my 1999 c 250 td overheats only when driving, have had it idling for ages and temp sits on 85 c , changed thermostat, flushed rad , all pipes gets hot so i dont think its the waterpump, no oil in water or smoke or noise, as soon as i take her out and up to 60mph the needle shoots up to 120 and power gets governd to 20 mph! any help please.

 

Check this:
1. Insufficient coolant in system,
2. Themostat faulty - not opening,
3. Radiator core blocked, or grille restricted,
4. Cooling fan or viscous coupling faulty,
5. Inaccurate temperature gauge sender unit,
6. Airlock in cooling system and
7. Pressure cap faulty.

 

thanks platonmind

i have the hayens manuel and checked all those, it just seems odd that it doesnt overheat even on high idle but as soon as i go up the road for 2 minutes it goes to red. do you know off a way to check if the pump is working? done a "carrot test" on fan and it seems to be ok.

 

it could be a faulty wire on the sender and its reading more than what it is wont be water pump when they go water every where and if realy bad makes wening noise