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Posted By Discussion Topic: pressure test ? radiator     fordmerc 07-11-2013 @ 3:11 PM reply profile send p.m. New Member Posts: 180 Joined: Oct 2009 Any way to apply pressure to my '39 radiator while in the car in order to try to locate a leak? I have a water leak near the bottom and would like to locate it before pulling the radiator out.(It could be at the hose connection although I have already tried to seal that connection better) Since the overflow tube is at the top of the radiator and difficult to access from below, does anyone have a suggestion how to "pressure test" the system? The leak happens only after the car is hot and has been driven a bit; no leak at rest. TomO 07-11-2013 @ 4:14 PM reply profile send p.m. Senior Posts: 7264 Joined: Oct 2009 I have attached a hose to the overflow tube and clamped the end of the hose closed to put some pressure on the radiator. You do have to remove the pan under the radiator for access. It will also give you a better look at the radiator to see the leak. I have had problems with the reproduction hose clamps. They seem to stretch before they clamp the hose tight enough to seal it. You can use the worm drive clamps to seal the hoses. If you intend to put the car on the Concourse, tape the reproduction clamp to the hose, clamp the hose with the worm drive clamp and drive the car for a couple of hundred miles. Remove the worm drive clamp without disturbing the hose and use the repro clamp. Tom fordmerc 07-11-2013 @ 5:36 PM reply profile send p.m. New Member Posts: 180 Joined: Oct 2009 The way my under-radiator pan is attached ('39 Mercury), I would have to remove the radiator to get it out! I can slide a piece of tygon tube over the overflow tube, although I suspect it will not tolerate a high pressure. How high does the pressure in the radiator get on a very warm day going up a hill? I intend to drain the radiator, use a sealant on the hose connection and clamp hard, but it would be nice if I could confirm the source of the leak. supereal 07-12-2013 @ 7:28 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 We test radiators with a device that replaces the radiator cap. It has a gauge and a built in pump. Pressure can be supplied by the pump until the gauge reads the desired level. Then, the device is left in place while the reading is observed over time to see if it declines. If so, we inspect for exterior leaks. If none are found, we assume there are internal problems. Your best bet is to locate a shop with that device. They are not hard to find. Over pressurizing a radiator can cause damage, particularly if the radiator and/or heater core is old. Most household water system use as much as 60lbs. fordmerc 07-12-2013 @ 3:31 PM reply profile send p.m. New Member Posts: 180 Joined: Oct 2009 Yes, I tried a pressure test system as you describe, however since the overflow tube is not at the filler neck but at the top of the radiator, any applied pressure went right out the tube. ( I didn't think it would work but my friend insisted!) It sound like 10 psi pressure should bring out leaks and yet not do damage (?). My radiator had a new core when installed along with a rebuilt engine, and I have very few miles on it. I think if I could find a way to plug the overflow tube and then use that device I'd be able to test as described by TomO; I just need to assemble stuff and try. This message was edited by fordmerc on 7-12-13 @ 3:34 PM TomO 07-12-2013 @ 6:19 PM reply profile send p.m. Senior Posts: 7264 Joined: Oct 2009 If you can get your hands in the area where the bottom of the overflow tube is, slip a hose on it and clamp ie. I could not get my hands in that space, because the horns are in the way at the top and the pan was in the way at the bottom. You should be able to remove the pan without removing the radiator. It should be bolted below the frame as shown in the parts catalog. I would not go above 8lbs of pressure, you may pop one of the tanks. Tom This message was edited by TomO on 7-12-13 @ 6:23 PM supereal 07-12-2013 @ 6:57 PM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 Our pressure tester applies pressure below the overflow outlet. TomO 07-14-2013 @ 4:10 PM reply profile send p.m. Senior Posts: 7264 Joined: Oct 2009 Supereal, The 39 and 40 radiators have the overflow outlet at the top center of the upper tank and the filler neck is on the left side of the tank about 2" below the top. This was done to give room for expansion of the coolant. There is no way to pressurize the system without blocking the overflow pipe Tom

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