Detergent oil

[SeaSlugs]

Originally Posted by 40 Deluxe

Didn't know there are seals in hydraulic lifters!

thats what make them hydraulic - tappets or solid lifters are just that. no cushioning effect and thus must adjust valves and worry about zinc levels in modern engines (jeeps 4.0 straight 6 for example)

https://www.youtube.com/watch?v=lorANZ1Tptw

crude but shows how a hyd lifter works - some have seals some are extreme tight machining processes that act as a seal but wear increases the gap with time so as oil heats up it sounds like box o rocks cuz no pressure. but yes they can get stuck (generally from too much wear and parts bind) but from what ive seen and experienced they usually are worn out/leaky.