[DeTomaso] Capacity of overflow tank

[Jack Donahue]

Mike:
You lost me with "a good smooth flat neck on top of the pressure tank".  And what do you mean by a "matching" cap and filler neck? 
KISS?  Keep it simple? stock? simply stock?
Jack
On May 1, 2013, at 1:59 PM, MikeLDrew at aol.com wrote:

> 
> In a message dated 4/30/13 12 14 45, demongusta at me.com writes:
> 
> 
>> Along those same lines, I have the stock set-up. So now it's terminology, I think. I hear people on The List refer to "swirl tanks", "over-flow tanks", and "expansion chambers". Are we talking about the same things?
> 
> >>>Forget 'expansion chamber'; that's the fat part of a two-stroke motorcycle exhaust system.
> 
> The Pantera has two tanks.  One is the pressure tank, also called the swirl tank, while the other is the overflow tank, also called the expansion tank.
> 
>> > Please delineate the differences. Getting confused as to how many tanks we need, or are they all different names for the same tank? 
>> Confused.
>> 
> >>>The pressure tank has a proper 13-16 psi radiator cap on it.  In a normal front-engined car, the radiator has a top and bottom tank, the top tank is higher than the engine, and it has a radiator cap on it.   On our cars, the radiator is lower than the engine, and since the radiator cap has to be at the highest point in the system, they created the pressure tank.  While they probably could have gotten away with a simple pipe with a fitting for a radiator cap, by making it a tank, with water being pumped in the top and sucked out the bottom, the theory is that it deaerates due to the swirl effect.  Whether that's true or not is a subject of debate, and some people here have done away with one or both tanks with no apparent ill effect.
> 
> The overflow tank is just that--it provides a place for water to go when the coolant heats up and expands.   Rather than pushing past the radiator cap and dumping on the ground, when the pressure cap opens up, the fluid is routed from a fitting at the top of the pressure tank, to a fitting at the bottom of the expansion tank, and excess fluid is pumped into the expansion tank.  As the mixture cools down when the car is shut off, as long as the pressure cap is good and you have a good seal, vacuum draws the excess water back into the main cooling system.
> 
> If the pressure cap is bad, it's possible to seal well enough to pump fluid into the expansion tank, but to suck air from outside, instead of water from the expansion tank.  Thus you get repeated cycles of filling the expansion tank and replacing that fluid with air, and air in the system leads to overheating.  That's why it's important to have a good radiator cap AND a good, smooth, flat neck on the top of the pressure tank.   It also illustrates why you have to have matching cap and filler neck, as European necks have a different shape and characteristics and thus demand the use of a European-style radiator cap.  If you throw a Mustang cap on a stock Pantera tank, it won't seal properly (probably).  Meanwhile, most (all?) aftermarket tanks are made with US-style necks and thus require the use of US-style caps.
> 
> I am fond of the KISS principle and still run both tanks in the standard configuration--meaning a zero PSI cap on the overflow/expansion tank, and a 13-16 psi pressure cap on the pressure tank.  Zero overheating problems, even idling in traffic in Phoenix the other day it never got over 210 degrees, and normally runs right at 180 when going down the road.
> 
> Mike