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1939 Cadillac Radiator Cap Question

Started by clockman1700, February 08, 2012, 11:15:13 AM

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clockman1700

Hello,
         Can anyone help me with a question regarding the radiator cap on a 1939 Cadillac 75. I believe that I have the original cap which has the vented stem and brass bottom on the cap. My question is, should there be a seal placed in the radiator neck to prevent normal heat expansion overflow? It seems to me that the brass bottom of the cap should be sealing against a rubber washer, not the metal of the radiator neck. Any help would be greatly appreciated.
                                                                                     Thanks Barry
BarryTorrente                                                                                                          1939 Brunn town car 75

R Sotardi #11719

The 39 & 40s used a 7# cap same as the 40-47 Buick, 50 -53 Hudson. The caps were originaly AC 13 7# then in the early 50s AC changed their listing to RC-3( GM part # 850797) the original part number was 846713 ( in the 40s) and the last two numbers were the number on the cap itself, hence 13, 7# AC on the ear. They were all cadmium plated. Not blue red and silver as those came out in the 60s as replacements. The top seal of the cap, that pushes against the 1" deep radiator neck,  is brass. The sealing action is the rubber ring at the bottom, that pushes against the ridge inside the neck.

clockman1700

Hi,
    Thank you very much for this information. I thought that there should be a rubber seal, and I can only assume that the rubber on my cap deteriorated, but when I examined this ,I could not see any area where the seal might have fit in between the metal sections. I replaced it for now with a NOS, but will work on the original to restore it for use.
                                                                                     Thanks,
                                                                                               Barry
BarryTorrente                                                                                                          1939 Brunn town car 75