the temp sensor or something like the water pump?

 

Last week it was taking a while to come up to mid point then after about 15 mins it would shoot up and stay at centre. It also went down then came back up.

 

but..

 

on the way to Perth last night coming out of Edinburgh the alarm came on with the temp gauge almost in the red. I slowed right down and let it cool down.

 

Nothing leaking underneath no smoke etc etc.

 

Are you losing coolant? Headertank over flowing or bubbling?

CTS (coolant temp sensor) failure is very common on mkiv Golf derived VAG vehicles. If you have the old black type CTS fitted replace it with a genuine VAG green CTS.

To check the water pump look to see if the small headertank return pipe is flowing when the engine is running. It's often easier if you remove the return pipe & hold it over the open headertank that way you can see if it has flow & you don't lose any coolant.

Still have this fecking over heating issue. Back to the garage today and the mechanic replaced the thermostat who said the old one was stuck half open. But still overheating so as I thought from the start it could be the fecking water pump. Also said it may be a radiator issue but what ever it is a little jobbie just rolled out from under my trouser leg.

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Is there flow from the small headertank return pipe? No flow means your water pump is shot.

Yes there is no flow. This is one thing I thought the guy would have checked first rather than replacing the instrument switch then the temp sensor.

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I had the same symptoms, does you car only over heat when driving? And at idle it's ok? My water pump was spinning on the shaft!

I would recommend getting cam belt changed at the same time and maybe the aux belt

Finally got my car back after being in the fecking garage for over a week. Water pump was destroyed so new pump, cam belt and tensioner (£99 quid ?!) replaced. Also got the mechanic to adjust/re-bolt the SAI. Thankfully the loud hair dryer sound has gone. Car running good but bill is eye watering. 

When was it last changed ?

If you're referring to the tensioner - not sure but assume this was done the last time? The belts were due to be replaced this year so it had to be done at some point.