Re: [Chrysler300] radiator caps

[Mike Apfelbeck <moparmike@xxxx>]

Higher pressures will not affect the amount of flow in a closed cooling 
system, water does not compress under more pressure, it flows the same. 
However,hot water/coolant mix will be less likely to boil as it is pulled 
into the water pump if it is under pressure. Also, any air bubbles in the 
system would be smaller under more pressure and less likely to affect things.
Straight water has been proven to transmit heat better than a coolant 
mixture, but the realities of needing corrosion resistance, waterpump 
lubrication and todays higher operating temperatures make it impractical.
The only reason I ever put a lower rated pressure cap on was to get by with 
an older radiator, that was getting weak, until I could afford a replacement.

At 12:06 AM 9/3/2002 -0400, PaddyCaddy . wrote:

> 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.