Is my Radiator okay

[aneesh84]

I have C5 2.0 HDI 138 2005. The temperature outside is 30 degree C, and after a short drive and at idling the coolant temperature was around 90 degrees. I revved a bit (3500 rpm) and got the temperature to 100 and the cooling fan kicked in and the idling temperature was maintained around 93 degrees after the fan cut off.

The thermostat seems fine since the radiator inlet seems hot after 85 degree

What made me suspicious of my radiator was that the bottom left area felt cool, while the other areas were quite hot, especially the upper part of the radiator. Is the radiator supposed to be uniformly hot all over? Or could this mean portions of the radiator are blocked?

[white exec]

A radiator in good condition will often feel noticeably cooler at the bottom than the top. Hot water from the engine/thermostat enters the radiator at the top, gets cooled, and then (under action of the pump, and because it's denser) falls to the bottom, for re-circulation.

Around 90°C is a healthy normal operating temperature, and up to 100/110 or so when working hard, even though the thermostat is rated at a lower temp.

The 'stat marked temperature is only its designed "opening temperature", and the figure below which it should not allow running temperature to fall, even when driving in extremely cold conditions. The 'stat has no effect on how hot things can get - that is down to the radiator and its fans.

[aneesh84]

Very informative comment. Well then it seems like all is working well!

Since the thermostats were rated 84 degrees i was under the wrong impression that it should be the temperature to be maintained. Really appreciate for clearing this for me.

[aneesh84]

To add, about the radiator, I noticed that the top area is much hotter than the bottom, but also the right side was hotter than the left.

But this can be explained by the fact that the entry location of the hose is not in the centre of the radiation but towards one side, as in the image below:

[white exec]

A good radiator in good condition will allow heat to escape very quickly, so you're right - the hottest point is likely to be where the hot water comes in. If any part of the radiator develops a permanent localised 'cool spot', then it is likely a blockage in its tubes at that point. In practice, difficult to diagnose, as heat tends to travel across the aluminium rather quickly and well. Having said that, do expect the bottom to be not as hot as the top!