The 308/328 Coolant System – Anatomy of the Expansion Tank Cap | Page 3 | FerrariChat

The 308/328 Coolant System – Anatomy of the Expansion Tank Cap

Discussion in '308/328' started by Brian A, May 21, 2018.

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  1. ///Mike

    ///Mike F1 Veteran

    Dec 11, 2003
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    From the site to which Brian & I both linked:

     
  2. johnk...

    johnk... F1 World Champ
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    Again, how does the pressure rise if the vent is open? The point is that it's a poor concept that depends on too many variables. Basically it relies on the coolant starting to boil and some coolant (vapor or liquid) being expelled through the vent, in sufficient quantity and velocity, to close it. It's simply a case of over thinking and over engineering. Also from that web page,

    as in not anymore.
     
  3. ///Mike

    ///Mike F1 Veteran

    Dec 11, 2003
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    I did not endorse the concept, I merely reiterated the difference between full & partial pressure systems that Brian had tried in vain to get across previously. The *practical* takeaway is that *if* the 10331 cap is intended for partial pressure use then the 10231 cap that Brian pictured is a better choice for our systems. And since there's substantial evidence to suggest that the ~$30 OE caps are less robust than Stant caps, at <$6 delivered the 10231 cap seems like an excellent choice.

    Beyond that, I will leave you to argue with yourself, John.
     
  4. Brian A

    Brian A F1 Rookie

    Dec 21, 2012
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    There certainly is. I apologize for that. I think my informal characterization of the caps as Type 1, 2 or 3 is probably the least confusing (for me, at least).

    I can confirm that the 10331 does have the dangling “weighted” valve just like the 10231. The difference is that the 10231 is a plain twist-on cap while the 10331 has the red plastic lever.

    Per my “analysis” above, I had decided to use the Stant 10230 cap (with the spring-loaded vacuum vent valve) and NOT the Stant 10231 cap (the one with the unsprung “weighted” vacuum vent valve) that you ordered.

    I agree that the Stant caps are high quality replacements. To me, their simpler construction makes them a more robust design that the factory caps.
     
  5. johnk...

    johnk... F1 World Champ
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    Not arguing with anybody. But frankly the entire thread is a bit of a surprise to me. Are there actually 3x8s running around with "partial pressure" caps? Who decided that was the way to go when the originals clearly are not that type?
     
  6. Brian A

    Brian A F1 Rookie

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    While it was not my initial motivation for starting the thread, the thread came to address what has become the “common wisdom” that the 10231 “partial pressure” weighted “dangling valve” cap is the correct cap for the 3x8. This “common wisdom” comes from several sources including Ricambi America which sells the Stant 10231 "partial pressure" cap as the replacement cap.

    As I understand it, the factory caps are a spring-loaded vacuum valve design. This was one of the factors which made me decide to start using the Stant 10230 "full-pressure" cap on my car and NOT the "common wisdom" Stant 10231.

    ///Mike clearly understands these differences, so I am very interested in his rationale for reverting the conclusion back to the Stant 10231 instead of the Stant 10230.
     
  7. millsj

    millsj Karting

    Oct 17, 2011
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    I've actually wondered the same thing. If the vent is open, there is no way that it is going to build pressure.

    I've confused myself with all the cap numbers, but I replaced my cap from one that is open to one that is closed until there is a vacuum on it. My speculation is that it was dropping coolant out of the overflow tank because coolant was splashed up and out of the open vent while the engine was running. We will see what happens with the new cap. I haven't driven it enough to make a determination.

    Then again....I have no real knowledge of caps other than what is in this thread. :)
     
  8. johnk...

    johnk... F1 World Champ
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    You are correct. Factory caps were spring loaded. I mentioned that back in post 18 on page 1. I have the original that came with my car since I bought the car new in '85, and it lasted 25 years. Never cracked, though I have seen some that have. The rubber seal just got too hard to keep a seal. The problem with the original caps was (is) more that they were rated 0.9 BAR and once some slag builds up in the radiator and engine it runs a little hotter and when shut off or idling for a long time, the 0.9BAR is not high enough to prevent local boiling of coolant and the cars piss out the over flow. A 1.1 BAR cap usually corrects that. Where the "common knowledge" about cap type came from, I have no idea. But these things get passed down and eventually someone gets it wrong. Doesn't matter if it's Ricambi or Enzo himself. I don't know why anyone would put a weighted or partial pressure cap on a system without a recovery tank. Makes no sense. Not being argumentative, just makes no sense based on how they function.
     
  9. johnk...

    johnk... F1 World Champ
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    If air or coolant (vapor or liquid) is ejected through the vent at a high enough velocity it impinges against the "top hat" of the vent with enough force to close it.
     
  10. ///Mike

    ///Mike F1 Veteran

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    D'oh! Typo on my part. I'm blaming it on being cross-eyed from comparing too many radiator caps.

    I came to the exact same conclusion you did (independently, but through the same sources) so I ordered the 10230, as it functions the same as the OE cap (without the built-in fragility "feature") and it doesn't have the lever. The lever is actually useful but it looks out of place in a Ferrari engine bay. Other than being white zinc, 10230 looks close enough to OE to not draw a lot of attention to itself.

    Thanks again for shining the light of truth on this subject.
     
  11. ///Mike

    ///Mike F1 Veteran

    Dec 11, 2003
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    Been flushing the cooling system on my 348 and had just been using the factory cap during the process, even though it was cracked. Turns out the vent fell off into the expansion tank, and the lower rubber seal followed it in. Now I fully understand why Brian says he will not install factory caps. My car will not have one of those POSs again as long as I own it.

    I've run three fills of distilled water through the system and I'm still getting white powder out. The car came with clean looking green coolant in it and the PO had owned the car for a number of years so he must have always used green, because I wouldn't be seeing this much white powder if proper coolant had been used. I sure hope everyone here is running G-05 coolant or better.
     
  12. Glassman

    Glassman F1 World Champ
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    I agree......I have my holding tank cap removed and wrapped in tinfoil and then I stick a pin thru it.
     
  13. mike996

    mike996 F1 Veteran

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    "I sure hope everyone here is running G-05 coolant or better."

    The problem you are having is related to the water used, NOT the type of antifreeze. It's the minerals in the water that you re flushing out. IOW, distilled or de-mineralized water will prevent that problem once you get it cleaned out. No antifreeze, regardless of how expensive or "high tech" will prevent the problem. For that matter, if you are flushing they system periodically, there is no benefit to using anything other than standard antifreeze. Of course, if you don't want to drain/refill every year or two, then a long-life product makes sense.
     
  14. ///Mike

    ///Mike F1 Veteran

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    Mike, you may very well be right about the minerals in the water, although the PO had the car professionally maintained at his own dealership and I would expect that by now pretty much everyone knows to distilled water, especially pros. (I'm in the biz so I'm typically skeptical of other shops, but using distilled water is pretty much Cooling System Maintenance 101).

    As to G-05 coolant, I use it because of its superior corrosion protection for aluminum, period. That said, I see no reason to change coolant any more often than necessary. G-05 is the best water based antifreeze by far for our cars and it's very little more money than the green stuff, so why wouldn't I use it?

    In fact, after the major service is complete I'm thinking to go to Evans coolant just to cross one more maintenance worry off my list.
     
  15. mike996

    mike996 F1 Veteran

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    I know Jay Leno uses (or claims to use) Evans fir his cars but I'm not sure what real advantage it offers in general use. Is there some good objective testing around (not advertising copy from people trying to sell it) showing what it does better than water/AF? If Evans is Propoleyne Glycol, as their site claims, it has just a bit over 1/2 the efficiency of water's heat transfer ability. IOW, it would appear to be no advantage as far as moving heat compared to water/AF. I realize it has a higher boiling point but I don't see how that's any value since a properly maintained cooling system is not going to let the temps of standard AF/water mix get to that boiling point. But maybe I'm missing something?
     
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  16. ///Mike

    ///Mike F1 Veteran

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    I think its big selling point is corrosion resistance since it's waterless. I haven't researched it to the point of being completely sold, but from what I've seen so far it's worthy of consideration. Until then, G-05 + distilled water FTW.
     
  17. kcabpilot

    kcabpilot Formula 3

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    FWIW I have the heads off my car right now which has 60,000 miles on it and, as far as I know, has never used anything other than regular old green antifreeze and I see virtually no signs of any internal corrosion anywhere. I was surprised at how clean it looks.
     
  18. thorn

    thorn F1 Rookie
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    I think Evans is a solution to a problem you shouldn't address by using Evans.
     
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  19. Brian A

    Brian A F1 Rookie

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    The "what is the right cap" question just popped up again, which reminded me to copy/paste/edit something from yet another thread on expansion tank caps to this master thread...

    We concluded in this thread that the Stant 10230 is the correct cap for our cars. The reason it is the best cap is that it has a spring-closed air-return valve rather than a "dangling" valve. With the spring, the expansion tank immediately begins to pressurize when the coolant heats and begins to expand. The air in the expansion tank is compressed and not released to the atmosphere. As the system cools again the pressurized air just re-expands to its cool volume. No new air is ingested. Of course, air and coolant will be vented through a different seal on the cap should the coolant system pressure exceed the caps rated pressure, which is 1.1 bar (16 psi) for the Stant 10230.

    The other incorrect "dangling valve" cap (the Stant 10231) allows the air in the expansion tank to immediately vent as the coolant heats and expands. No air is compressed. The valve closes only when the coolant level touches the dangling valve. This is only a minor issue but causes two minor problems. First, the valve may not close from the first drop of coolant, so the car may drip a tiny bit of coolant each time. Second, the cycle of purging and refilling introduces fresh oxygen into the expansion tank which then can dissolve in the coolant. This increases the oxidization (corrosion) and aluminum oxide precipitation in the cooling system.
     
  20. BigTex

    BigTex Seven Time F1 World Champ
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    I guess my post is in that "other thread" I went to NAPA told them "cut the crap and give me a 16# NON vented cap", and got one...

    I put the number up as it was not Stant...
     
  21. vespaholic_com

    Apr 22, 2009
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    I read through this thread and I gather that the original factory coolant system cap was a 4-ear.
    Am I correct?
    I just ordered a 137644 from a parts supplier expecting a 4-ear but got a 2-ear.
    Picture on their site was the 4-ear though.
    Parts supplier is telling me that in 1982 it could have been either.
    Just depends on what the worker grabbed at the factory.
    I'm calling BS on that, but I figured I'd check with you guys.
    Thanks in advance!
     
  22. miketuason

    miketuason F1 World Champ
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    The old four ears .09 bar was updated to the four ears 1.1 bar
     
  23. rjlloyd

    rjlloyd Formula Junior
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  24. Brian A

    Brian A F1 Rookie

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    Below is a picture of the original Italian 0.9 bar cap placed beside an installed Stant 10230 1.1 bar cap. Both have four "ears", but the shape is a bit different.

    As I understand it, for FCA Concours Judging any functional cap is acceptable because it is considered a wear item. Even those ones with the useless red flippy lever are okay.

    It may be difficult to find an exact circa 1980 factory-original cap since substitution with other brands and styles has not been a concern for most people.

    Image Unavailable, Please Login
     
  25. lm2504me

    lm2504me Formula 3
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    #75 lm2504me, Feb 22, 2022
    Last edited: Feb 22, 2022
    `My experience with the square radiator cap which has has the seal / vacuum valving swaged into the radiator cap. I have purchased these new from Ferrari and other parts suppliers and have them arrived defective. It may have cracks in the swaged area which does not allow the coolant system to pressurize and the bottom piece with the slots will fall out. A recent purchase of a Vetrosina 308 by my friend had a defective radiator cap like the photo. He ended buying it already cooked by the previous owner. Coolant was in the oil pan due to overheating. The head gasket was compromised. He purchased two new ones. They were both defective. They would not hold pressure when tested with my radiator cap tester. He returned them and purchased the 1.1 bar with the disk sealing on the rubber gasket. Always do a pressure test of a new radiator cap to verify it is working to 1.1 bar or its rated pressure.
     

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