Boiling temp of water with 7lb radiator cap.

[graham_fuller]

Hi all,
The question is as above. I was stuck in a major traffic jam today in 35 degree heat water temp gauge was reading around 80 degrease or a little more, the temp light didn't come on. So should I assume it didn't boil?
Cheers,
Graham

[graham_fuller]

What I should have said was the boiling point of coolant at 7lbs pressure?
Cheers,
Graham

[Harv]

Graham,

Probably didn't boil. Check water level anyway to be certain.

atmospheric pressure water boils at 100ºC at sea level.
a 7psi cap boils at about 110ºC.
a 9psi cap boils at about 113ºC.
a 12psi cap boils at about 118ºC.

Adding coolant chemicals like glycol can change this a little, as can operating at other than sea level.

Cheers,
Harv

[Harv]

Got me curious... even at the top of Mount Kosciuszko, a 7psi cap would still boil at about 105ºC.

Cheers,
Harv

[Geoff_K]

Graham,
If you are stationary, the outside temp is 35º, and your temp guage is holding 80º, you have a damned good cooling system.
Most standard motors/radiators, under these circumstances (assuming at idle/no load) would over time tend to creep up to 100/105º, and only if you are loosing water (leaks in water pump, cap, cracked head, cores, hoses etc) will temp run up enough to flick on the temp light and give you grief.
If you are towing a van, or climbing a mountain, things could be worse!
Cheers Geoff_K