M.K4 2 litre GTI engine n/a

Feel free to move this if its in the wrong section. I just bought a 2002  V.W sharan as a  camper/ fishing mobile. It has  the ATM engine as fitted to the early GTI . Problem is the rad fan isn't coming on , I hooked it up to the battery and it works ,I bridged the connector at the thermoswitch and it works . I replaced the coolant temp sensor to the cyl head ,I replaced the thermostat, I replaced the thermoswitch in the rad also .The temp gauge is going to 120 then its going back to zero and when i turn ignition off and restart the engine my oil light and alarm is coming on. There is also no hot air coming from the heater even though gauge is going to 120. I've noticed the bottom hose from the block is n't getting hot and the top hose from the rad to the head is hot .Also there is a secondary water pump beside bulk head which is broken ,I have it bypassed with  a pipe joiner ,I believe this cools system after engine is switched off. The car has air con ( SO IT HAS TWO RAD FANS) but the pipe is broken ,so no gas in the system. What else should I Check?,Could my water pump be F***ed? How do I check ? Is this part Of the Timing belt set up ? I've done loads of  belt changes on my G60 engine. But I don't like the tensioner set up on these engines and wouldn't change it myself .So Its kind of  a last resort ,doing the waterpump and i'll probably end up scrapping it as  I only bought this for parts for my diesel Sharan, but its really clean with only 90k on it with a bit of main dealer service history and a 6 speed box  and its  5 years younger than the Sharan I have  .So if anybody has  any suggestions I'd love to hear them .Many thanks Ger

Don't really know any thing about these newer VW engines as I try to avoid working on any engine with lots of sensors and a computer attached to it but going back to old school problems…

Is there an air lock?
If you start the car with the expansion tank cap off is there water flowing?

When the car was lasted serviced with a cam belt change did they fit a new water pump?

Cheers, yes I've tried bleeeding system  afew times dont think thats my problem,Cambelt waterpump done about 20k ago according to prev owner

Back to this the other thorn in my side, I got a sniff test done on this and the head gasket is ok .I originally thought the rads where bust but they do come on. I replaced the thermostat. and the coolant temp sensor  ,Also changed the thermoswitch for another one in my diesel.My thermostat is working as the bottom hose is getting hot when stat is opening also noticed my temp gauge was resetting to zero when the fans kicked in .Above I said oil light and alarm is coming on its actually the temp light. Mark 1 gls mentioned something about water flowing ,from where ?The small hose to expansion tank ? I didnt notice any. Also I took thermostat housing off and spun crank I can feel just about, the  fins on waterpump turning.