Symptoms of an airlock?

[DarnPB]

There are two sensors in the top hose from the head. They are very easy to remove, just a slidy clip and a pull. Remove one and fill the system until water flows from the hose then refit the sensor. These are high in the system so the air should be able to find its way up there.

[rongti]

Have you tried getting a new blue cap for the header tank?  The old ones are faulty and dont work properly which could be causing the water to bubble up out of the header tank.  Also sorry to put a downer on the post, but I had similar symptoms to this and it turned out to be the head gasket.  The plus point being I'm no expert and I changed it in about 4 hours and all fine for past 2000 miles now !

[Conker]

...I changed it in about 4 hours and all fine for past 2000 miles now !

The gasket job all depends on how easy your exhaust manifold comes off, or alternatively whether you can squeeze the head out with the downpipe still attached. I reckon it took me 8 hours.

[rongti]

Thats fair comment.  I managed to remove the downpipe because I got all but one bolt off and then spent about half an hour spashing the crap out of it before it sheared off.  Lot's of WD40 the day before helps!  I only have an 8V, god knows what a 16v would be like :-/ !?

[james_16v]

Thanks for everyones suggestions
After driving the car the last two days its still losing water so I booked the car into the garage and he has told me the head gasket is on its way out! 
He said theres no telling how long it will last and as its my daily its booked in for a replacement ASAP. Could have done without it this side of Christmas and to make it worse he has found my oil leak which is coming from the crankshaft oil seal which is a gearbox off job apparently. Never mind it will all be sorted early next week albeit with me a few hundred quid lighter.
Ill keep you posted 

[Conker]

Be careful with this as a lot of the garages I've used love to say "its the headgasket".

For example, how the f##k does he know its "on the way out"?  Its either failing a compression test/exhaust gas test/or mayo test, or its not. A head gasket is either leaking, or its not. If its not, it doesn't need replacing.

Perhaps he's right, but definitely get the test results first!!!

For example, we've just had a right load of bother with my missus's car where dickhead garage no.1 said it's headgasket had gone, whereas good garage no.2's [second opinion] found a coolant leak in the rad itself, so any water drips we're instantly evaporating making it hard to trace. What a bunch of tossers.

[danny_p]

never had  a any problems with mk2's and airlocks.   ksy pour the water in  nice and steady, try not to let the level go above the small bledd pipe to the expansion tank as it fills better when its below.  start car give it a couple of revs add more water put the cap on and take it for a 5 minute drive,  then top up if needed.

[sharpie]

never had  a any problems with mk2's and airlocks.   ksy pour the water in  nice and steady, try not to let the level go above the small bledd pipe to the expansion tank as it fills better when its below.  start car give it a couple of revs add more water put the cap on and take it for a 5 minute drive,  then top up if needed.

this was well practiced in germany. water was pouring out of the car faster than me and danny could put it in.

[danny_p]

aye that gave us the run around for a while.

the attack of the short ghey littel diamiter changing awkdly placed barsteward pipe. 

[DarnPB]

I'm with Conker on this. I would not be in such a hurry to condem the head gasket without further evidence of the fault. The over boiling occured after you emptied the sysyem and refilled it. My mind would be to start there again.
If the head gasget is the cause of the fault, then you would be getting water where it shouldn't be. ie, the oil, the cylinders etc. If you were getting water in the oil, then more likely than not, you would also get oil in the water which would be visible in your header tank. Water in the cylinders would show up with a compression test and a very clean spark plug, with more than just condesation in the exhaust pipe.