Hi all,

Any idea what could happen?

I was driving my Octy 1.9TDI '99 at around 80mph when I noticed the temperature gauge went up over the normal temp which is in the middle of the gauge scale and reached almost the red area so I stoped and turned the engine off. Unfortunately, I didn't check the hoses coming out from the thermostat as that time I didn't know where they are What I could see straight away was increased coolant level about 1.5inch or a bit more above max level.

I also checked the heatsink (or radiator, whichever is better word) and it was cold.

After around 20mins, when the temperature came back to the normal one I started to drive without any problems and I'm driving since now.

I also noticed then even if the temperature is in the middle of the scale and thermostat works fine it is cold as well.:confused: Whereas the pipe coming into the heatsink is very warm.

Would it be possible that heatsink is efficient enough to cope with cooling?

When when fans should be switched on? I've never seen them running.

One thing more not sure if it maters. Before it happened I was driving with a bit higher revs, not too long about 3mins, I just wanted to check acceleration at 3rd and 4th gear.

What I suspect is that thermostat got stuck. Could it be water pump instead?

Thanks,

Rob

It would be prudent to suspect the water pump and at least get the problem checked by a dealer/garage asap. If it is the pump rather than the thermostat, and you allow the engine to overheat significantly again, the cylinder head gasket could fail resulting in a potentially very expensive repair. Has your car's cambelt been changed recently because, if not, it would be sensible to get it and its tensioner changed at the same time as the pump.

As far as I know from the service schedule book, the cambelt has been changed around 6k miles ago so I wouldn't be worry about that.

How the water pump failure can be identified by a dealer/garage? Connecting to the computer? Is it possible the water pump gets stuck from time to time?

The plastic water pump impeller (vanes) becomes disconnected from the shaft and ceases to pump water around the cooling system. This is a known fault which has been fixed by modifying the water pump which now has a metal impeller.

But how can a dealer/garage detect the failure?

Not sure how water flow works but I could imagine that there is a constant flow around the engine and when the coolant reaches specific temp, the thermostat gets opened to allow coolant flow to the heatsink. Am I right?