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Radiator drain cock

The above part on my 1988 Chevy Silverado broke off. I bought a replacement and it was easily installed. This is a plastic part. It seems, however, to loosen itself when the car sits overnight. When I tighten it before taking the vehicle out (while it’s warming up) it holds well. When I don’t, it seems to loosen up and begins to leak. Is there any way to ensure that I don’t have to check this every time I take the truck out?

Try some “Lock Tight” or better still, a sealer that will give you a soft hold. You don’t want to over tighten and strip the threads, but the threads obviously need help.

Agree. Loctite makes a variety of products that are designed specifically for a situation such as yours.

will I have to drain the system in order to use Loctite? This part comes with a housing that would be very difficult to remove and the threaded piece itself clicks in before you tighten it. Can this be applied without removing the entire part?
thanks.