Thirsty Expansion Coolant Vessel

[CDES]

Hoping this isn't too big of an issue.

10 minutes into motorway journey today, I noticed the temperature gauge rising, so about half way between the middle and max line, I pulled over to check the coolant, and it is gone... So along comes motorway incident guy and fills it up, and we watched it drink the contents, TWICE, filled it up a third and let it run and it seemed to settle. I set off to work again, 35 miles down the motorway, got to work and the expansion vessel was empty again... First thought was the head gasket was away, checked the oil filler and it was all nice brown oil.

Anyone experienced anything similar? If so, what was the cause and solution? I'm hoping it is just a leak somewhere... That being said, the amount of leakage under the car is minimal and I put that down to my piss poor aim...

Help.

 

[bashracing]

top it up again,
set the heater to hottest setting,
open the bleed nipple on the thermostat housing until coolant flows, (in the picture)
close bleed screw again,
run it for 10 minutes,
leave to cool down for half an hour,
bleed again

 

[CDES]

Thanks for the reply, I'll give that a go and report back.

 

[CDES]

Turned out to be the radiator leaking. Radweld didn't sort it, so new radiator time tomorrow.