after my trip to Stoneleigh, maybe 120 odd miles in total including 70 mph on motroway, I found my radiator fan on more than normal.
Investigation showed that the top head tank (cortina rad) was devoid of water; this is where the fan switch is and this part got hotter than the
radiator core.
Anyway, I since fitted a overflow bottle* to catch and return any water and after a 1/2 drive on Sunday, there was no water at all in there which is
not what I expected.. (I will look inside the radiator as they may give clues).
So what could have caused this? And why is it not happening now? (can't rule out that I may have not fitted the cap tightly before) Was it
motorway driving that was responsible?
It could be head gasket but there isn't any steam or water coming out and spark plugs look right.
* re: over flow bottle - this is locost, ofcourse - using a Tesco liquid soap bottle; several bottles were destroyed i nthe process to find one that
can take boiling water.
This may help (on the other hand, it may not...)
LINK
David
Sticking thermostat could account for that.
Cool running /short distances mean it's not getting really hot so restricted flow doesn't show up and vice versa.
Try taking it out and immersing it in water at the correct temp (use the greenhouse thermometer) to see what's going on.
Alt. replace it anyway.
Cheers, Pewe 
quote:
Originally posted by 02GF74
using a Tesco liquid soap bottle; several bottles were destroyed i nthe process to find one that can take boiling water.
i'm currently using a 3litre robinsons orange juice bottle as my expansion bottle, as it was the first thing that came to hand in the garage when
it first spat all the water out.
it's done a couple of hundred miles with no trouble, it's just a bit bulky. it's cable tied to the battery panel edge.
i might get round to changing it at some point.....
tom