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Pressurized or non-pressurized radiator cap?

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  • Pressurized or non-pressurized radiator cap?

    I'm getting close to reinstalling my recently rebuilt engine (169 ci champion) and I had my radiator out for cleaning/rodding etc. I have a question about the proper radiator cap. I previously had a 4 psi (generic, aftermarket) cap on the radiator, and I noticed my parts manual lists two different ones from the official Studebaker line. There were pressurized and non-pressurized systems, but no distinction (like according to model/trim/serial #) as to which one I should use.

    I don't have any kind of overflow tank, just a overflow tube down to the bottom, that drains to the road if overpressurization occurs.

    Any ideas, warnings, etc. or does it make any difference?

    Las Vegas, NV
    '51 Champion Business Coupe G899965 10G-Q4-1434

  • #2
    The purpose of a pressurized system is to raise the boiling point of the coolant...doesn't change the temperature of the coolant, only the boiling point.

    If you feel the car will generally stay under 212 degrees F (slightly lower at higher elevations), no pressure cap is needed.

    A pressure cap will help you find any leaks and/or weak points in the cooling system [)], although a 4 pound cap is pretty close to a no pound cap.




    Dick Steinkamp
    Bellingham, WA

    Comment


    • #3
      Thanks Dick, I understand completely the theory behind each of them (otherwise I better give my Mechanical Engineer's License back!) however, I wasn't sure if there were certain systems that were originally designed to be pressurized, vs. those that weren't (e.g. based on engine # or overflow configuration). I guess if I pressurize it and find leaks, then I have my answer! The 4 pound cap was on it since I purchased the car, and since I am finally getting around to doing a lot of work on it, I just wanted everything to be right. Strangely enough, I've never had cooling system problems here in Las Vegas, even in summer. With all the additional horsepower (!!) I'll be getting out of my mighty rebuilt 6, I'll have to dissipate a few extra BTUs, so I figured it was a good time to clean out the radiator.

      Las Vegas, NV
      '51 Champion Business Coupe G899965 10G-Q4-1434

      Comment


      • #4
        One area to be concerned with is the top tank on the radiator.
        Most early 'low psi' radiators have top and bottom tanks that do not have 'ribs' built into them to support the tank sides at higher pressures. They can flex and eventually crack.
        Take your radiator to a good radiator shop and have him clean it and check it out...at the higher PSI. Ask him to look at the tanks and see how they react. If they are OK, he'll tell you. Besides... That's just good PM.
        Remember, there's a difference between a low psi cap, and a high psi cap...
        AND there's a difference between a vented, and non vented cap.
        A vented cap will allow outside air back in as things cool off and contract. A non vented (closed cooling system with a coolant recovery tank) will only allow coolant back in through the overflow tube, and not allow outside air back in.
        Jeff[8D]



        quote:Originally posted by vegas paul

        I'm getting close to reinstalling my recently rebuilt engine (169 ci champion) and I had my radiator out for cleaning/rodding etc. I have a question about the proper radiator cap. I previously had a 4 psi (generic, aftermarket) cap on the radiator, and I noticed my parts manual lists two different ones from the official Studebaker line. There were pressurized and non-pressurized systems, but no distinction (like according to model/trim/serial #) as to which one I should use.

        I don't have any kind of overflow tank, just a overflow tube down to the bottom, that drains to the road if overpressurization occurs.

        Any ideas, warnings, etc. or does it make any difference?

        Las Vegas, NV
        '51 Champion Business Coupe G899965 10G-Q4-1434
        HTIH (Hope The Info Helps)

        Jeff


        Get your facts first, and then you can distort them as much as you please. Mark Twain



        Note: SDC# 070190 (and earlier...)

        Comment


        • #5
          Radiator repairers often leak test at 2 psi air pressure, with rad under water. Insist on test pressure at whatever system pressure you will run (in your case, 4 psi).
          /H

          Comment


          • #6
            Speaking of coolant draining onto the road, a couple of weekends ago I had something happed that totally surprised me. I stopped at a stop light with my Mercury Topaz, had the ac running, took off and maybe 1/4 mile down the interstate I noticed the temperature guage needle climbing. Shut the ac off and turned the heater on, figured it was a stuck thermostat. That tactic delivered no heat whatsoever and the needle was pointing due north by the time I got it off the road. Ends up the little plastic thing retaining the plastic drain plug in the bottom of the radiator had popped out completely, dumping all the coolant on the road. I bet when that thing came out, it flushed the system in a hurry! To make a long story short, two hours later I was going again. The kid at the local O'Rileys knew exactly what I was talking about since his did the same thing. They carry those plugs as aftermarket parts for less than $4 and both Ford and GM use the same one. I think I'll get a spare and throw in the glove box just to be on the safe side.

            Comment


            • #7
              I, too, missed Studebaker cooling systems in Thermo 101 but my guess is that the pressurized vs non-pressurized distinction is not based on model type but on cars intended to be driven at higher altitudes. At 5000' water boils at about 200 degrees and a low value pressure cap would boost this back up to about 212 degrees. I looked in all my manuals for old Champs and could find nothing addressing this issue. I suspect this may have been a conversion made by dealers or service departments in the affected areas.

              Comment


              • #8
                I need to get new caps for two different re-cored Stude radiators and was wondering which ones would be recommended. One is a 63 Cruiser and the other is a 55 champion.
                Recommendation anyone??

                Thanks!
                64 Champ long bed V8
                55/53 Studebaker President S/R
                53 Hudson Super Wasp Coupe

                Comment


                • #9
                  the 63 should use a 13-14 lb. cap, the '55 may use either a 4 lb. cap or 13-14 lb. cap depending on manufacture date. only one will fit; the necks are different. The earlier 4 lb. radiator tanks will be smooth and "bulgy" while the later high pressure ones will have deep stiffening ribs in them.

                  nate

                  --
                  55 Commander Starlight
                  http://members.cox.net/njnagel
                  --
                  55 Commander Starlight
                  http://members.cox.net/njnagel

                  Comment


                  • #10
                    Since your '51 has been doing well with the 4 lb. cap, I'd keep it! Pressure ratings of these caps seems to be a well kept secret at Studebaker. I had to rely on aftermarket catalogs to confirm that part # 516009, 4 lb. pressure, is the standard cap for your car.
                    The non-pressure cap appears to be for use with the optional (and rarely seen) surge tank system.


                    Dwain G.

                    Comment


                    • #11
                      I suggest a double sealed 4 pound cap with an after market coolant recovery system.
                      The low pressure cap will allow the system to purge air out of the radiator and engine. That should make it run cooler.
                      The recovery tank will also prevent any puddles where you park. Antifreeze is poisonous. Small animals sometimes drink it, because it has a sweet taste.
                      Mike M.

                      Comment


                      • #12

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                        • #13
                          I understand all that, Neal (thanks ), but I still don't "get it" in real life applications.

                          I can't imagine any of us running our Studes at 250 degrees F. In fact, my newish GMC Sierra (my only non Stude with an actual temp gauge) runs at a consistent 210 degrees (hot days, cold days, towing, etc.)...and that is HOT compared to where we like to see our Studes run. Even it wouldn't theoretically need a pressurized system since the coolant never gets to the boiling point.

                          So...what advantage is a pressurized cooling system in a car (like our Studes) that run at 180-200 degrees F?. Raising the boiling point of the coolant with pressure doesn't seem to be a factor for us.


                          Dick Steinkamp
                          Bellingham, WA

                          Comment


                          • #14
                            My '57, which sports a '63 car 289 motor, runs with a 7 lb. cap and seems very happy whether idling in traffic or cruisin' down the hwy.

                            <h5>Mark
                            '57 Transtar
                            3E-6/7-122
                            </h5>
                            [img]
                            Mark Hayden
                            '66 Commander
                            Zone Coordinator
                            Pacific Can-Am Zone

                            Comment


                            • #15
                              quote:Originally posted by Mark57

                              [green][size=2][font=Comic Sans MS]My '57, which sports a '63 car 289 motor, runs with a 7 lb. cap and seems very happy whether idling in traffic or cruisin' down the hwy
                              Well, it might be happy with a 4 pound cap, a 15 pound cap, or a no pound cap [^]. If the pressure ONLY raises the boiling point of the coolant (ie...doesn't LOWER the temperature of the coolant), and the coolant never gets to the boiling point, does it really make a difference?




                              Dick Steinkamp
                              Bellingham, WA

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