It looks like your fans need some work. Your fan clutch (for the main fan) is apparently shot and needs to be replaced. The fan should have fairly good resistance to rotation with the engine off. On my car the aux. fans seem to always spin at the same speed and they come on when the temp is approx. 90C. Other than that it could be your radiator, thermostat or water pump, but I'd start with the fans.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL