Hello everyone, returning here to the forum with a serious problem in my 1974 Datsun 620 with the l18 engine, it was approximately 4 years old (due to overheating). Everything was going well along the way, until I noticed that there was an antifreeze stain on the second spark plug, I checked it and realized that the antifreeze had not leaked into the piston, which seems like a very strange problem to me. Currently we are back to the initial problem of overheating (I don't know the reason for the overheating either) since I make sure to constantly check the levels, and a few days ago I was consuming a lot of antifreeze, until the temperature suddenly rose. and the problem with the spark plug got worse so I don't understand the cause of those failures. If you could help me I would greatly appreciate it. I am quite fond of my Datsun so I would like to repair it again, (I will soon be sending images so you can see the problem).