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[Entwood]

Expansion tank is prone to minute cracks around the neck where the cap screws on, these can prevent the cap sealing so that it leaks vapour when under pressure, it rarely leaks liquid as there is an "air gap" betwen the surface of the liquid and the cap. However, the loss of pressure reduces the boiling point of the coolant and leads to an increased evaporation of liquid. This could be the reason for your fluid loss.

One way of checking is to run the engine until well hot, ie, the pressure is at its potential maximum, and then to brush a soap solution around the lower edge of the cap, if it is leaking you will get bubbles.

A new expansion tank and cap is less the £50.00 ....

[tunnie]

Thanks 

Was that £50 from Vauxhall recently? Will call dealer today, but I can’t get trade anymore.

I think the dark bits at top, is evaporating coolant, leaving dye behind.

[henryd]

Starting to think again it's expansion tank, I checked tonight, found moisture around the rim of the cap at the bottom.

Top of the tank is showing signs of the dye.... (before this tank was clear all over, with nice red GM coolant) the dye has affected the colour.

Again, bubbling sounds around cap, if my ear is close.

Post up another pic without the cap on showing the neck of the tank,as Entwood says cracks are common there

[dave the builder]

Expansion tank is prone to minute cracks around the neck where the cap screws on, these can prevent the cap sealing so that it leaks vapour when under pressure, it rarely leaks liquid as there is an "air gap" betwen the surface of the liquid and the cap. However, the loss of pressure reduces the boiling point of the coolant and leads to an increased evaporation of liquid. This could be the reason for your fluid loss.

One way of checking is to run the engine until well hot, ie, the pressure is at its potential maximum, and then to brush a soap solution around the lower edge of the cap, if it is leaking you will get bubbles.

A new expansion tank and cap is less the £50.00 ....

I advised he put a  washing up/water solution in an old pump spray bottle a while ago and check for gas leaking round the tank and hoses.
did you not try that Mr Tunnie 

[tunnie]

Starting to think again it's expansion tank, I checked tonight, found moisture around the rim of the cap at the bottom.

Top of the tank is showing signs of the dye.... (before this tank was clear all over, with nice red GM coolant) the dye has affected the colour.

Again, bubbling sounds around cap, if my ear is close.

Post up another pic without the cap on showing the neck of the tank,as Entwood says cracks are common there

Will do, I have inspected it, I could not see any cracks. There were 'whiff's of coolant before new cap.

Expansion tank is prone to minute cracks around the neck where the cap screws on, these can prevent the cap sealing so that it leaks vapour when under pressure, it rarely leaks liquid as there is an "air gap" betwen the surface of the liquid and the cap. However, the loss of pressure reduces the boiling point of the coolant and leads to an increased evaporation of liquid. This could be the reason for your fluid loss.

One way of checking is to run the engine until well hot, ie, the pressure is at its potential maximum, and then to brush a soap solution around the lower edge of the cap, if it is leaking you will get bubbles.

A new expansion tank and cap is less the £50.00 ....

I advised he put a  washing up/water solution in an old pump spray bottle a while ago and check for gas leaking round the tank and hoses.
did you not try that Mr Tunnie 

I did do this, but I did it with engine off, think I need to do it with engine running after it's done a run to/from work. Again it could be so slight that it does not appear. As even over course of an hour, it will drop less than a fingers width in the tank.

[tunnie]

Tank, £71.40 from my local, without a cap, but with a sensor.

Ordered it just to save time, 2 working days so should have it early next week.

[TheBoy]

Ah, I think I had a spare (used but good) tank in my garage.

£71 , I paid sub £30 last one I bought probably 3 years ago

[aaronjb]

Ah, I think I had a spare (used but good) tank in my garage.

Which incarnation of Flammable Garages Ltd, though?

[tunnie]

Ah, I think I had a spare (used but good) tank in my garage.

£71 , I paid sub £30 last one I bought probably 3 years ago

Snap. I put a brand new one in 2.2 to tidy up look of engine bay. That was ~7 years ago though!

Had a spare or have a spare? 

[TheBoy]

Pretty certain I have the one off TBE, that I only swapped with the one from the Silver Bullet because that one was newer/cleaner.

But I could have already given it away, and until I get back home, can't confirm.

[TheBoy]

Ah, I think I had a spare (used but good) tank in my garage.

Which incarnation of Flammable Garages Ltd, though?

Defo this side of "the incident"

[STEMO]

Ah, I think I had a spare (used but good) tank in my garage.

Which incarnation of Flammable Garages Ltd, though?

I wouldn't.....you may invite comments about kamikaze tiles and shattered basins. 

[aaronjb]

Ah, I think I had a spare (used but good) tank in my garage.

Which incarnation of Flammable Garages Ltd, though?

I wouldn't.....you may invite comments about kamikaze tiles and shattered basins. 

At least I still have my post count .. well, this post count. I'm sure I was up to ~10k before it got "reset" last time

[JamesV6CDX]

Are we going to have the first confirmed case of hgf on a 3.2 ?

It wouldn’t be the first. Ask Rae turbo! His was so badly gone, that on turning over the engine, coolant came out of the spark plug holes 

[tunnie]

Are we going to have the first confirmed case of hgf on a 3.2 ?

It wouldn’t be the first. Ask Rae turbo! His was so badly gone, that on turning over the engine, coolant came out of the spark plug holes