Re: 2262-9 288 motor distribution tube

Posted by BH On 2010/9/16 8:44:38

OTG -

Perhaps I can shed a little light.

The cooling system under discussion is pressurized, and the radiator cap uses a pressure relief valve to build up pressure in the system, to a certain point. The pressure raises the boiling point of the engine coolant. I had to look it up, but it's 3 degrees (Fahrenheit) for each additional pound of pressure.

The 15 degree difference between the normal boiling point of water, 212F, and the STB specification, 227F, suggests that a 5-lb. cap was used. However, the 48-54 parts book offers only a 7-lb. cap to service 48-50 models. With a 7-lb. cap, the boiling point of water in a '50 would be raised by 21 degrees, from 212F to 233F.

Yet, there is another aspect to consider.

An added benefit of using antifreeze is that it not only lowers the freezing point of the coolant mixture, but also raises the boiling point. A 50/50 mix of water and ethylene glycol boils at 223F. In that case, with a 7-lb. cap, you would then have an effective boiling point of 244F.

However, you can't simply go to a higher pressure radiator cap to compensate for a overly hot condition. The rest of the cooling system must be designed and built to withstand the additional pressure.