Re: [Chrysler300] radiator caps

["PaddyCaddy ." <paddycaddy@xxxx>]

Alas, it seems we have another wee disagreement among friends...

If I am not mistaken, higher pressure also impedes the flow volume of 
coolant. If your car was filled with nothing but tap water like in the old 
days, boiling would indeed be the primary fear. But with modern coolant 
mixtures, it is not.

Getting the maximum amount of coolant into and out of the engine is what 
you're really after when idling in 100 degree heat with the AC blasting. 
This is exactly why your car has an idle speed up system for when 
temperatures approach dangerous levels.

Pressure (which remains fairly constant) is not what gets your engine 
temperature back down to safe levels. This is accomplished by increased 
rpms in the water pump churning a greater volume of coolant through the 
system.

My opinion is that changing - say - a 12 pound cap to a 9 pound cap 
increases flow. I got this advice from an old timer who runs an auto repair 
shop called - aptly enough - "John's Radiator." He had recharged my 
Cadillac with Freon and built me a new radiator. WHen I started having 
frequent heat problems, he gave me the lower pressure cap.

While my 276 Hemi that was recently rebuilt for the 300 is problem free in 
the overheating category (no carbon blocking coolant passages, new water 
pump, no AC on the car), my 200,000 mile plus 472 V8 Caddy has benefitted 
from me lowering the pressure on the cap. I've also heard this "trick" from 
others in the industry.

Having a "puke tank" is a must for this to work of course, as it will be 
utilized more with a lower pressure cap. But that is what it is for, after 
all.. It keeps the lower pressure fairly constant and maintains the better 
flow - then takes the overflow coolant back into the system as the 
temperature cools.

Sean.





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