Datsun 620 74, antifreeze stain on the second spark plug and overheating

[Derek Harris]

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).

[datzenmike]

Head gasket failure.

 

I've changed three maybe four if helping someone else. Just wrench turning. Last one cost about $30 for the gasket. But before we go any farther, I don't know what your plans are.. Do NOT remove your cam sprocket until you have found out how to prevent the timing chain tensioner from popping out. If it comes out it can't be fixed without taking the entire front of the engine.

[Derek Harris]

Ok, very good, the truth is that it puzzled me quite a bit, since as I had mentioned before, this failure occurred just when the engine was being fixed, perhaps they did some bad job.