Hi Guys

Had copied the following post from one of th treads from this forum. If i am not wrong the end story once you read out this tread tells us that if we have suppose 100 C raditor cap during summers it will open up and release the hot pressure from the raditor on 100 degrees C temprature of the coolant.

If i am wrong pl correct me and guide me as i have 140 degrees coolant reseviour bottle cap. I personally feel if i change it with 100 that might bring the temp down in my car. My car presently run in between 100-105 in rush area. Just wanted to double cross this from you guys if it helps me ....



Pressure(kPa) Boiling point: 'C 'F
47 80 176
68 90 194
100 100 212
140 110 230
195 120 248..."

Be careful! You have to remember that the pressure in the system is going to be that cap pressure (where "100" = 1.00 Atmosphere, or Bar) OVER ambient atmospheric pressure (which is 1.00 Bar at sea level, and a little less up in the mountains"), so that chart might be a little misleading to a lay reader who doesn't know to add ambient pressure to the system's pressure determined by the cap's release rating.
Example, that chart taken literally, using the cap "100" could mean sea level pressure -- same as ambient -- and thus offering no retention of pressure at all at sea level. In fact, the cap "100" allows for one atmosphere of pressure OVER ambient pressure (before releasing), or actually TWO atmospheres of pressure within the cooling system.
In other words, your chart implies that a "100" cap allows water to boil at 100 C or 212 F, whereas, in fact, that "100" cap will permit the coolant to rise to about 120 deg
before boiling, the equivalent of TWO atmospheres.