Like the title says is it a bad idea to remove them when flushing the coolant or draining the cooling system? I recomended this as a precaution to someone when removing the intake and or heads to prevent the coolant from getting into an engine. You would have thought by the reaction I got that the world would come to an end. "You cant get them restarted", "would leak", etc. I have done this so many times that I couldn't begin to count.
IMHO ... that's why they're there!
If you can't get them to thread back in, replace them.
If they leak, teflon-tape them.
Cripes ... as a broke stupid kid driving "old junk" ... there were plenty of occasions when a boil-over or an upper rad hose sliced by the fan blade (broken mount -- caused by doing brake stands :mwink: ) meant adding straight water to the system.
When fall freeze-ups came along (thin ice at the top of a pail of water) it was fairly common practice to drain the rad overnight and re-fill it in the morning ... with more water. :embarrass
When the overnight temps started to get to the point where that pail of water started freezing almost all the way to the bottom, a guy would either pull the block drains or go buy some darn antifreeze!
I just changed the knock sensor on a 1992 chev van,they screw into
the block drain hole, no coolant came out until I poked a screwdriver into
the hole! I guess its time to Flush the cooling system!!
Yep, Everything that the other guys said. I like to replace them with a brass pipe plug that has a 9/16" hex and teflon based pipe dope or thread sealer.
I don't like the pipe plugs with the 5/16" allen for those drain plugs.
Have fun,Smokey
Thanks for the replies, I was shown this by a couple of old racers/rodders many years ago. In all of the times I had done it there was never an issue, I didn't think I was just being lucky.
Thanks!
Only thing that I would be afraid of is if they have never been out and the engine is in the vehicle. Snapping the plug off where I couldn't get to it to use an easy-out wouldn't be any fun. The ones in 1960's Pontiacs were steel and I always remove them during the rebuild and replace them with nice high quality brass ones so I can remove them easily later on when I flush out the system. While I have never broke an original plug, they have sometimes been very, very difficult to convince to turn after 40 years of never being removed. Pontiacs are also a rather small 1/8" pipe plug size that doesn't help anything.
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