Below is a video of replacing the valve seals on a 24 valve cummins engine.
first get a valve compression tool that is for the 24v head.
remove injector hold down bolt
bolt base of tool to the injector hold down bolt holes snug is fine
place top of tool on springs centering over valve stems
with the greased nut, tighten tool down until all the valve stem keepers are retrievable
many times the valve seat will stick to the keepers and will need to be broken loose with a socket and hammer to free them (see in video)
pull keepers keys (2 halves) with a magnet and place on a template for each valve (do not mix any parts to other valves)
loosen tool and remove plate
take springs and keeper seats off and place in there designated holder
with pliers, grip and twist and pull the old seals off
clean seal seats as there will be crud under them from oil and soot
yellow seals are intake14mm deepwell socket to drive these
green seals are exhaust 13mm deepwell socket to drive these
replace yellow for yellow and green for green after cleaning seal seats on head
place each spring and keeper seats back to original positions and ensure they are seated in the head properly (not sitting on a machined lip)
then pull on each valve stem to make sure they are all the way up
place tool plate back on and centered
place nut back on the tool and torque down to where you are able to place the keepers back in
once keepers are put into the "keeper pocket" push the valve down a little to get the keepers to grab the valve stem (may need to elevate the head a bit to get clearance to do this)
when all keepers are preset, untorque the tool and watch the springs to ensure they grab the keepers and they sit in the pocket properly
when pressure is off remove top of tool and remove bottom of tool
re-install injector hold down bolt with a dab of BLUE loctite
inspect all 4 valves for proper re-installation
done
if valves are to be replaced or different springs are to be replaced it is the same steps outlined above. for more details please watch video below.