Coolant in the oil.

[youztheclue]

I rolled the dice and I lost the bet:(

[Dave WM]

since you are going to have to re do it, you should

clean head and block of any remnants of head gasket, DO NOT USE one of those abrasive 2" wheels to clean, rather a lot of elbow grease, a PLASTIC BLADE razor scraper (at least on the head, the block is less likely to be damaged by a regular metal scraper), lots of gasket remover goo etc... THEN check for flatness of he head. IF its ok carefully follow the directions in the FSM regarding how to torque in sequence and amount of torque applied in multiple steps.

[chaseincats]

To throw a bit of contrast in here I don't think the broken bolt is the problem here.  My car had 2 broken bolts and ran for years without overheating.

[Dave WM]

there is a basic assumption that the block and or head is NOT cracked. So CC you had 2 broken head bolts? how did you know that? you installed the head with missing bolts? They broke during installation?

[chaseincats]

1 minute ago, Dave WM said:

there is a basic assumption that the block and or head is NOT cracked. So CC you had 2 broken head bolts? how did you know that? you installed the head with missing bolts? They broke during installation?

Not sure when they broke - the head has not come off while I've owned it.

When I changed the valve cover gasket I noticed the front passenger-side bolt had its head sheered off so I easy-outed that and changed it (the bolt's head was resting behind the timing belt tensioner which was terrifying).

The second broken bolt is 1 of the 4 cam tower bolts which is broken to this day because it is apparently snapped way deep in the head/block.  I only noticed it while re-torqueing the head bolts when I was going through the engine tuneup chapter of the FSM.

[youztheclue]

The bolt was snapped already and is the old bolt. I have a fresh one ready to replace it. I milled the head and all that. I just took everything apart. It could be the front cover gasket leaking? I'm not sure, the thing is it my first time with z's and having a project car like this.

[siteunseen]

32 minutes ago, youztheclue said:

The bolt was snapped already and is the old bolt. I have a fresh one ready to replace it. I milled the head and all that. I just took everything apart. It could be the front cover gasket leaking? I'm not sure, the thing is it my first time with z's and having a project car like this.

You should buy this book if you're going to keep the "habit" we all have.  It's for rebuilding but also a good reference after the build part.  My $.02. 

https://www.amazon.com/Rebuild-Your-Nissan-Datsun-Engine/dp/1931128030/ref=asc_df_1931128030/?tag=hyprod-20&linkCode=df0&hvadid=312014160183&hvpos=1o2&hvnetw=g&hvrand=4264106029397166523&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9012731&hvtargid=pla-684015945792&psc=1

[Zed Head]

Check the front cover carefully.  It has coolant on one side and oil on the other.  A crack or hole could cause your problem.

Also, check the thermostat housing and its bolts.  One of the bolt holes is a through-hole in to the cover, behind the chain guide.  Many timing chain guides have scars on the back side from using a too-long bolt in the T-stat housing.

 

[siteunseen]

Have you checked behind the water pump?  The front cover corrodes behind that little baby.

 

[madkaw]

If you are trying to find a coolant leak in the timing cover you need to pressurize the system. Go to Oriellys or Autozone and rent a coolant pressure tester . Put 15lbs on there or so and take the valve cover and listen. It will hiss if it’s pissing coolant . You might even be able to see it will a flashlight looking down the chain .

[youztheclue]

I already have the engine back down to the block in 21/2 hrs. its really easy after doing it the first time.

Edited August 24, 2019 by youztheclue