Home » GM 6.5 » GM/Detroit 6.5L – COOLING SYSTEM


All C/K-Model vehicles have pressure-type engine cooling systems with thermostatic control of the coolant circulation. The cooling system is sealed by a pressure-type cap that allows the system to operate at high­ er than atmospheric pressure. The high pressure operation raises the boiling point of the coolant, which increases the cooling efficiency of the radiator. The 105 kPa (15 psi) pressure cap raises the boiling point of the coolant to about 125°C (257T) at sea level.

The radiator cap has an integral pressure-vacuum valve. This valve releases the expanding coolant when it reaches approximately 105 kPa (15 psi) and routes it to the coolant recovery reservoir. The vent function allows the coolant to return to the radiator. As the system cools, the extra coolant in the reservoir is drawn into the radiator through the vent valve. The nominal 105 kPa (15 psi) pressure will not be reached until the system is working at maximum capacity. Any air or vapor in the cooling system will be forced to the coolant reservoir and out through the vent tube at the top of the reservoir. In this manner, the radiator keeps itself full at all times.


Leave a Reply

Your email address will not be published. Required fields are marked *