Coolant leaking from drivers side head

[sidneyhop]

1998 4.0 SOHC

I posted a thread earlier but now have more information relating to my problem and some additional random pics of the location. Ive sprung a leak in the rear of my drivers side head. It looks like its coming from a type of freeze plug but the size is about 1/8" smaller than the 1 1/2" ones the guy at NAPA said went into the heads. The area where its coming from also looks like its a port where something could be bracketed onto put is just plugged. Any idea what this is for and the size of plug thats supposed to go there? Thanks in advance.

 

[sidneyhop]

**Update**

I was able to fix the leak using a 34 - 38 mm rubber expansion plug. The one that failed was badly corroded and I initially was going to put in a brass replacement put the awkward angle made it nearly impossible to tap into place without removing the intake and head itself. The rubber one went in with just a little wrangling and I didnt have to remove anything too big to do it. Hope this helps if anyone encounters the same problem.