Unusual overheating problem 1.8 T Mk4 Golf

[tankboy]

A work colleague of mine, who just so happens to have the same model as me, told me of an unusual fault that occured recently on his golf. His temp gauge shot up to the red whilst driving along a normal 'out of town' road. He immediately pulled over but couldnt see anything wrong with the engine. He is also a mechanic and did all he could to investigate and put it down to a faulty temp switch. The wierd thing is is that around town it wasnt overheating which if the coolant pump or cooling fan was faulty, this is where you would expect it to overheat. When VW investigated, they found his coolant pump to be at fault. When driving at reletively low engine speeds, the pump impeller (which was found to have come loose off its shaft) wasnt slipping on the shaft, however at faster speeds the shaft was going too quick for the impellor to maintain contact hence no coolant was pumping around the engine. He said that VW have modified the coolant pump now for an all metal shaft / impellor. maybe a good idea to check and change when doing cambelt!!!

[Crasher]

This is an old problem dating back to around y2000. The plastic impellers are a joke and VW pumps still have them, only aftermarket pumps have metal impellers. It is often murder trying to get customers to have a new pump. On an A6 1.8T we did last week we spent ages bullying the customer into having a pump which in the end he gave in to. When we removed it, the impeller fell off when touched. Just before Christmas, we had a 1.9 TDI 130 in with a failed pump that had actually collapsed and ohh so nearly destroyed the engine. The belt had been replaced just weeks before and all had to be re-done.

[tankboy]

Crasher,
Thanks for that. I know what i'll also be changing when i do my cam belt shortly.