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That is a great link you found!!!!!
I have always suspected this, but the magnitude he suggests is more than I ever expected. But I guess with a high rpm, HD water pump and partially blocked radiator it is possible!!!!
More interesting comments he made:
I have always suspected this, but the magnitude he suggests is more than I ever expected. But I guess with a high rpm, HD water pump and partially blocked radiator it is possible!!!!
The HO radiators have the cap on the outlet side! The Renix Bottle cap is on the pump outlet side!!!!!!! So high RPM, HD pump, partial blocked tubes in the radiator would be too much for the 16 lb bottle cap once the bottle runs out of air!!!!
- Crossflow radiators with a fill cap always have the cap on the outlet side. Upright radiators have the cap in the inlet side and thus subject the filler cap to the pressure drop of the radiator's core in addition to the system pressure. This can lower the effective pressure of a 22 PSI cap to as low as 10 PSI.
- Thermostat housing restrictors were useful when upright radiators were used with 7 lb. caps. The restrictor slowed the flow and kept the pressure in the radiator down. This prevented the cap from expelling water and causing the car to overheat. Most people wrongly assumed the car ran hot and expelled water. The cars actually expelled water and ran hot.
More interesting comments he made:
His last comment is poorly worded. He is trying to say that the pressure drop across the core, and the suction/pressure sides of the pump, create a low pressure and high pressure side to the coolant system, that in extreme cases can reach 2 psi on the pump suction side and 20 psi on the pump outlet side (which is the Upper Rad hose side). By extreme, I would think it would take a HP water pump, a nearly blocked radiator (or very undersized relative to the pump), and very high engine rpms.
- The system achieves this pressure only when the system is filled cold. When a warm system is opened and resealed this pressure is not obtainable because the coolant and trapped air are already expanded when the system is sealed.
- A Schrader valve installed in the system will allow the system to be charged by an air hose. This allows an already warm system to achieve operating pressure and minimizes the effect of trapped air in a cold system.
- The fill cap must be the highest point of the system. Surge tanks must be used if the top of the radiator is not the highest point.
- Trapped air seeks the highest point. A new system always has trapped air.
Always fill the surge tank completely, when the system reaches operating temperature it will expel any excess water out the overflow.- Placing a fill cap in the top radiator hose subjects the cap to the pressure drop of the top hose and the radiator core in addition to the system pressure. This can lower the effective pressure of a 22 PSI cap to as low as 2 PSI.
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