boiling after 3 miles but...

Discussion in 'Small Block Mopar Engine' started by Moparbaker, Jul 6, 2018.

  1. Moparbaker

    Moparbaker Active Member

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    I've put a Weiand Stealth alu intake on my -89 318 & carb & waterpump & radiator is new.
    Now then: every time I go for a drive it overheats after 3 miles & so I refil & then it don't! & I've got a manual switched electric fan on full + the inside heater & fan on full too, but it aint helping a bit.
    I can go on for 200 miles after refill & no overheating... Just going to work or back home from work means stopping after 3 miles to refill the radiator. If there's a air-pocket or bad ingition timing it shouldn't change after re-fill, right?
     
  2. General Disarray

    General Disarray Well-Known Member

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    Do you have a fan shroud?
     
  3. inertia

    inertia Well-Known Member

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    Hi, not to be rude, but we just got thru 2 - week long, lengthly threads on overheating. In an effort to shortcut your answer, I respectfully suggest you look in the "cooling section",and a quick review. The answer you seek is there, cuz EVERYthing was covered. Thanx very much, Cheers
     
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    • Moparbaker

      Moparbaker Active Member

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      Alright, thanx!
      & no, I don't fiind info rude... ;)
      (Thou I was just gonna ask about the radiator cap, I think it ought to let out the hot air when the water is expanding but it don't...)
       
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      • MOPEkidD-3

        MOPEkidD-3 Torsional Member

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        Sounds like an overflow tank might help, you just have the rad puking straight to the ground?
         
      • Moparbaker

        Moparbaker Active Member

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        There's a overflow tank there too.
         
      • AJ/FormS

        AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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        Just overfilled is all? Or defective radcap?
        With a recirculating type system
        When the coolant gets hot it expands,and about a half a liter is forced out of the rad into the expansion-tank;this is normal. Then when the engine cools, the contracting fluid pulls the previously pumped out fluid back in. The rad cap is in charge of this event,
        and the hose between the filler neck and the expansion tank, and into the tank to the bottom of said tank, has to be one continuous system in order for this to work. If the contracting fluid pulls air in instead, eventually you will have an air pocket in the top of the rad about 1 inch deep. If your rad is a 1970 or older balloon-top design, it was meant to operate like that so it's no big deal. In about 1972 or 73 the rads were redesigned and had smaller tanks. These rads will still operate this way, with the air-pocket at the top, with a stock engine. As the engine performance increases, the engines tend to run warmer, and if you don't keep an eye on the fluid level, you could (not will) eventually get into an overheat situation. At 420 hp, I haven't yet had a problem with my 1973 square top rad, operating in the old mode where the expansion tank is just a puke-tank. And I run a 7psi non-recirculating type cap. The top tank in my system has become the recirculation tank.
         
        Last edited: Jul 6, 2018
      • Moparbaker

        Moparbaker Active Member

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        Thanx, I'm gonna look over the stuff tomorrow, gotta be something that's wrong with the cap since it aint letting any air out. I reckon the spring is way to hard, it feels harder than other cap's springs I have laying around, but sadly they don't fit.
         
      • brian6pac

        brian6pac Well-Known Member

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        Thermostat in upside down? I've seen it happen.
         
      • BigBlockMopar

        BigBlockMopar BigBlockMember

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        Boiling within 3 miles, says stuck/sticky thermostat to me.
        No amount of 'radiator-issues' could cause coolant to boil within such a short time unless the thermostat won't open (quick enough).
         
      • lomchivok

        lomchivok Well-Known Member

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        I bought a cap here a while where the sealing stem was too long. The radiator would discharge into the overflow tank but couldn't suck coolant back when cooling down. A noticeable vacuum was present when the cap was removed cold. No overheating problems but a different cap fixed it.
         
      • AJ/FormS

        AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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        There are two types of caps at the parts store; those for the older puke-systems, and those for the recirculating systems. And they can both be had in a multitude of pressure ratings. Be sure your expansion tank is matched to your system. In the recirc type, the hose has to draw from the bottom of the tank. The tanks usually have a pick-up straw cast integral with the tank, and an external nipple connected to the straw. You can convert an older tank simply by drilling the plastic cap and stuffing the hose all the way down to about 1 inch from the bottom.
         
      • AJ/FormS

        AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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        When OP says boil, I read pukes to atmosphere, so 3 miles sounds about right to me at this time of year, even in Sweden,for the stat to open. The coolant in the rad will still be cold. When the hot coolant finally bursts thru the stat at hiway speed, the coolant will all mix pretty much instantly and expand , blowing the excess into the overflow tank.
        If it pukes to atmosphere, you have the wrong cap, the wrong rad, or a defective cap/rad sealing surface.
        But yes, the stat could still be lazy.
         
      • Moparbaker

        Moparbaker Active Member

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        Guess what... I've already tried without thermostat already quite some time ago, sorry for not writing that, I thought it was an obvious thing to do.
        & it doesn't matter with or without thermostat, it's the same...
         
      • BigBlockMopar

        BigBlockMopar BigBlockMember

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        Then I would look into a leaking headgasket depending on how much water is to be refilled during every drive.
        Because you mention you have to refill the radiator everytime, would tell me there's enough coolant leaking away somewhere to cause overheating the next you drive it.
        That alone gives the impression the coolant system is very marginal in the first place.

        How much water needs to be added everytime anyway?
        Are there wet-spots under the car?
        Does the oillevel rise, or look milky?

        If your avatar image is still correct, your underdriven waterpump doesn't help the situation either if the coolant level is low. But this won't cause coolant to boil in such a short time.
         
      • Moparbaker

        Moparbaker Active Member

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        When I notice the temp is rising there's water squirting out bigtime & that's when I stop & refil with about 5-6 liters & then it's alright. So yep: there's water under the car + a track behind too.

        The thing I really wonder about is why it's alright after the refill?
        It's as if the cap don't let out the warm air & then it overheats fast in this hot weather, 25-30 C / 77-86 F.
         
      • General Disarray

        General Disarray Well-Known Member

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        When you say you can drive 200 miles with no issues, is that like constant driving, no stop and go?
         
      • oldkimmer

        oldkimmer Well-Known Member

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        Then try a new rad cap, their only a few bucks. Match it to ur system. Kim
         
      • inertia

        inertia Well-Known Member

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        What are the rads inlet and outlet temps?
        If the rad is cooling properly, and in fact it isn't boiling, but is instead building pressure from another source, and when that pressure reaches the cap release pressure, it discharges non-overheated water out the overflow, till, there isn't enuff coolant left, it then starts to overheat ! !
        This is the case with most head gasket related overheats..
         
      • TrailBeast

        TrailBeast Slightly Twisted Member

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        If you have a return type cap you might get another one.
        Sometimes the return valve hangs open as the system is cooling down from the last drive and then sticks letting the coolant bypass it before the cooling system gets up to pressure.

        If you don't have a return (aka recovery system) you should get one.
        The recovery system keep the cooling system completely full all the time when working correctly, and that little valve closes tight a lot better when coolant is up against it instead of air.
         
      • oliver

        oliver Well-Known Member

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        Did it do it with the old water pump?
         
      • Moparbaker

        Moparbaker Active Member

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        It was the cap.
        & the overheating started just a few weeks ago, long after the new waterpump & radiator was installed, the change I did just before the overheating started was the inlet manifold & shorty headers, the rest was as it's been for a long time.
         
      • oldkimmer

        oldkimmer Well-Known Member

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        Glad I got her fixed. Just think, a 5 dollar cap could of been the demise of ur engine. Kim
         
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        • dubree 61

          dubree 61 73 swinger

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          I think your on the right track that makes more sense to me than any thing else
           
        • Moparbaker

          Moparbaker Active Member

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          In #16 + other stuff I've written it's possible to read & maby even understand that no water leaves exept when overheating...
          & General Disarray, it's more or less constant driving, only stop for buying stuff or filling gas, so it doesn't cool down.

          Anyway: Problem solved!