[DeTomaso] TESTED: Re: Pressure Cap

[Barry Seib]

Rich

That is absolutely the best explanation I've seen - for why we shouldn't
have a pressure cap on the hot side of the cooling system.

Thanks
Barry

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I sometimes hate to give advise on cooling systems since there are so many
opinions and different needs in different parts of the country. I am in
Phoenix Arizona.

I tested and measured the increased pressure created by the water pump to
push water through the radiator.  It was something like 4 to 7 lbs.

The reason this is important is because when you fill the swirl tank full
and allow the car to heat up, the expansion of water creates pressure to the
cap rating then pushes through the cap to the expansion tank.

After that happens when you drive the car and rev the engine the water pump
pushes the water harder causing more pressure and you again exceed the cap
pressure and actually start to push water out of the cooling system until
you get back to the cap pressure.

Then you have pushed more water to the expansion tank and the system is no
longer full at the cap pressure.   Then when you go back to idle you will
have the 4 to 7 lbs less pressure and you could start boiling the water
since without the pressure water boils a lower temps.

This is why I think the best system is to create a pressure cap on the
suction side of the water pump and make the swirl cap a fill cap not a
pressure cap.

I hope I do not start another round of controversy.

Rich