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Radiator Caps

Discussion in '308/328' started by mike996, May 15, 2019 at 6:45 AM.

  1. mike996

    mike996 F1 Veteran

    Jun 14, 2008
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    Mike 996
    While doing some other work, I have found that the cooling system on my 328 doesn't seem to pressurize. The normal pressure build-up seems to be being vented by the small disc valve that is on the cap to allow coolant to return to the system. Since there is no overflow tank on these engines, it SEEMS to me that the proper cap should EITHER have no such disc at all OR the little disc should be lightly spring loaded closed as opposed to hanging open. If it's open, I don't see how the system can pressurize with a normal, slow increase in coolant volume that occurs as the engine warms up and the coolant expands.

    I am using a typical 15PSI Stant cap. using this model cap since shortly after buying the car in '08 when a local "expert exotic" shop changed the coolant/cap. I've since replaced the coolant/cap several times but I'm now thinking the system hasn't been pressurizing for 11 years! ;)

    Any thoughts re proper Rad caps?
     
  2. Brian A

    Brian A Formula 3

    Dec 21, 2012
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    1983 US 308 GTS QV
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  3. Saabguy

    Saabguy Formula 3
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    Mar 28, 2012
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    Shreveport, LA
    Brian, that was almost a year ago! There is plenty to forget in a year. ;-)
     
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  4. nerofer

    nerofer F1 Veteran

    Mar 26, 2011
    9,719
    FRANCE
    Being french (nobody is perfect) I have to say that I was somewhat puzzled by the title of Mike's thread: to me, a radiator cap is not the same as the expansion tank cap; and Mike concludes by saying "rad cap".
    Confusing, at least to my french mind...what is discussed here? The cap one the expansion tank?

    Rgds
     
  5. mike996

    mike996 F1 Veteran

    Jun 14, 2008
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    Sadly, just because I participated in the discussion doesn't mean I remember anything about it! :(

    In reality, I just let the whole issue go until yesterday when I saw coolant draining from the overflow tube when the car was sitting in the driveway idling (at operating temp, fans cycling normally). I carefully opened the cap to find no pressure at all - the coolant had simply expanded to the level of the drain tube and was dribbling out via the open "dangling vent."

    Despite the cost difference, I ordered a cap from Ricambi; I figure it HAS to be right - they've never let me down! :)

    I referred to the cap as a radiator (rad) cap as opposed to expansion tank cap simply because it is usually the term used for them here (US) regardless of whether they actually cap the radiator or an expansion tank. Sorry for any confusion.
     
  6. nerofer

    nerofer F1 Veteran

    Mar 26, 2011
    9,719
    FRANCE
    Thank you Mike, it makes more sense to me now.
    I have an new OEM 0,9 bar, as per OEM original, on both cars; they work, no need to upgrade to 1,1 bar.
    I had some dribbling and overflowing after a trip or the other, not every trip, at the beginning of ownership until I began to think that the car was only spitting out the excess I poured in over the recommended level. Guess what? When I followed the Owner's Manual instructions and let coolant stabilise at exactly the recommended level (exactly half the tank, 6 cm under the top of the filler's neck) the cars stopped spitting coolant for good. Never occured again.
    Rgds
     
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  7. mike996

    mike996 F1 Veteran

    Jun 14, 2008
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    Mike 996
    Yes, I know that my system was a bit overfull from my last coolant change so I am not surprised at coolant spitting out via the tube but that should only happen when the pressure exceeds the cap's rating, but since it was dribbling out with no pressure in the system, that's why I revisited this issue. Clearly, I have had the wrong type of cap on the car since the shop installed a new one at its first coolant change back in '08. I just bought the same cap whenever I decided to replace it, assuming they must have known what they were doing... And we all know about "assumptions," don't we? ;)
     
  8. nerofer

    nerofer F1 Veteran

    Mar 26, 2011
    9,719
    FRANCE
    Доверяй, но проверяй

    (Russian saying; pronounced more or less "Dovéraï, non proveraï"; meaning "trust, but verify"; President Ronald Reagan learned it during his Presidency when he negociated with the Soviet Union, and was particularly found of it)

    Rgds
     
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  9. Brian A

    Brian A Formula 3

    Dec 21, 2012
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    1983 US 308 GTS QV
    It will be interesting to see whether they send you a Stant 10231 (dangling valve) or Stant 10230 (spring-loaded valve).


    I have never seen the Service Bulletin but I have read in several places that Ferrari issued one recommending increasing pressure to 1.1 bar. No matter: if 0.9 bar works, no argument to be made!

     
  10. miketuason

    miketuason F1 World Champ
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    Feb 24, 2006
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    Mike
    I once replaced my original 0.9 cap to the 1.1 bar cap and it started to leak coolant through the overflow tube so I went back to my 0.9 bar cap and it hasn’t leak since, it has been 8 years now and it’s still working great.
     
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  11. lm2504me

    lm2504me Formula Junior
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    Aug 26, 2004
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    Richard
    I bought one of these and test my coolant system will hold pressure (helps find leaks) and all my radiator caps open at correct pressure.
    I have found new caps to be bad.

    Image Unavailable, Please Login
     
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  12. mike996

    mike996 F1 Veteran

    Jun 14, 2008
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    :)
    I ordered this one: https://www.ricambiamerica.com/expansion-tank-cap-radiator.html They show a Stant available as well though it is a 1033. They don't show a 10231 or a 10230 for the 328 listings. It'll be interesting - should be here today since I specified 2 day shipping!
     
  13. mike996

    mike996 F1 Veteran

    Jun 14, 2008
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    Thumbs up!! Ricambi cap works as the system requires!! I "tested" by doing the same thing as a few days ago. I "overfilled" the expansion tank so it was at the same level as it was when it was dribbling out coolant as it expanded to reach the overflow tube. This time - no dribbling whatsoever and when the pressure got to the point where it exceeded the cap's 1.1 bar, it spurted out of the overflow pipe for a few seconds as you would expect, rather than dribbling constantly. Tomorrow, after the engine is cold, I'll remove coolant from the tank to get it down to the correct level.

    FWIW, though it's the same Ricambi part number, 137644, the cap does not look like the one in the Ricambi pic that I posted. It has a brass-colored square cap and a standard-looking disc valve that is spring loaded shut. It looks to me like the original style cap that is referred to in Ricambi's info:

    ** PLEASE NOTE, THESE CAPS (FROM FERRARI) NOW HAVE METAL 2 METAL EARS FOR OPENING, WHILE ORIGINAL PRODUCTION CAPS WERE SIMPLE SQUARE SHAPED VERSIONS. We do not have the old style caps available at this time **

    So, since the square cap I received has the same Ricambi part number, it looks to me like they now have the original style caps but haven't updated the info.

    And NEO...the bag is labeled correctly as "Expan Tank Cap," NOT "Radiator Cap!" :)
     
  14. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Two Time F1 World Champ
    Rossa Subscribed Owner

    May 4, 2001
    28,177
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    Tommy
    I went from a 0.9 to a 1.1

    That was Sept 1997 and about 60,000 trouble free cooling system miles ago, in the deep south.

    So don't fear the 1.1
     
  15. mike996

    mike996 F1 Veteran

    Jun 14, 2008
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    Mike 996
    I've had 16 PSI (1.1 bar) caps since shortly after I bought the car in '08 but since the 'dangling valve' caps never allowed the system to pressurize, they were actually 0 PSI caps! Now I have a 16 psi cap that actually works.


    Oh...forgot the best part about the Ricambi cap - a free pack of Chips Ahoy cookies! :)
     
  16. Martin308GTB

    Martin308GTB F1 Rookie
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    Jan 22, 2003
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    Martin N.
    Taking into account the manufacturing tolerances and how cheaply made these caps are, this 0.9 vs. 1.1 bar thing is a joke.
    Tolerances on the header tank neck also matter.
    I had a (genuine Ferrari part) 1.1 bar cap, where the rubber seal had no contact inside the tank neck. No wonder, that the system didn't pressurize, but pumped coolant onto the floor instead.

    Best from Germany
    Martin
     
  17. waymar

    waymar Formula Junior

    Sep 2, 2008
    860
    Northeast, PA - USA
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    Wayne
    Just purchased a Stant 10230 16/lb looking forward to what happens as I have the Stant 13/lb now. Car 308GTSi
     

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