ideal engine tempreture D24 TDI

[jpliddy]

hi
can anyone recommend the ideal temperature these engines run at
with the very hot weather here even my bottom hose is hot now but not as hot as the top hose which is very hot after a 20 mile run tonight . the reservoir tank is warm too but not really hot . in normal cool weather coolant is much cooler seems much cooler in winter months but heater has always been good then i still don't have a working tempreture gauge but am always lifting bonnet car does not use any coolant am i concerned over nothing . i know its critical to have a working temp gauge by what you guys say !
regards jim