Hello all,new here,hope I'm in the right area?
have a question on which way my hydraulic chain tensioner metal "o-ring" seals go. They have a slight dome shape when looked at sideways. I thought they were flat,but no and i've heard that it DOES matter which way they face, haven't taken orig ones out yet and prob wont be able to tell since they probably flatten after torqued down.
I have 138k on well serviced engine,had it since new and am finding out that those tensioners s/b changed every 75- 100k to avoid damaging guides/ cassetttes, doe anyone have correct info on which way those little ford oem washers go? Thanks ahead of time. sm

 

The dome is in cross section? This is the first I've heard of it.

 

That's the best way I can describe,when looked at from cross section....thin side on,these factory motorcraft seals that are VERY thin spring type steel with a black coating on them,have a definite arch to them,but looking at the motorcraft oem tensioner,they are not tapered ( like a peanut spark plug), tensioner where it contacts head is flat....weird uh?
Google "which way to install ford 4.0l sohc v6 engine tensioner metal o-ring seal" and see what you make of it,which side is the flat side since seal ring has the arch in it.

 

Found out when down at local stealership today,old guy who has done a few says it doesn't matter which way really,since seat area is flat,but he installs cup or arch facing out away from head,New o- ring factory torque spec 32 ft lbs,plus maybe a few more to make sure,and said NEVER use antiseize OR rtv,since it will affect torque spec and not needed if sealing surface is clean and nick or burr free.