I have a 2001 s60 2.4t and I can figure out why its overheating intercooler and radiator were replaced within the last year, replaced the reservoir, replaced reservoir cap twice, replaced thermostat twice, replaced temperature sensor, water pump is working and not leaking or making any noise, radiator fan is kicking on like normal, flushed and put brand new coolant in twice, and no coolant leaks of any. Only thing I can think of at this point is cracked block or a blown head gaskets if anybody has any ideas feel free to let me know.

 

How do you know it's over heating? Gauge? Boil over with visible coolant? Loosing coolant without a puddle? How's the oil look, milky? Have you done a coolant pressure test?

 

The gage pings red and coolant boils and sprays out of the cap and the oil looks good

 

there are a few ways to test. First does the heat come on full blast? How long does it take to overheat (google for ways to test if the water pump has failed internally). If you suspect a headgasket issue, you can measure the cooling system pressure - should be something like 1.2 bar or below - plus if you are getting combustion gasses into the coolant, there's HC test kits ~$40 at Autozone etc.

At this point I would not assume that the water pump is working properly. I think its reasonable to test for a failed head gasket issue via a coolant HC test and possibly a leak down test. Also test for the cooling system pressure to see how quickly the pressure goes up and what it maxes out at...