1939 President Posted April 23, 2020 Share Posted April 23, 2020 How much, if any, cooling system pressure should a late 30's early 40's flathead, straight eight have. Trying a DIY radiator repair and thought I'd pressure test it with air, WITHOUT blowing it apart. Any Help? Link to comment Share on other sites More sharing options...
nickelroadster Posted April 24, 2020 Share Posted April 24, 2020 Radiators did not use pressure until sometime in the fifties. I would use no pressure. 1 Link to comment Share on other sites More sharing options...
Larry Schramm Posted April 24, 2020 Share Posted April 24, 2020 I believe they are checked with maybe 1-2 psi only. 3 Link to comment Share on other sites More sharing options...
Ben Bruce aka First Born Posted April 24, 2020 Share Posted April 24, 2020 12 hours ago, nickelroadster said: Radiators did not use pressure until sometime in the fifties. I would use no pressure. John Karmazin , working for Harrison Radiator, invented the pressure cap which was first used on the 1939 Buick. Ben Link to comment Share on other sites More sharing options...
dustycrusty Posted April 24, 2020 Share Posted April 24, 2020 Depends on the manufacturer -- by your name a Studebaker President 8? It looks like they went to a pressurized system in 1941, so a cap with a 3-7 lbs pop-off pressure is required. Even in an unpressurized system there is a modicum of pressure. As your coolant heats up it will expand slightly- the hotter it gets, the more it will expand until it gets hot enough to cause some liquid to separate into a gaseous form (the bubbles in boiling water). Pure water will boil at 100C/212F at atmospheric pressure, but pressurizing the system (and using coolant additives) will raise the boiling point of the coolant, hopefully beyond the operating range of the engine it is attempting to cool! Non pressure radiator caps allow the coolant to escape the upper tank as it expands beyond the height of the neck, a pressurized cap will keep the coolant contained until it hits a pre-determined release pressure. If you want to pressure test a radiator, I probably wouldnt exceed 3 lbs PSI- use the rubber stopper and plunger pump type tester with integral PSI gauge or drill an old cap , install a Schrader valve in the hole and give it a few pumps with an old-fashioned tire pump- OR take it to a radiator shop and have them do it while you watch (they're insured....). Link to comment Share on other sites More sharing options...
Larry Schramm Posted April 24, 2020 Share Posted April 24, 2020 1 hour ago, dustycrusty said: OR take it to a radiator shop and have them do it while you watch (they're insured....). And they can put in in a tank and look for leaks/bubbles. They can fix it right then and you will be good to go. Link to comment Share on other sites More sharing options...
1939 President Posted April 24, 2020 Author Share Posted April 24, 2020 Thanks for the input, think I'll go with maybe 1+ lbs of pressure. You guys are a fountain of knowledge, now can someone direct me to the Fountain of Youth? Link to comment Share on other sites More sharing options...
keiser31 Posted April 24, 2020 Share Posted April 24, 2020 34 minutes ago, 1939 President said: Thanks for the input, think I'll go with maybe 1+ lbs of pressure. You guys are a fountain of knowledge, now can someone direct me to the Fountain of Youth? I heard it was in Florida.... 1 Link to comment Share on other sites More sharing options...
sagefinds Posted April 25, 2020 Share Posted April 25, 2020 Here is a way you can put a little head pressure on it without trying something with air pressure. Plug off the bottom outlet by clamping a short piece of hose on it and something like a pipe cap clamped inside the other end. Have a good sealing cap on top,then with a piece of same size exhaust pipe with a hook in it or put together with PVC pipe clamped on the top inlet,run a standpipe up three or four feet clamped to a post or something so it won't lean over, fill it up with water and watch for wet spots before your eyes and hope there aren't any. Good luck. 1 Link to comment Share on other sites More sharing options...
1939 President Posted April 26, 2020 Author Share Posted April 26, 2020 Saw your response, went to the shop, put together this set-up and let her rip. The upper brass tank had a 1 1/2" hairline crack. Used propane torch and body solder, 30/70, NO LEAKS! Thank you! 2 1 Link to comment Share on other sites More sharing options...
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