Hole behind freeze plug?

[Datsun AshLee]

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Hi everyone, if you read a previous post of mine, I had water running into the oil pan, anyway we pulled the oil pan off, put water in the block and looked to see where the water was coming from. Found out where the leak was and there is a small perfect hole (like it was drilled) right behind the front left side freeze plug, is this supposed to be like this? If so, is there supposed to be a plug or something there? The leak goes right into the area where the push rods are.

[Mackn367]

Do you have any pictures? Also what year/model/engine do you have?

[Datsun AshLee]

I tried to upload pictures but couldn't get it to work, it's a stock 70 1600 motor. The hole is in water jacket and leads to the place where the push rods are and oil drips in.

[Mackn367]

I tried to upload pictures but couldn't get it to work, it's a stock 70 1600 motor. The hole is in water jacket and leads to the place where the push rods are and oil drips in.

Your picture might be too large of a file size. Change the file size then try again. An easy way to do this is just email it to yourself and when it prompts you on what size file you want it to be just pic either medium or large. Don't pick "original size".

[C.Costine]

Many motors have holes in the block that are used during manufacturing for drilling oil galleries. During the process these holes are then plugged and never used again. With time the seating of the plugs can deteriorate until the plugs will leak, and if they get bad enough they can of course fall out. This is common enough that most engine rebuilders will as a normal part of the job replace the factory plugs with stainless steel ones. I don't know if the Datsun motor has these but that is what it looks like.

[Linda]

Wow, good catch, never heard of that before. A machinist should be able to plug it?
Linda

[keith0alan]

You should be able to thread the hole with a tap and install a plug, or bolt using Locktite 542 to seal it.

[notoptoy]

Is that for the road draft tube? If so, that may already be threaded, and just needs a bolt and to be sealed.

[spl310]

Not the road draft tube. They were located under the number four exhaust. Later engines may not be threaded. I have no idea what you have found

[Gregs672000]

Wow, who would know? Never seen or heard of anything like that. Looks like the problem though... plug her up and go I guess! Well done!

[keith0alan]

It looks like someone got frisky with the drill when removing the freeze plug.

[Linda]

If someone has an old block it would be interesting to see if there is anything like that hole inside and behind the freeze plug.
Linda

[greydog]

Sometimes the "why" matters less than the "what".
Why it's there probably doesn't matter. Factory? PO? Lightning?
What to do seems most critical.....as Keith suggested, thread the hole and put a hex head plug in it. Looks about 1/8 npt. Some permanent sealant on the plug and you've solved the issue.
Once the hole is plugged, you can move on, reassemble the engine (probably getting pretty good at it by now) and still have some summer left to drive the car.
Congratulations, you figured out the issue!
Dan

[roadsterdude1600]

Funny, I came across this thread while researching a replacement for the plug in the block (driver's side back upper corner) that is not included in the kit that Dean sells. I looked in my hole, and indeed it has a hole behind the plug, just like this one. By the way, it is a threaded hole (8MMX1.25) if I remember correctly. But I am not so sure it should be plugged. The ridge it is on appears to be the main oil gallery for the back of the engine, and maybe this hole is for extra oil to enter the push rod area?? I would have never looked if I had not found this thread. I did fins what I believe is a proper replacement for that plug - a 30MM brass piece from Dorman (565-100) but I have not yet installed it. Any other ideas about the hole? I would post a picture, but am having trouble figuring out how to do that. The "insert image" icon just prints [ing]/[img] on the page but does not allow me to search for or attach it..Really NOT a tehcie.....By the way, this is a '70 1600 block, if that matters.