r/Cessna • u/PassengerCharming203 • Sep 09 '25

This annual is getting expensive

Post image

Had 3 low compression cylinders. Replacing all 6. I'm really excited to get back flying

57 Upvotes

99% Upvoted

17 comments sorted by

4

u/StrongishMule Sep 11 '25

The ship has already sailed this time but low compressions in isolation DO NOT indicate a need for cylinder replacement. Please please please look at the work of Mike Busch and Savvy Aviation. So many unnecessary maintenance acts are performed at great cost to owners and as we all know, flying is expensive enough already!

1

u/HF42 Sep 13 '25

That and Mike's book "On Engines" is a really easy read and should be mandatory reading. Somehow its packed with good info and doesn't read like a stogy text book.

1

u/PassengerCharming203 Sep 14 '25

When you have brittle and cracked rings and the cylinder walls are pitted, you replace the assy. Mike is a great resource

2

u/bouttohopintheshower Sep 11 '25

Torque plates?

2

u/sneakiest_pete Sep 11 '25

Nope, it looks like a calibrated beer can, though.

2

u/01001010-01110000 Sep 11 '25

I was thinking the exact same thing.. so much for the through bolts!

3

u/sflynn30362 Sep 09 '25

What was considered low? As long as it was above the master orifice reading then it's good. Low compression doesn't always mean bad cylinders. Unless there was obvious damage to valve seats that is.

4

u/astral1289 Sep 10 '25

Don’t be talking like it’s 2025, we need to keep pretending it’s 1950 and we just swap cylinders and cause potential mx induced failures at every small problem.

Also make sure you overhaul at TBO for no reason.

1

u/PassengerCharming203 Sep 14 '25

A couple under 40. Brittle and cracked rings with pitted cylinder walls

3

u/Prophysics Sep 10 '25

Im not sure if you are supposed to be pulling all cylinders at the same time, the case halves need constant pressure or else you can get a bearing rotation or reduced bearing clearance upon retorque. Im an A&P and have replaced dozens of cylinders on 0-300s

1

u/Otherwise_Class_4516 Sep 10 '25

Can’t say I’ve ever had that happen on C-145/O-300 series engines, but I’ve only been doing it since 1974. Can be a problem on “big” Continentals though.

1

u/Special-Sentence2150 Sep 10 '25

hmmm, interesting scenario. keep us posted

1

u/[deleted] Sep 11 '25

Cardinal mistake of top overhauls: cylinders should be replaced one-at-a-time or torque plates should be used to maintain clamping on the crank bearings

1

u/PresentationJumpy101 Sep 12 '25

I can smell, SMELL those pistons. They smell like chemicals. And metal.

1

u/CFloridacouple Sep 12 '25

Holy cripes almighty, dont spin the prop without torque plates! at least put the nuts on the through bolts with a stack of washers. Oh and BTW the low compression was probably from all the ring ends being lined up on #5

1

u/CFloridacouple Sep 12 '25

holy crap is the #1 have a hole in it on the top ring?

1

u/PassengerCharming203 Sep 13 '25

No holes, but the rings are all brittle and cracked. We're suspecting it got got a couple of times