Hi. I am remedying numerous oil leaks on my daughters 2005 Civic LX D17A1 auto transmission sedan. The vehicle overheated twice recently and so I wanted to pull the head to see if it had warped. When I had the head off and blew out the head bolt holes I found a small black o ring laying on one of the rags I put in the cylinders. It is not the oil restrictor o ring as I have that. I have searched all over the web, looked at every parts manual available on line and nowhere is there a sign of this O ring. It measures 0.375” OD, approx 9.5mm. It has to have come from somewhere on the head/valve train. I did take out the rocker shafts before before lifting out the head. I have looked at every hole in the rocker shaft assembly and the block and see nowhere an O ring will fit. It seemed to appear after I blew out the block head bolt holes. I would really appreciate it if anyone can enlighten me as to where it might have come from.
Thanks Bill

 

If you planed the head, find 10 hardened machine washers and put one under each head bolt.
The head bolts are very close to bottoming in the block and can do so.
The washers insure there is sufficient clamping force on the head and gasket before the bolts bottom in the block.

 

Thanks for the heads up on that. Head is at the shop but hopefully only a polish. I will do a depth measurement when it is back. Still hunting the oil orifice o ring issue.
Thanks again.