Please Help My Overheating 16v

[hectorite]

I have a Golf gti 16v with an overheating problem. On the motorway the temp sits half way which is fine, but when Im crawling along the car overheats and the temp gauge goes way over and eventually starts jumping around (as if there is fuel starvation).
This is not just in hot weather it was like this in winter and I know the fan works.

This is what people have suggested.

1). The thermostat. The one I have is 87c. Is this correct?

2). The fan. When does it cut in and what type should I have. The one Ive got seems to be single speed with only two prongs. Should it be twin speed with a three prong end?

3). Or somthing else? ie waterpump

Please could someone shed some light on this problem as I dont know what to do.  

[richandhazel]

Hmmm, tricky. Could be the vanes on the water pump have degraded or the thermostat isn't opening fully........something effecting the circulation.
You're sure the electric fan is coming on as that is the obvious culprit.
Here's a little info on the connections that I posted the other day:-

http://homepage.ntlworld.com/richandhazel1/Coolfan.jpg

[pipworks]

Have you tried flushing the radiator out? If you're sure the fan is working and the thermostat is opening at the right time, it's probably a water flow problem.

I drove my er.....(ford) for ages with the thermostat out as it overheated a lot, just meant it took a lot longer to warm up in the mornings!

[golfvr6]

I would change the thermostat and flush out the cooling system. If the problem is still there check the radiator fins for damage, remove the water pump and check the propeller, and finally change the expansion tank pressure cap. Does sound like a strange one cos i your thread made me think of the fan straight away.

[modulater]

When the engine is warm but running normally remove the rad cap and look in the expansion tank, you want to see continous water running from the return pipe. If you see bubbles of air coming into the tank and it looks like a saucepan on simmer then it points to a head gasket.

A friend at work had a similar sounding problem on his BMW which would only boil up in very heavy traffic and was fine driving on the road and it was a slight head gasket leak.

[hectorite]

Cheers for the help guys. Hopefully will be able to sort it out.