Piston Broke Posted May 29, 2020 Share Posted May 29, 2020 I am fitting a replacement radiator drain tap to my 1940 MW, but the new one has a longer thread than the original. Due to corrosion in the radiator's female thread, I can't screw it in far enough to seat properly. Anyone know what the thread size is so I can try and get hold of a tap to clean it out? Quote Link to comment Share on other sites More sharing options...
Piston Broke Posted May 30, 2020 Author Share Posted May 30, 2020 Question answered by my local metal work suppliers, it's 3/8" BSP (prabably the same for a lot of British vehicles of this period). Here's a tip for the unwary though; when fitting a replacement drain tap, clean out the thread in the radiator first. The corroded cast iron or steel is hard enough to damage the brass thread on the new drain tap. Mine lost about 0.5mm of diameter when i tried to wind it in, and I didn't think I was using much force. Still enough thread left to screw home when the female thread was cleaned up however. Phew! Quote Link to comment Share on other sites More sharing options...
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