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Darren S

Well Known Member
I have a Superior IO-360, 340 hours on it. First run in 2006. Previous annuals the cylinders were : 77, 78, 78, 75. Pretty good. Today my guy told me that all cylinders were mid 70's but #3 was 50 !!! Yea 50.

He said the plugs were in good shape and he didn't suspect the rings, but that perhaps a chunk of carbon maybe stuck on the valve preventing it from seating.

I lean on idle and taxing, lean during flight, run 65% power pretty much all the time. Change oil every 30-45 hours. He said that #4 bottom plug has some good sized carbon chunks.

So..... do any of you engine guru's have an idea to remove the potential carbon chunk from #3 ?

The compression check was done cold not after engine warm up. I asked him to check it again tomorrow after the engine is warm. I am praying there is a difference. Am I looking at having someone take the head off/overhaul ?

This sucks as I fly regularly and have done all I can to prevent a top overhaul.

I'm kind of bummed. I treat the engine as best I can and then this happens.

Thanks in advance for any suggestions.

Darren
 
It is not uncommon for this to happen. Run the engine 3-4 hours and retest the compression. This has happened twice to me over the yesrs. Both times were false alarms and the second reading was fine.
 
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Darren S said:
So..... do any of you engine guru's have an idea to remove the potential carbon chunk from #3 ?
Click to expand...

Like Larry mentioned, run it.

I did my condition inspection and compression check last month; I did a short ground run to warm it up before pulling the plugs and hooking up the air hose... 3 jugs were fine, but #3 read roughly 5 psi and I could hear/feel air coming out the exhaust pipe. Oops. I took it back out, ran it for 10 minutes or so including a mag check and prop cycles, then checked #3 again. All was well, 75/80. Top overhaul averted.
 
You guys have given me hope !!!!!!!!!!!! Thanks for the advice. What do you guys think was the reason for the low readings ?

The engine was cold so things weren't sealed up as well ? You weren't at TDC at first ? Was it a carbon chunk preventing the seating of the valve ?

Either way I am surely going to warm it up good and get my guy to check it again.

Fingers crossed, prayers said :)

Darren
 
what about lead.........

issues instead of carbon? when the plugs are out look inside just past the threads and see if there is any lead buildup. how about a look inside with a borescope? if it is lead you can use TCP to help out. hopefully is just a bit of carbon but i would want to know. here is a pic of what i was talking about. good luck.
img1229g.jpg
 
Crack

Ok this sounds like what I just went through. I had no idea as it was running perfect so I assumed it was carbon too, NOPE. Cracked cylinder, I had to buy a new one and then have it bored to match the other cylinders.

Mike
 
Something similar happened to me recently. Fairly new O-360 from Bart, about 150 hours on it, Lycoming cylinders. Last condition inspection, #2 cylinder was 60/80. Ran the engine, re-checked it, same. A couple of months later, checked it again, same. I spoke to a local engine guy who suggested boroscoping to check for carbon under a valve and possibly "staking" the valve (basically banging on the valve to try to loosen the carbon).

I spoke to Bart and he said "send me all four cylinders and I'll check them." Seemed like overkill to me, but I did take him up on his offer and sent him the #2 cylinder while I was doing this year's condition inspection. He turned it around in a couple of days, so total down time was just under 2 weeks. Bart re-ringed the piston, ground the valve/seats, honed the cylinder, etc., no charge of course, and he paid the shipping back. Bart is great about this! Bart said he could find nothing wrong, but we suspect a bad ring (I had pulled the rings before I shipped the cylinder to him). So I'm running mineral oil again for the next 25 hours, so far so good! :)

Not sure I'll ever know what happened for sure.

[Oh yeah, Paul's post below reminded me and I forgot to mention that air was escaping out the breather, so this, too, would indicate a ring problem.]
 
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I am afraid I have never understood mechanics who want to pronounce a problem after doing a COLD compression check. Yeah, it's easier to do the compression check when the engine isn't going to burn your hands, but the purpose is to get a good compression check, not make it easier to do the test. I agree with everyone here - run it, then check again - most likely, the "problem" goes away. The other thing your mechanic should have done was tell you where the air was escaping - listen to three places - the inlet, exhaust pipe, and oil dipstick tube - this will tell you if you have air coming out the Intake valve, Exhaust valve, or past the rings.

If it's a valve, stake the valve then try again. Lots to try before you pull that jug!

Paul
 
Darren S said:
You guys have given me hope !!!!!!!!!!!! Thanks for the advice. What do you guys think was the reason for the low readings ?

The engine was cold so things weren't sealed up as well ? You weren't at TDC at first ? Was it a carbon chunk preventing the seating of the valve ?

Either way I am surely going to warm it up good and get my guy to check it again.

Fingers crossed, prayers said :)

Darren
Click to expand...

Could be any of the things you mentioned, all it takes is one.
 
I am going thru something similar, and just want to point out one more thing to check...I had #4 come up 62/80 warm a couple months ago. Freaked me out...I had our guys look at it (I work at an FBO), and after scoping it, finding no carbon, we decided to pull the hydraulic lifters. Found one of them had some "junk" in it, preventing the exhaust valve from fully seating. We did another compression (yes, cold this time as the airplane and engine were no where near ready to run at this point), and it came up to 68/80 cold. I haven't checked it warm yet, but I have flown it 7 hours since then, and will check it soon...have to pull the cowl to finish my smoke system. ;)

So...I can suggest checking the lifters...:cool:
 
I am afraid I have never understood mechanics who want to pronounce a problem after doing a COLD compression check. Yeah, it's easier to do the compression check when the engine isn't going to burn your hands, but the purpose is to get a good compression check, not make it easier to do the test.
Click to expand...

Paul, after only 30+ years of doing compression checks this is what I've learned: A good jug is a good jug. Hot, cold, don' matter. Sure they'll often read better hot, big deal. If they don't check pretty good cold, there's something wrong inside. Not always broken, but something wrong. A good jug will only gain a couple pounds hot vs. cold. Many times carbon or lead is the culprit, but often this is just an assumption reinforced by a false fix. Typically someone will stake the valves on a leaker and get a better seal. Then they'll blame it on carbon/lead when in reality what they've done is just knock a poor fitting valve face into it's sweet spot. Voila, she is fix! Not so. People argue that all the parts don't fit right if you're not at operating temperature. Not correct. Maybe true, but not correct. They fit cold when they were new, why not now? Also, many ring problems are masked by excessive oil in the jug. Many oil pumpers will show mid-seventies on compression only because the rings are coked & oily. Were you to clean the rings & cylinder walls you'd find that it actually sucks. So, checking hot really only helps to fine tune a trend analysis. Even then there is a lot of variability between compression checks because rings move around even if the valves are perfect, which they often aren't. Summary: Good is good, bad is bad, and it's not that big a deal to rip off a jug & fix one. That's one big advantage of an opposed engine with bolt-on jugs, easy to fix.
 
Aerhed,

I really don't disagree with you - a truly bad jug is going to point itself out either way. I get annoyed when you find one that is marginal, kind of on the edge, and the mechanic goes "if it were just a couple psi better, I'd pass it..." Well, you can get a couple of psi between hot and cold. But all the really bad jugs I've seen could be found by just pulling the prop through - the bad ones are noticeable by feel. But like you said, if you want to do consistent trend analysis, doing it the same way every time is important. You probably know a bad jug is bad before you pull out the compression tester.

Paul
 
"Poor man's" compression test

My engine has consistently (for 1250+ hours) had compressions about 78,78,76,72. Each annual is more or less those numbers. I have always been able to hear air blowing by the rings on #4 if I listen in the oil fill hole.

Even with the lowest being as high as 72, if I pull the prop through four cycles, I can tell you which one is #4. If you (check ignition!) pull your prop through, and one is really at 50, it will REALLY be noticeable. I'd fly it and pull the prop through after the next several flights, and see what you feel. If something really did change, you'll feel the soft cylinder and can investigate further.
 
Iv had a similar issue and found that air was leaking into exhaust stack, what we found was a sticky valve. We drop the valve, honed it out and put it back in service, flys fine and compression is fine..
 
Good Info

I also make it a habit to do the poor man's comp test prior to each flight. I also have one cylinder that seems a bit softer than the others.

It seems that if I go back and check it the second time, it seems "up to snuff".

IO 360 with chrome cylinders that runs great but burns a bit more oil than I'd like (1 qt per 15 hours).

Normally have my A/P do the comp check at condition check, but I'll do the next one and pay closer attention after reading this good info. Thanks

Fair winds
 
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Ok, I just wanted to update my original post. I spent a good half day at the airport with the fella doing my engine work.

From my reading last night, talking to some people and the responses to this post, I figured my first chore was to "Stake" the valve and then check the compression again. Run the engine, warm it up and check it again.

So we took off the rocker cover of #3, got a block of wood and gave the rocker arm of the intake and exhaust valves a good couple of whacks !! Very scientific :)

BTW, the air leak was from the intake valve as you could hear air leaking from the inlet.

Check of the compression yielded a compression of 68/80 !! Big jump from 50/80. So next we ran the engine, warmed it up and the compression came up to 75/80 !! I was all smiles.

There were some decent sized lead chunks on the plugs of #3 and #4. So I pose the question of, "What can I do to help prevent lead build up on the valve faces ?"

As stated earlier, I lean at idle, lean at taxi, lean in my run up, lean in flight. In cruise I lean to peak and then run 25 - 40* ROP. Evidently #3 is the cylinder that peaks first.

So thanks to all for chiming in and tell me what you do to help prevent lead deposits, or is it inevitable?

Darren
 
Dang Jeff !! Thanks for the link. Never heard of the stuff but will certainly give it a go. This lead build up issue gave me a scare.

Any negatives with using TCP ?

Will it help to clear out existing lead ? ie. use a slightly higher dose (1 oz./gallon) for a few tanks and then go to a maintenance dose (1/2 oz./gallon)

Thanks again,

Darren
 
Avblend and MMO have seemed to help my C 85 that stuck the #3 valve 18 hrs after I got the plane. We rope tricked it then 20 hrs later same valve hung. Started Avblend and MMO [Marvel Mystery Oil], yes I know its mineral spirits and wintergreen, but 249 hrs later the rope has'nt been back in that cyl or any other YMMV.
 
I just ordered some TCP from Decalin chemicals and will start using it as soon as it arrives.

If I fly 25* LOP, will that help clear out any existing carbon build up in my engine? Or is it stuck there once it forms ?

I know there are a bunch of opinions on LOP vs. ROP and I have read the articles by Deakin. I did try LOP flying for a bit but was staring at the darn EFIS so much and not out the windshield, I was afraid I was going to fly into something:)

I have learned that at 65% power, which is where I fly mostly, there is very little I can do, as far as leaning, that will hurt the engine. So I am willing to lean out things a bit more if it will cut down on carbon build up

opinions ?

Darren
 
Darren S said:
I have learned that at 65% power, which is where I fly mostly, there is very little I can do, as far as leaning, that will hurt the engine. So I am willing to lean out things a bit more if it will cut down on carbon build up

opinions ?

Darren
Click to expand...

When I'm running at those kind of power settings, I don't stare at the EFIS, I just keep pulling back on the mixture until she gets rougher than I care to fly, push it a micro-nidge back in, and fly along knowing it is as lean as it will go. I THEN look at the EFIS, and am usually nicely LOP....:cool:

Paul
 
tcrv7 said:
Started Avblend and MMO [Marvel Mystery Oil], yes I know its mineral spirits and wintergreen, but 249 hrs later the rope hasn't been back in that cyl or any other YMMV.
Click to expand...

It sounds crazy, but MMO seems to be working for me as well. A year (or 2) ago I had a stuck exhaust valve on #2 and had an engine shop bust it loose. As it turns out, the valve seat/stem has juuuust enough play in it to allow gunk to build on the stem and caused it to gum up and stick. The mechanic that fixed it advised the use of MMO in the fuel, said the solvent/oil in it should help keep it clean. Like tcrv7 said, I know it's mineral spirits, light oil, animal fat and mint scent, but it seems to be working... it's a coupla hundred hours later and no more issues with that valve.

Regarding lead deposits and build ups, other than that one stuck valve and last month's little piece of crud, my engine seems pretty clean. I'm running dual Pmags, NGK auto plugs and occasional mogas mixed into the 100LL. Not a lot, 10 gallons here and there, 700 or so gallons over 750 hours... my plugs are always clean and never had any lead fouling issues during a run-up. Is this a side benefit of using electronic ignitions? I dunno, but I like it!
 
compression test

Can someone describe the procedure and tools required to do a compression test?

Bevan
 
See the Continental SB

Even though brand C, there's a lot of good info here. http://www.sacskyranch.com/SB03-3.pdf

Personally, I'd look into putting in a borescope and looking at the valve seat. (With the valve open, there should be a shiny spot all around the seat. If there's an area that's dull, the valve is leaking - something (ie., carbon deposit) has built up. That could be the source of your problem and it's not terrible to fix.

Your hours are low for it to be a problem - well before the recommended Lycoming wobble test. But that might be worth doing as well.

Dan
 
Differential Compression tester

You need a differential compression tester and an air compressor, as well as an adapter to fit into your sparkplug hole to connect all the plumbing. I have a similar setup as this one:

http://www.aircraft-tool.com/shop/detail.aspx?product_id=2EM

Comes with instructions, but basically you bring the cylinder up to TDC, connect up the tester with the valve closed, then slowly bring the valve open and apply pressure up to 80psi. The gauge tells you the amount in the cylinder, which is the 'difference' between the pressure in, and the pressure at the cylinder.
sk
 
Darren

You asked a question about running LOP and cleaning the cylinders up. 60-65% power LOP will not clean them up.

Now listen carefully, and all you freaky stressed folk sit on your hands for a minute before jumping on the keyboards.

Take your machine out and do a full power low level run and lean it a bit enough to get a very mild amount of detonation going. You will see this by leaning a litlle and the CHT's shooting up. DO NOT bore along for hours on end with CHT's over 400:eek:, that would be bad, but a short run doing some mild detonation will help clean the heads up.

Now go check your leak down. If there is a valve problem best to fix it sooner than later.

As for running LOP, do it this way, level out....wait a minute or two, pull RPM back to where you are happy, and once you know where the 65% 20F LOP is by fuel flow numbers just rip the mixture back and set a fuel flow. Simple! :)

As for climbing, this is where you could be helped. Target the EGT number on say Cylinder 1 as you go through 500' AMSL (or close to it) and remember that EGT number. then every 2000' in the climb pull back the mixture to get that number. Simple :)

Read and read and read Deakins stuff a lot more so you understand it like he does. Can't learn from a once or twice read.

Cheers

DB:)
 
Darren S said:
I just ordered some TCP from Decalin chemicals and will start using it as soon as it arrives.
Darren
Click to expand...
If you ordered it from Decalin chemicals, you must have ordered Decalin "RunUp Fuel Additive". Cheaper that "TCP" and works better...
 
To Bevan
If you have never done a compression test , please get someone experienced in the task to demonstrate. The process can be potentially dangerous. I have seen a person get hurt when the prop got away while under pressure.
Greg
 
rivetshaver said:
To Bevan
If you have never done a compression test , please get someone experienced in the task to demonstrate. The process can be potentially dangerous. I have seen a person get hurt when the prop got away while under pressure.
Greg
Click to expand...

Thanks. I read through the Skyranch procedure and thought that the prop could easily start swinging if the cyl was not precisely at TDC. My new-to-me mid time engine has a history of consistent high readings (77-78). But since purchase, my mechanic's notes say cylinders 3 and 4 were both 70. I'm not too concerned at this point just wondering how the test is done, and little bit as to why I got two 70's. The engine has been pickled for about 8 months (before the latest comp test) and has since been repickled.

Bevan
 
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