enough to overcome a leaking connection somewhere.
How was the Science lesson?
J
but wrong
took the cap off when it was cold, no pressure (good) took the cap off when it was hot, no pressure (bad)
topped it up when it was cold, no pressure. messed with the cap and put it back on when it was still cold, no pressure. started the engine and drove to work, stopped the engine and there was some pressure released when i opened the cap (not as much as I expected, but still some)
reasoning - messing with the cap proved the system is capable of holding pressure, to only leak is from the dodgy cap which i bodged enough to hold a bit of pressure (better)
see.. perfect deductionism
Yes but.... Any signs of leaking? 
Can you get your hand under the bottle and check for coolant from the drain that runs over and to the right?
it just seems to overflow from under the cap, no drain pipe like on the p38?
not that theres any wet(or dried) evidence
I'll be gad when you've sorted this out Kermit as all the talking about leaks keeps making me run to the loo
RangeRoller dt
Well-Sprung Member
I'll be gad when you've sorted this out Kermit as all the talking about leaks keeps making me run to the loo
Try tightening the nuts up , any sign of leakage?
I
It goes to the right and down the tank side edge to underneath.
It does yes and into a tube built into the casing.
It goes to the right and down the tank side edge to underneath.
RangeRoller dt
Well-Sprung Member
No need for a sniff test thenI've got plenty of leakage
OK, so nothing under the tank either
Any wetness around the rad areas,
The egr valves and coolers?
Any oil heat exchangers?
Gearbox oil heat exchanger?
The egr valves and coolers?
Any oil heat exchangers?
Gearbox oil heat exchanger?
Mine is differentView attachment 342800if it's the same unit
Are you the 3.6 or the 4.4?
Note there is a black cap at the bottom as well
