hey guys, i finally got my TD together and running. still a few kinks to work out. right now i'm having trouble with interstate driving. it runs cool as a cucumber while driving around town in stop and go traffic, but as soon as i get up to speed on the interstate it starts to heat up. it never goes into the red but it gets close. the water pump is new, as is the thermostat. the fan kicks on. everything seems to be normal except the temp while on the interstate. you guys ever dealt with this? any ideas? thanks for any help.
Check the lower rad hose. These can sometimes collapse due to water pump suction during sustained high speed driving. I'm not sure if the older cars had a spring inside to prevent collapse, if they did make sure it's in there. If it's real soft just replace it.
Have you checked your EGT? My A3 Jetta started running hotter on highways when I increased boost but stays normal around town. Dont know if this is relevant but I would check?