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Old 09-26-2018, 01:10 PM
rotoiti's Avatar
rotoiti rotoiti is offline
Join Date: Jan 2013
Location: Bay Area, CA
Posts: 168

Yes, I tried running it with 9 quarts, 8, 7 and 6 quarts respectively for about 10 hour periods each. The consumption was pretty much the same. I never flew with more than 10 qts.

Re: mechanic. He's a good guy, A&P with IA who has been working on my airplane for 4 years since I bought it. He is convinced magnetos are more reliable than electronic ignition. If you have a recommendation around SF Bay Area for a mechanic familiar with IO-540 and not afraid of working on "experimentals", then I am all ears. As I said, I want to get a second opinion.
Llama (RV-10), flying, 450 hours.
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Old 09-26-2018, 07:21 PM
F1R F1R is offline
Join Date: Nov 2010
Location: ____
Posts: 736
Default I second his opinion

Just my opinion, but I agree with your current mechanic about running mags on a 540.

It would be unwise to force a technology foreign to the dentist you have a relationship with that is actually working inside your mouth....

Some people have great reports with various EI systems. I am not one of them. In the mountains and over water I will carry on with mags.

A good A&P friend has an R22 with an O 360 about 200 hours since a pro shop did a 2000 hour on a first run engine. His compressions are 78/80 and better. 2 of the cylinders are 80/80. He still has an abnormal high oil consumption. Higher than before it went for rebuild. I suspect the valve guides are responsible in his case.

Do you have a plain breather system? or a positive evacuation (suction) system for a breather?

Tom Martin did some manometer pressure testing of the exit cowl of Rockets. He found that about 2" aft of the bottom edge of the fibreglass cowl exit, was the lowest pressure. That is where he positioned his breather tube exit. If your rings are OK.. and IFF the oil is going between the valve stems and guides , having some negative pressure in the crankcase might help... but perhaps tough to overcome the suction in the intake tubes and ports where the valve guides terminate.

Perhaps check the oil return lines are good and clear from the rocker boxes. It would only take 1 out of 6 to be restricted or blocked and the consumption would go up.

Last edited by F1R : 09-26-2018 at 07:54 PM.
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Old 10-04-2018, 11:25 AM
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rotoiti rotoiti is offline
Join Date: Jan 2013
Location: Bay Area, CA
Posts: 168

This engine has a regular breather.

I have talked with the mechanic and raised the concern again. He is going to check the valve guides. He is also going to look at the piston heads for discoloration with borescope. I will update this thread when I know more.
Llama (RV-10), flying, 450 hours.
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Old 10-04-2018, 04:16 PM
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sglynn sglynn is offline
Join Date: Mar 2008
Location: Anacortes, WA
Posts: 773
Default oil consumption

My O-540 got a new engine a few years ago. It only uses 1-2 QTs per 25 hour.
I was careful to do the break in with no wasted idle time. I think break-in is really important to get those rings burned into the cylinder walls. The first hour is especially important for the ring burn in. I did first 10 hours of breakin with 100% mineral oil by Phillips 100 weight. Then I ran 20W-50 Phillips XC which has no additives so I also add one bottle of CamGuard.

Your high oil consumption sounds like a good break in didn't happen after the top end. Perhaps the owner then didn't know a top-end overhaul needs a break in just like an all new or rebuilt.

I second the idea of getting second opinion from another A&P/AI. You are probably close to a major overhaul.
Steve Lynn
Flying Phase I
Anacortes, WA
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Old 10-04-2018, 07:59 PM
andyrv andyrv is offline
Join Date: Feb 2005
Location: Leawood, KS
Posts: 272
Default Hours between oil changes

How many hours are you going between oil and filter changes?

Andy Cobb
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Old 10-11-2018, 01:17 PM
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rotoiti rotoiti is offline
Join Date: Jan 2013
Location: Bay Area, CA
Posts: 168

I change oil every 25 hours.

I just dropped the airplane at the shop. They did a compression check and apparently cylinders 2, 4 and 6 have compression values in high 40s :-O During annual in June, they had 67-70. I am highly surprised.
Llama (RV-10), flying, 450 hours.
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Old 10-11-2018, 02:00 PM
bobnoffs bobnoffs is offline
Join Date: Jul 2012
Location: n. wi
Posts: 606

same shop for both checks?
Bob Noffs
n. wi.
dakota hawk/jab 3300 built and flying. sold 6/18.getting serious about the 12.
RV-12 kit as of 9/13
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Old 10-11-2018, 02:06 PM
lr172 lr172 is offline
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 4,022

Originally Posted by rotoiti View Post
I change oil every 25 hours.

I just dropped the airplane at the shop. They did a compression check and apparently cylinders 2, 4 and 6 have compression values in high 40s :-O During annual in June, they had 67-70. I am highly surprised.
While it is unfortunate for you, it is a good lesson for others. Don't ignore it when your engine is talking to you. relatively rapid increases in oil consumption means that something is happening and it usually isn't good.

Please let us know the final diagnosis.

I also would look for another mechanic. First, he should have been concerned with the significant increase in oil consumption. Second, 1 qt in 1.5 hours is a strong indicator for pulling a couple jugs to see what is going on. Advising you to ignore the symptoms and just throw more oil at it, is bad advise in my opinion. The cause may be something that you can ignore and address with oil and it may not. However, not knowing the cause means you are taking unnecessary risk.

RV-6A / IO-320, Flying as of 8/2015
RV-10 in progress

Last edited by lr172 : 10-11-2018 at 02:11 PM.
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Old 10-11-2018, 04:02 PM
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PerfTech PerfTech is offline
Join Date: Sep 2010
Location: Redlands, Ca.
Posts: 1,370
Default Food for thought!

Ö We build, modify and test a lot of engines at our facility, and thought our
testing procedures could be of interest to some reading this thread. The leak
down test, that is commonly referred to as a compression test in the aviation
community, really doesn't provide much of the true picture of cylinder health.
Firstly it only addresses what is happening at the very top of the stroke, and
then only the compression ring. Its very possible that one or two inches down
the bore a completely different scenario exists. Cylinder taper, galling, pin
button damage Etc. can be happening and the leak down numbers can be
perfect. After performing the standard test, while the top plugs are out get an
automotive type compression tester and do a cranking compression test as well.
This will or can expose some possible other problems, and you can't have
too much information. High oil consumption can many times be attributed
to a stuck or broken oil ring or wiper ring, that will not show up on either of
the compression tests. Always do a cranking test as well. It only takes a couple
of minutes and can provide considerably more information. Thanks, Allan...
Allan Nimmo
Innovative Aircraft Safety
Products, Tools & Services
Southern California (KREI)
RV-9A / Edge-540
(909) 824-1020
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Old 10-12-2018, 08:59 AM
tim2542 tim2542 is offline
Join Date: Aug 2009
Location: Redding,Ca
Posts: 633

A good borescope, spark plug and ex pipe inspection along with leakdown and Allenís suggested compression test may indicate only 1 or 2 cylinders need to be pulled. Glazed cylinders is seen as brown patches on the cyl walls.
If its only 3.5 hrs/qt. and all other tests are negative it will be hard to know whether to run it or do surgery. Certainly increasing oil usage is indicator to pay attention to.
Good luck
Tim Andres
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