CC340 Engine Oil Consumption Issues

[stede52]

I’ve had an oil consumption issue in my 2015 CC340 engine (engine built/assembled in 2014 by Aero Sport) for some time now and just recently found out what the issue is but I’m trying to figure out WHY at 750hrs on the engine! First, just a bit of background on my engine; I’ve never had a heat problem with my CHTs or EGTs nor have I ever had the need to fly CHT’s above 400 degrees. A typical flight in cruise for me at 2200-2450 rpms has my CHT’s between 350-375, EGTs 1300-1350, oil 180-190. I have the standard 25-degree timing ring and normally cruise 50-100 degrees ROP. I just recently did a hot leak down test before my Idaho trip and it was good (74/80, 76/80, 80/80 and 79/80).

Now the problems: The engine started out pretty normal after break-in and then at about 300 hrs I started noticing the oil consumption going up from 1qt per 10-12hrs to 1qt every 6-8hrs and then to 1 qt every 4-6 hrs in the first quarter of 2019. During this time frame the oil reports continued to show slight increases of lead, which I didn't think much of at the time. I also noticed that the residue on the landing gear started tuning a dark brown rather than the light grey it had been. This continued to get darker until a compression ring broke on my way back from Utah in May 2019. After getting that problem fixed I thought the oil consumption would go back to 10-12/qt rate but it didn’t, It continued at to get worse and just recently during a trip to Idaho I was burning 1 qt every 3 hours with 750hrs on the engine.

The bore-scope on cylinders 1,2 and 4 showed a considerable amount of oil was getting thru the rings, #3 which I rebuilt 1 year ago was good. After removing a the jugs it was very apparent the rings were completely worn out on 1,2 and 4, this had obviously been going on for some time. Aero Sport now has all the jugs and they are also baffled why the rings failed so soon. Possibly the wrong rings for these kind of cylinders or a bad batch of rings (whatever that means?????). The other issue I’m having is pitting on the valves and pistons. 3 exhaust and 3 intake valves need to be replaced, however, all the valve guides and cylinder walls are good. I fly about 150hr a year and have never pulled any water out of the tanks so corrosion seems unlikely and this kind of pitting was not due to detonation. Again baffling.

My question to everyone is: has anyone else had this kind of ring wear/problems this early in the life of their engine, especially ones built on the 2014-15 time frame? This was also the time frame in which Continental was purchasing ECI Titan.

DSCN0100.jpgDSCN0099.jpgCyl#4-6.jpgCyl#2-6.jpgCyl#1-15.jpg

[Dan L]

Steve, you are having some problems. Two questions come to mind right off; what oil are you using and are you burning 100LL?

I am surprised that Your compressions were as good as they were with bad rings.

My O340 was built in 2010 and I have a similar oil useage. I now use about a quart in 6 hours or so. I have a Vetterman exhaust system and the Engine breather doesn’t drain into the Exhaust collector. When I put a pod on in 2017 the oil consumption went up and the front of the pod was always oily. It seemed as the pod changed the air flow in the cabana area and was encouraging oil to come out the breather easier. I made a few changes and experiments on the breather exit and that has helped.

I use Phillips XC oil with CamGuard.

[stede52]

Dan, I'm using 100LL and Aeroshell W100 (summer time) w/camguard, (recommended by Aero Sport)

I've been told by a number of mechanics that the leak down looks good because: 1. the engine is hot, 2. the excess oil will seal the rings in many cases. We measured the gap on one of the compression rings for #2 and the gap was .040 over rejection spec, hard to believe the oil could seal that kind of gap, but we tried it 2-3 times on each cylinder.

The strange thing is that I have never had really oily plugs, (however they were dark brown/black), just a little shinny on #2 this time, or any oil on the bottom of the plane only black soot on the gear cabane area so it doing a good job of burning all that oil. I also took off the breath and put it into a bottle and found that after 8 hours of flying there was only a couple tablespoon or so of oil in the bottle, so it wasn't getting sucked out of the breather.

Here's pics of the excess oil on the cylinder walls of 1,2&4.

[aeroaddict]

Just curious, what oil level do you try to maintain?

[stede52]

Just curious, what oil level do you try to maintain?

between 4.5 and 5

[40m]

Just curious, what oil level do you try to maintain?

EX2 on 31" Bushwheels

At oil and filter change.
5qts it shows 4.5 on stick before running engine.
After running for leak check and letting it sit overnight oil on stick shows 4qts.
Mine will require 1/2 qt. after 6-7 hours which is when I put it back in.
Side note Aero Sport told me 5qt min.
Aeroshell 100P

[aeroaddict]

Same here; between 4 1/2 to 5 qts. Oil wise I use Phillips

[stede52]

EX2 on 31" Bushwheels

At oil and filter change.
5qts it shows 4.5 on stick before running engine.
After running for leak check and letting it sit overnight oil on stick shows 4qts.
Mine will require 1/2 qt. after 6-7 hours which is when I put it back in.
Side note Aero Sport told me 5qt min.
Aeroshell 100P

You have the same route as I do and Aero Sport told me the same thing, try to keep it at 5 quarts

The good news from Aero Sport yesterday, was that I should see my parts back by the end of next week

[40m]

You have the same route as I do and Aero Sport told me the same thing, try to keep it at 5 quarts

The good news from Aero Sport yesterday, was that I should see my parts back by the end of next week

Steve,
Glad for you and the parts. I am curious about your general flying conditions, rpm ranges, leaning habits and others which I can compare to.
Starting off we at least know our oil temps are correct thanks to your help.

Thanks, VT Glenn

[aeroaddict]

I'll second the oil temps! The oil cooler door works perfect!!! Could never get the temps up, but then again, flew the Phase I off over winter.

Any idea on the root cause yet? I lean ROP with similar cruse temps as yours.