I have a 2005 dak 4x4 club cab 4.7 . I have replaced the water pump {steel fins} thermostat, fan clutch, flushed system and replaced fluid, no water in oil {not milky} and no oil in rad, and a new rad cap, but the dam thing still over heats in only a short run, like 20km. does any one have any ideas. I can't see any leaks in rad.

 

After the truck is at full operating temperature, if you turn the HVAC cold/hot **** to full hot, do you actually get full-hot air out of the vents?

If not, you've got air trapped in the coolant passages, preventing the coolant from properly flowing throughout (including the heater core in the HVAC unit behind the dash).

 

yes I get full hot air, I do know about air locks, everything works like it's supposed to heat/air it just over heats all the time, even quicker with the air on.

 

Look the radiator over, anything obstructing the airflow like mud? Maybe check for temp drop across radiator, it could be internally blocked.

 

Perhaps consider a couple more possibilities such as:
- it to be possible that everything else is fine and that the real problem is the dash temperature gauge is faulted.
- the internals of parts of the rad may be fouled, partly or mostly blocked. Things like scale, dirt, old coolant sludge, etc. A chemical cleaning rad flush may help.
- the external parts, fins air passages, of the rad may be fouled, partly or mostly blocked. Things like bug carcasses, dust, grasses and tree fuzz, mud, road debris. An acid soak followed by high pressure air or water spray through the fins may help.

 

thanks for the suggestions. I'm going to get a new rad, have done the rad flush thing. I know rads don't last forever, I have 377 thou km on it, that's what driving 200k a day will do

 

Good plan.