Coolant leak?

Hi all, took my GTi out for a blast the other night and all of a sudden the temp gauge went up and the red light started flashing. Was almost home so just took it gentle, the gauge kept going down then back up again. No obvious sign of a leak when I got back but it was dark so left it til the morning. When checked the header tank was empty but no sign of any wet underneath. Filled it up, no sign of it running out. Started the car up, still no sign. Left it idling, level stayed stable. Took it for a test drive, still no leak!! Have now run it - carefully - for the last two days and the level is still the same. Anyone have a clue what happened?

The only anomaly was a few minutes before the light came on was that I hit a pothole I couldn't avoid and for a while after that was an intermittent clicking sort of noise, bit like a relay opening or shutting.

Its a 1983 1.8GTi Campaign if that makes any difference - quite a few detail pics of her current condition can be seen at fotopic.net if anyones interested.

was there evidence of wetness round the cap, perjhaps the valve in it has gone so its venting too early and/or allowign the coolant to boil. 1st thing to do if coolant fault is put a new blue cap on as theyre easy and chep to replace

I concur with Rubjonny, I've known it a few times where people have been putting rad weld in to their water, to later realise that the relief valve in the header tank cap was knackered!

I've had the same problem with coolant disappearing mysteriously and noticed there were signs of leakage around the gasket that holds the hose from the side of the block (the right side when facing the engine) through the bulkhead to the heater. The gasket was only a pound but when I refitted it the leak was worse, so I took it apart again - lousy job as difficult to get to the screws - and cleaned off the face of the block as well as the gasket holder and replaced it - but when I drove it it still leaked. Filled it up only to see water leaking from the gasket holder on the side of the block, and I can't figure out why that should be, the bolts were tightened right up and the seal should be complete, but it ain't even when cold - anyone less of a moron know why?

I've had the same problem with coolant disappearing mysteriously and noticed there were signs of leakage around the gasket that holds the hose from the side of the block (the right side when facing the engine) through the bulkhead to the heater. The gasket was only a pound but when I refitted it the leak was worse, so I took it apart again - lousy job as difficult to get to the screws - and cleaned off the face of the block as well as the gasket holder and replaced it - but when I drove it it still leaked. Filled it up only to see water leaking from the gasket holder on the side of the block, and I can't figure out why that should be, the bolts were tightened right up and the seal should be complete, but it ain't even when cold - anyone less of a moron know why?