I'm changing a couple cylinders on a Continental O470R and noticed one of the hydraulic lifters was already bled down when I pulled the rocker cover. This was shortly after shutdown, maybe an hour or so. I'm assuming that would indicate the lifter is bad correct? Is it best to swap them out or do they tend to get debris around the check ball and just need cleaned? The engine has never cared for the cold until it has a decent amount of time too warm up so I was intentionally looking to see if the lifters were pumped up or not.

What are the usual signs of a collapsed lifter? Would it have an audible tick if it wasn't pumping up at all? Maybe higher EGT/CHTs depending on if its the exhaust or intake? Thanks

I had one on my IO-520. The CHT on that cylinder was slightly high but not concerning. Discovered it from an almost inaudible tapping during a run up without the cowl on. Only the guy outside could hear it. It took out the rocker and valve as well.

Doesn’t the lifter/cam follower come out the cylinder side on a 0-470? No need to split the case.
Pretty easy to pull the rocker and pushrod/PR tube, remove the spring clip then pull cam follower/lifter.
Check bleed down rate per SM.

Thanks for the feedback guys. Fortunately mine didn't cause any damage. I just found it odd that 11 of them were still pumped up and one wasn't. I missed the inspection of them in the manual, I assumed it would take some form of special tooling. The only thing it says for testing them is to remove the spring and put the plunger in dry, compress and release quickly and make sure it kicks back instantly. Ill have to play with mine a bit just out of curiosity.

Dogsbody wrote:Doesn’t the lifter/cam follower come out the cylinder side on a 0-470? No need to split the case.
Pretty easy to pull the rocker and pushrod/PR tube, remove the spring clip then pull cam follower/lifter.
Check bleed down rate per SM.

Correct, they do come out fairly easy. I pulled them while planning to do some cylinder work.... Long story short I think I'm going to bite the bullet and just do a full overhaul. More then likely a XP470 (Pponk)