The International Cessna^® 170 Association

Hi folks,

I've been away from the forum for a while. Thought I'd share my recent experience that will, unfortunately, have my 170 grounded for a long while.

After getting home from Oshkosh last month, I started an oil change that very evening. I was utterly shocked to find my oil screen was covered in metal! Long story short, the ring land of #1 cylinder was nearly disintegrated (yet the rings were all intact). Metal in all the bearings, engine is now completely disassembled for an early, and unbudgeted overhaul

That particular cylinder and piston were an exchanged overhaul assembly 173 hrs ago. The previous oil change 28 hrs prior showed only a few specs of metal, well within the general "ok" criteria. The only thing I had noticed in operation was that oil consumption had been increasing rather sharply. Spark plugs looked normal, but compression was down to 30/80 for that cylinder.

As a side note, after removing all the cylinders for disassembly, I also found that the #6 piston has a crack in the center of the skirt that extends all the way through the bottom ring . That was a problem that hadn't shown up yet, but surely would have! It was also an exchanged O/H unit.

I think I'm through with overhauled cylinder assemblies. You just don't know how many hours any of the components have unless you have the means to track them from new.

Also, I'll be installing an oil filter system when this is all over, as it certainly can only help. With the amount of metal that ended up in my pan, however, I doubt that any filter system could have prevented this repair, only reduced the amount of damage.

I posted this pic of the oil screen on the 170 Facebook site when it happened. It turned into a real shouting match over the merits of filters and oil analysis. Social media... Go figure.

(more pics)

Sorry for your expensive oil change. On the good side, the piston didn't disintegrate in flight. That could have been a lot more expensive. Hope you are back in the air soon.

Looking and the cracked piston it almost looks like someone tried to weld it.

Aren't you glad you do regular oil changes? That amount of metal surely indicates a serious problem but since you did the recommended oil change it was caught in one cycle. The old Continental brought you home safely as it was giving you very good hints all was not right. Had you ignored the conditions your plane might not be in one piece safely at the airport. I would say you are very fortunate that you used good judgement.

Yes the exchange units are not that cheap in the long run , it's getting to the point now that it's more prudent to fit brand new assemblies and not overhauling your own cylinder assemblies . I am amazed when you go on to flea bay and see what people are trying to sell . It only makes good scrap metal and not to be fitted to aircraft .

My condolences on your untimely overhaul. The longer you stay in this aircraft ownership arena, you will eventually get to experience the trials and tribulations once or even twice. Glad you didnt just take the recommendations that were made to you on facebook and you choose to tear it down. That A&P that recommended the teardown is a keeper. Doug

"overhaul" and "exchange" cyl assy's are not anything we should be using these days. They are not cost-effective compared to new units if you're going to keep the plane. (especially when compared to the labor costs and down-time which are identical.)
And you are correct.... you have no idea what/where/how-much you're really getting....

I won't disagree that there are definitely several silver linings around this dark cloud. As was said, we were able to make the 8hr round trip to Oshkosh without incident, including time over the busy Chicago/Lake Michigan shoreline where an emergency landing would have been difficult to say the least.

Some of you may recall the incident I had with this same engine a few years ago when we cracked a cylinder around the barrel in flight. That too was a case of an overhauled cylinder failing by fatigue.

In both cases, the engine continued to run smoothly making good power throughout, even while catastrophe was going on inside.

As for my current situation, I actually purchased a spare, lower time, disassembled engine last year with the idea that we could O/H it by field method on the side and have it ready to swap whenever the time came... I just didn't realize that time would be less than 12 months away! So that time table has been accelerated, but is slow-going. I'll keep you all posted on the progress. I'm hoping to be back in the air before winter.

In the mean time, I've started renting again, which is a tough pill to swallow after being an owner for the last several years.

-Kennet

In my opionion, no metal in the screen is acceptable, i personally would have grounded it on the spot, if i had been your, I.A. ,and inspected the problem further,im sorry you had this expensive problem, but thank goodness, it didn,t come apart over
heavy bush country, or a body of water ,good find,your able to rebuild her, and keep flying, the main thing here you were not hurt ,great work on finding the problem, and looking after it,i know how it feels to come down, after a catistrafic engine
failure, 1st in a Taylorcraft model 19 Years ago, and 2nd time 7 yrs ago in a PA11 Cub each time i was very lucky i was able to put both planes down in a reasonable area and didnt damage eighter Aircraft ,im glad your safe, and sound, we need all our Pilot,friends, have a great day sir im in my 70s now but hope to fly my Planes for a few more years,this is a great club we belong to.

Paul.