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Radiator is foaming when up to temperature.


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I have a 1928 Dictator and have been checking all fluids regularly....and have noticed when checking the radiator level, it has foam at the top. Is this normal or do I have a problem of sorts?? Thanks for any insights you may share!!!!!!

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You could be experiencing a head gasket leak. Remove your fanbelt and then run the engine for a few minutes and check the radiator for bubbles. If there is more bubbling without the water pump turning over it may be head gasket replacement time? You could try to retorque all the head bolts to the same ft/lbs and see if that helps reduce the bubbles. A can of cooling system sealer might cure the problem but plan on pulling the head and observe where the gasket appears to not be sealing tight. It might indicate the head has warpage and requires a resurfacing at a machine shop and/or a new head gasket. Of course the worst case could be a cracked cylinder head. Is the car 6 or 8 cylinders?

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stude8 gave some insightful information. By removing the water pump belt you not only stop forced flow but also eliminate the possibility of the water pump suction pulling air into the system at the suction hose circuit. It is rare but has been known to happen. If there is compression entering the system, a good check is to put a hose on the radiator overflow nipple and route it into a clear plastic drink bottle filled halfway with clear water. With engine cold and cap resealed, run engine up till operating temperature stabilizes. As the system warms, expansion will pressurize the system and air bubbles will appear in the bottle. (don't top off radiator before the test, it needs the normal amount of air space for expansion) As thermostat starts regulating and the temperature levels off, the bubbles should slow and finally stop as normal expansion has ceased pressurizing the system. After that, only an occassional bubble should appear. If there is a continuous stream of bubbles after temperature levels off, then that may indicate compression entering the system. Be sure the lower radiator hose is good and sealing at both ends before tearing into the engine. If it has a heater hose also connected to the water pump suction, it may be suspect also. If this test indicates no compression or over pressurizing, then consider flushing the system good and filling with fresh coolant mixture. PS. if you have an electric fan, the temp will go up and down with the fan cycle which will cause a pressure fluctuation in the cooling system and could possibly pull water from bottle and then back into it with the temperature fluctuation.

Edited by TexasJohn55 (see edit history)
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I agree with what has already been said, however, from personal experience (learned the hard way) I have one additional comment. Do you use anti-freeze/coolant in your radiator? Your coolant system in a 1928 is non-pressurized. If you add modern anti-freeze/coolant to your system it will cause the coolant to foam.

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deburt65: I apologize for wandering off into unknown territory. After posting, I realized that you probably did not have an overflow hose on your radiator and therefore could not test for compression with a bottle and hose. The theory is still good but useless for your application. I shall stay out of this discussion and leave it to more knowleadgeable owners of the 1928 era automobiles. It looks like you already have some capable folks helping. Regards, TexasJohn

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Studeboy....This is true about the pump running off the accessory shaft....but if it has a leak, could it be the source of bubbles/foam in the radiator??? I have had a small leak on the shaft, big nut area, but not a serious leak so haven't been too concerned....enough to address it....

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I am not sure. I also have a 28 dictator. I run anti freeze in it and if I over fill the radiator I get foaming but just a slight amount. It could be your pump is forcing air into the system or it could just be how much water your water pump is moving? The tests other have mentioned here are all good . I just don't see how you could do them on a 28 dictator. If you disconnected the accessory shaft your oil pump, distributor and generator would also be disconnected so the engine wouldn't run. The coolant tester seems like the only possibility.

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Studeboy.......I usually fill my radiator up to within 1 inch from the top, so maybe I have over filled it, thus the foaming. However, it was lower than that the last time I checked it, and there was a fair amount of foam. I guess, as long as it doesn't over heat, I should be ok....I hope.....but, I will still be asking anyone who owns these older cars and has more experience than I have.....but thanks for sharing.....

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