[DeTomaso] TESTED: Re: Pressure Cap

hoppe1 at cox.net hoppe1 at cox.net
Wed Aug 19 11:37:40 EDT 2009


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

 



 Dear Mr. Science,
> 
> 
>                   Very impressive laboratory work in your spare time after dinner!    Well done.
> 
> 
>                                     Warmest regards,  Chuck Engles
> 
> 
> ----- Original Message ----- 
> From: "Asa Jay Laughton" <asajay at asajay.com>
> To: "Pantera REALBIG forum" <detomaso at realbig.com>
> Sent: Tuesday, August 18, 2009 9:35 PM
> Subject: [DeTomaso] TESTED: Re: Pressure Cap
> 
> 
> > Well, you can call me dumb, just don't call me stupid.
> > 
> > I finally did what I should have done months ago.  I tested the swirl 
> > tank with the radiator cap.  I have a Motocraft 13 lb cap that has 
> > worked for years on the Mach I.   This same cap has been on my Pantera 
> > for a long time... and I've always had a boiling over problem.
> > 
> > I removed the swirl tank some time ago in preparation for a cooling 
> > system re-design.  As I'm running short on time and will have all winter 
> > to sort things like that out, I decided to see about putting the stock 
> > system back together, with the new stainless pipes, new hoses, etc.  
> > I'll need a new overflow tank for those that remember the gaping holes, 
> > but the swirl tank appears to be intact.
> > 
> > I rigged up a cooling system pressure tester to it this evening.  I 
> > installed the 13 lb cap and got copious amounts of leakage at less than 
> > 9 lb of pressure.
> > 
> > I then took another cap I had, rated for 15-18 lb, and it leaked like a 
> > sieve at around 11.
> > 
> > I believe I found part of my problem.  I'll be trying to find a local 
> > shop to change out the water neck.
> > 
> > Tonight adventure brought to you in photos, starting here:
> > http://www.teampanteraracing.com/index.php?option=com_g2bridge&view=gallery&Itemid=57&g2_itemId=3024
> > 
> > Asa Jay
> > 
> > Asa Jay Laughton, MSgt, USAFR, Retired
> > 
> > & Shelley Marie
> > Spokane, WA
> > 
> > 1971 Mach I Mustang  [ASA JAY]
> > 1973 Pantera L 5533  [ASASCAT]
> >    
> > ******************************     
> > http://www.asajay.com
> > http://www.teampanteraracing.com
> >  
> > 
> > 
> > 
> > Thomas Borcich wrote:
> >> This probably has been brought up many times, but it is the first mod I did to my car when I got it (a Dick Dreske suggestion)...replace the radiator neck on the tank with an American neck ($30 at most radiator shops) and then you can use an American pressure cap from any Ford or Chevy for $6-10 at ANY auto parts store nationwide. No guessing and if your out of town stop at Kragen, Pep Boys etc. and they will have one. I use the standard Stant 16 pound cap with the pressure release lever.
> >>
> >> Best regards,
> >>
> >>
> >>
> >> Tom Borcich
> >>
> >>
> >>
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