Season's greetings!
I'm currently doing a cooling system overhaul and figured I'd do some small things here and there while I have room. 1999 sport 2wd 4.0, 190k on the clock.
First question:
On the radiator, is there supposed to be an o-ring where the high pressure transmission line disconnect is? When I pulled the line using the fuel line tool there was nothing there but I feel there should be one...
Next, I'm doing the valve cover gasket for the 2nd time in 4 years and while inspecting my valvetrain I noticed some sludge on the 1st and 3rd rods from the firewall. Is this something I should/can address while the cover is off? I've included pics to show the sludge. I've been using Castrol GTX high mileage 10w-30 synthetic blend. Oil changed every 4000-4500 miles. California daily driver. Any and all advice is appreciated!

 

I've changed out a few radiators & I don't recall ever seeing any O-rings involved. They would have to be made of something that can stand serious heat if they did exist.

The sludge; doesn't look too serious. You should be able to get most of it off. You might as well list the oil brand & weight you are using. Everyone is going to ask.