what temp is overheating?

[darrylrobert]

ive got my overheating temp alarm set at 104 C and ive reached it while stuck in traffic on a 30 C day (AC off). It also alarmed at a fast food drive through, couldnt hear the fan working. What should be the abnormally hot temp be or atleast the temp that the fan should be working at?

2001 xc70 cluster digital modification

[pgill]

There are several factors to consider.

1. What mixture of Ethylene Glycol to water are you using (lets assume 50/50)

2. Are you using a pressure relieving radiator cap (lets assume 12 PSI)


50/50 mix without a pressure cap boils at 107 C


50/50 mixture with a 12 psi cap boils at 127 C



For my LR2 (a P3 with a Volvo engine) it will give me a warning at 127 C


I wouldn't worry about numbers below 107 C

https://www.gomog.com/allmorgan/coolantcolors.html


Good luck

Paul

[oragex]

As above, actually the radiator fan will start spinning at 105C . Cruising coolant temp is around 90C, thermostat opens from 90 to 95C full open. Gage needle is still in the middle at 105C. You have a burnt bulb at the message display

[darrylrobert]

i am using a pre mixed product anti freeze anti boil. Arnt all the caps pressure vented? its green in colour.

[oragex]

Yes, at least the genuine ones. You may also want to check the tiny backflow hose near the cap, the clamp must be tight to keep the system pressure

[pgill]

i am using a pre mixed product anti freeze anti boil. Arnt all the caps pressure vented? its green in colour.

They typically are if they aren't broken.

But you would need to test the cap to know for sure that it works.

However a broken cap that won't hold any pressure shouldn't be a problem until the temperature gets above 107 C. (for a 50/50 mix)


To answer you initial question if you phase change the coolant from the liquid phase to the vapor phase then you are by definition overheating.


Hopefully this helps

Paul

[prwood]

Very curious about expected normal temps as well. I produced this graph of ECT vs Speed after a driving session a few days ago. It seems that the average temp when driving was around 195F, but climbed up to 205-210F after idling for a while. The dashboard temperature gauge stayed around the middle from about 185F all the way up to 210F, so I'm assuming the ECU considers all of that to be "normal" range.

[RickHaleParker]

Green cap is 1.5 bars. At 1.5 bars of pressure the boiling point of water is 112 °C ( 233 ° F ).

[darrylrobert]

So the engine cooling fan activated during or after shutdown today,engine ECT was 99C (AC off) so im now thinking the engine cooling fan operation is dependent on a few factors/sensors, most likely the ambient intake temp or even ambient temp (30 C)