Lycoming Wobble Test

Discussion on keeping your aircraft airworthy and legal and/or any technical topics.


Post Reply
User avatar
drak130
100+ Posts
Posts: 169
Joined: Mon Oct 21, 2019 7:59 am
Location: Angier, NC
Contact:

Lycoming Wobble Test

Post by drak130 »

Hello All,

Having Maule Flight do my first annual next week. My local A&P had suggested having a wobble test done. I talked to Kit last week and he said that they were not set up for that kind of check and he felt like it was not necessary on the older motors.

I just wanted to get some thoughts from the gallery. The motor is vintage 1998 Lycoming IO-540W1A5 and has 770 original hours. Before I brought it to the east coast it lived in Utah. The airplane flew an average of 20 hrs most years. So far I have put 70 hours on it since last March and I try to fly at least an hour a week. Thus far no issues (knock on wood). I do what has been suggested on this site regarding oil changes and analysis and fly 65% and 25 degrees LOP. I use 100W with camguard.

So what do people think? Wobble test worth it? Preventative maintenance or overkill? I'm also interest on peoples thoughts on boroscopes and frequency. II would have my local guy do those if the consensus swings that direction.

Thank you in advance

Hale-Yes
100+ Posts
Posts: 212
Joined: Sun Sep 06, 2015 7:32 pm
Location: Brawley, Ca. USA
Contact:

Re: Lycoming Wobble Test

Post by Hale-Yes »

My 2 cents is that I truly believe that changing oil often (every 25 hrs) or 4 months minimum is the key, and that doing routine oil analysis can give you an early warning of a building problem. Some will say that this schedule is excessive. I don't think so. Most aircraft engine breakdown (corrosion) is created by combustion gases mixing with and fouling the motor oil, in turn forming acid sledge that builds up in our oil and rusts our engines from the inside out. Compared to aircraft engine parts, oil is cheep.
"The problems we face today exist because the people who work for a living are out numbered by those who vote for a living" Author unknown.

Kirk
100+ Posts
Posts: 725
Joined: Tue Oct 17, 2006 3:07 pm
Location: KGCY
Contact:

Re: Lycoming Wobble Test

Post by Kirk »

I was in a similar situation when I bought my M5-235. Similar age and hours on the engine. I chose to run it and monitor its condition. Things worked out fine and 16 years later, it is now approaching TBO.

Not sure what you mean by “wobble test”. Checking valve play? We borescoped the cylinders, found significant pitting, good compressions. Oil consumption was somewhat high at 4 to 5 hours per quart and has not changed over the years. We felt acceptable and unchanging oil consumption and compressions was a good indicator of cylinder health.

Oil analysis was initially high in iron content as the rust wore off the pitting but settled down to normal levels after the first oil change. Again, we chose to monitor for acceptable levels with no change in trend. That’s the best indication of bottom end of engine health.

I did change the engine driven fuel pump the first year as a precaution against hardening of the diaphragm. We had found some fine black powder material in the fuel sump. Hardened or brittle seals are something to watch for, indicated by leaks or seeps.

You will run across many opinions. Personally, I believe monitoring engine health through borescoping, oil analysis and usage monitoring and feel of how the engine is running is a reasonable and safe practice.

Just my opinion. Good to listen to experienced mechanics and make a plan.

Kirk

Dale Smith
Posts: 81
Joined: Mon Feb 18, 2019 8:29 am
Location: NorCal
Contact:

Re: Lycoming Wobble Test

Post by Dale Smith »

Keep Flying the thing. Flying an hour a week like you are doing with help keep moisture out of the motor. I agree with oil changes often, fly it as much as possible. If you are doing oil analysis, see what the trend is doing. Keep in mind it will take a couple to see what is goin on. If you start noticing more oil consumption, drops in compressions, oil leaks, anything out of the normal, listen to what it is saying. Compressions are an interesting thing, we do leak down tests at 80psi. Cylinder pressures while running are in hundreds of PSI... I think most people will tell you that something is off when a motor heads south in a hurry. Human nature is to not want to believe it, not to mention the wallet will look the other way for a long time. Take care of the thing that you expect to take care of you, and listen to what it is saying!
No great story started with a good idea...

User avatar
gbarrier
100+ Posts
Posts: 1559
Joined: Thu Jul 14, 2011 5:41 pm
Location: 9NR4 North Carolina
Contact:

Re: Lycoming Wobble Test

Post by gbarrier »

If you want a wobble test, have your mechanic just push against the valve stems with his big old screwdriver. If he knows what he's doing he'll give you a TELAR (that looks about right) or not. Have seen my folks evaluate a lot of engine but never saw anyone use a jig.

User avatar
montana maule
100+ Posts
Posts: 308
Joined: Sun Sep 24, 2006 7:27 am
Contact:

Re: Lycoming Wobble Test

Post by montana maule »

I believe the reason Lycoming suggests the wobble test is to alleviate the problem of stuck valves. If they don't wobble enough, carbon is building up and may eventually cause the valve to stick in the guide. Of course too much wobble is a worn valve guide. Lycoming SB 388c. I have flown my O 540 just under 3000 hrs. and had two valves stick at the same time at about 850 hrs, of use. A common symptom to look for is a rough running engine at start up or first take off, then things smooth out. Things work OK when warm but after cooling down they tighten up. It doesn't get better by it's self and can cause pushrod bending and failure. That being said most people never check it and seldom have a problem.

Post Reply

Who is online

Users browsing this forum: No registered users and 15 guests