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#1
September 7th 05, 04:17 PM
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Bad cylinder
It turns out that the fouled plug I mentioned last week is oil
fouled... I suspect that the rings have gone... I will borescope the cylinder for damage and check the seal on the intake valve stem, but I suspect the worst... It is burning a quart every 1.5 hours, suddenly... And the story gets complicated... The engine is roughly 1500 smoh... The cylinders are old reruns... The case/crank is ~ 1958 manufacture with nearly 6000 hours in the log book... It is unlikely that Lycoming would take it for core credit... So the options are (in decreasing cost): Factory New (How much? I see, umm, let me get back to you on that.) Factory rebuild - unlikely to get core credit, so total cost about $25k + labor Field overhaul (my mechanic refuses to OH engines anymore so I will have to ship) ~$9K base cost plus parts that won't make it - I'm guessing $15K + If I remove the engine I will have the mount overhauled, new hoses, etc... TOH with 4 new Titan cylinders - ~$4K plus Shipping and Labor 1 new Titan cylinder - ~$1K plus S&L Overhaul the cylinder - maybe $500 total... Overhauling one cylinder gets you into RCR ( russian cylinder roulette)... Both the mechanic and I agree this is not the best route, but it is the cheapest initially... He wants a factory reman to hang, of course... The issue with changing out one cylinder is if one cylinder is gone at 1500 hours, how long before the next one, etc... Doing a TOH at 1500 hours doesn't initially seem cost effective, but it is where I am leaning... The bottoms on 320 150HP engines will, in my experience, go lots longer than the 2000 hour recommended overhaul... If I can get another 1000 hours out of the bottom (2500 total), which is possible, both I and the airplane will likely be retired from flying for other reasons... decisions, decisions... daaayum... denny 
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#2
September 7th 05, 04:53 PM
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: Both the mechanic and I agree this is not the best route, but it is the
: cheapest initially... He wants a factory reman to hang, of course... : The issue with changing out one cylinder is if one cylinder is gone at : 1500 hours, how long before the next one, etc... : Doing a TOH at 1500 hours doesn't initially seem cost effective, but it : is where I am leaning... The bottoms on 320 150HP engines will, in my : experience, go lots longer than the 2000 hour recommended overhaul... : If I can get another 1000 hours out of the bottom (2500 total), which : is possible, both I and the airplane will likely be retired from flying : for other reasons... : decisions, decisions... daaayum... Your "broken ring" theory sounds likely. There are a few issues that may crop up and modify the decision. What I would do is the following: - Borescope all the other jugs and verify only one is burning lots of oil. - Look *carefully* around the exhaust bosses and spark plug holes of all of the jugs. - Pull off the oil filter/screen and take a look inside. See what you find, and how much of it is aluminum/steel, etc. - Rig up a jig for a dial indicator on the valve pushrods If it's a 1500 hour engine, the bottom end should be in good shape still... unless the cam's eaten itself (thus the dial indicator). If there's nothing in the oil filter, even better indication that nothing bad is going on on the bottom end. There may be some gunk for the jug that blew the ring. What may have caused the ring to die? Low octane or lean mixture? There's nothing inherently wrong with a jug going bad after awhile... particularly heat-related cracks. That's no real reason to go down the slippery slope of: "If I overhaul/exhange one jug, should I do them all for a TOH?" "If I'm going to overhaul, maybe I should buy new?" "If I'm going to do a top overhaul, maybe I should split the cases and do the whole thing?" Pull off the bad jug, take a looksee (including the cam lobes you can see from pulling off one jug). If it's just a blown ring and there's nothing visibly wrong with the jug, put a set of rings on it, hone it, and throw it back together. You may have to replace the piston. In any event, I wouldn't let a cracked ring push you to an overhaul if everything else is in good shape. Removing all four jugs is *almost* 4x the work of removing just one. Splitting the case and doing the bottom is a LOT more work and expense. -Cory -- ************************************************** *********************** * Cory Papenfuss * * Electrical Engineering candidate Ph.D. graduate student * * Virginia Polytechnic Institute and State University * ************************************************** ***********************
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#3
September 7th 05, 05:29 PM
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Mike Busch has an article on Avweb where he discusses this topic. His
conclusion seems to be to repair/replace only the affected cylinder. If you repair the cylinder for $500, it only has to last a short while to be more cost effective than the other options. The conclusion seems to be based on the assumption that the failure of one cylinder does not indicate that the others are about to fail.. Mike MU-2 "Denny" wrote in message oups.com... It turns out that the fouled plug I mentioned last week is oil fouled... I suspect that the rings have gone... I will borescope the cylinder for damage and check the seal on the intake valve stem, but I suspect the worst... It is burning a quart every 1.5 hours, suddenly... And the story gets complicated... The engine is roughly 1500 smoh... The cylinders are old reruns... The case/crank is ~ 1958 manufacture with nearly 6000 hours in the log book... It is unlikely that Lycoming would take it for core credit... So the options are (in decreasing cost): Factory New (How much? I see, umm, let me get back to you on that.) Factory rebuild - unlikely to get core credit, so total cost about $25k + labor Field overhaul (my mechanic refuses to OH engines anymore so I will have to ship) ~$9K base cost plus parts that won't make it - I'm guessing $15K + If I remove the engine I will have the mount overhauled, new hoses, etc... TOH with 4 new Titan cylinders - ~$4K plus Shipping and Labor 1 new Titan cylinder - ~$1K plus S&L Overhaul the cylinder - maybe $500 total... Overhauling one cylinder gets you into RCR ( russian cylinder roulette)... Both the mechanic and I agree this is not the best route, but it is the cheapest initially... He wants a factory reman to hang, of course... The issue with changing out one cylinder is if one cylinder is gone at 1500 hours, how long before the next one, etc... Doing a TOH at 1500 hours doesn't initially seem cost effective, but it is where I am leaning... The bottoms on 320 150HP engines will, in my experience, go lots longer than the 2000 hour recommended overhaul... If I can get another 1000 hours out of the bottom (2500 total), which is possible, both I and the airplane will likely be retired from flying for other reasons... decisions, decisions... daaayum... denny
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#4
September 7th 05, 05:35 PM
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Mike Rapoport wrote: Mike Busch has an article on Avweb where he discusses this topic. His conclusion seems to be to repair/replace only the affected cylinder. If you repair the cylinder for $500, it only has to last a short while to be more cost effective than the other options. The conclusion seems to be based on the assumption that the failure of one cylinder does not indicate that the others are about to fail.. I have had cylinder problems too. Fix the bad one and fly.
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#5
September 7th 05, 09:14 PM
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#6
September 7th 05, 09:44 PM
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TripFarmer wrote:
: Personally I wouldn't play Russian Roulette. I wouldn't throw : money away with the TOH with 1500 SMOH and 6000 on the engine. : I did a TOH last year but I had 900 SMOH and 2900TT. So you would overhaul then? I'd say take a look at the avweb article mentioned a few posts back (I *knew* I'd read something to get that mindset). Figure some economics assuming TBO: 1500 hours - 2000 hours is 500 hours of "normal" service. Swap rings in 1 jug: 3-5 hours of labor, $50 in parts minimum, $1500 maximum (if one buys a new jug/piston) Complete top: ^ multiplied by 4 Complete overhaul: $10-15k 500 hours @ $10/hour = $5k "left" in the engine.... definately worth a few jug swaps. -Cory -- ************************************************** *********************** * Cory Papenfuss * * Electrical Engineering candidate Ph.D. graduate student * * Virginia Polytechnic Institute and State University * ************************************************** ***********************
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#7
September 7th 05, 10:57 PM
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This engine isn't too grand anyway you look at it. It is a great
example of why one should go to the till once in awhile to get newer parts thru a factory reman. Another option: If there's nothing busted, just keep running it. Check the spec for oil consumption on the type certificate data sheet. If you are under it, you are OK. You can put a lot of oil in for a cyl overhaul. I had a 520 that was a quart in three then two for a long time. It was a pig but there wasn't really anything wrong with it. Bill Hale
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#8
September 8th 05, 06:33 PM
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Just a follow up... The waters are getting murky...
Flew the plane to my mechanic... This gave us a hot engine for an immediate compression check on the suspect cylinder.. 73/80... No out of round cylinder here and no audible blow by in either the exhaust or crankcase... hmmm... Could be a broken oil ring but the replacement spark plug I put in after finding the oil fouled plug, is clean and dry and firing just fine after 3.5 hours of flight time... hmmm... A check of the other 3 bottom plugs reveals them to be free of oil, but two appear to be running lean and we suspect an air leak ... hmmm... So, where's the oil going all of a sudden? WIth the other cowling off I check the oil separator bottle... Almost empty... hmmm... (I won't elaborate on the oil separator, it uses a quart Mason jar and separates the oil mist from the crankcase and the wet vacuum pump - unless you are really old you have never seen anything like it.) So the brain storming started... the belief at this time is that: 1. a failed bottom plug oiled up because it was not firing and was simply a coincidence, whilst 2. a new induction leak is causing the lean cylinders to burn oil we suspect that the induction leak is in the oil pan The plan at this point is to fly the plane at 23/24 on full rich and measure the oil burn and fuel burn on each engine... Then fly it leaned and recheck the oil burn and fuel burn on each engine.... This is baseline info... Once that is accomplished we will pull the bottom cowl (major job involving disassembly of the air intake system, which is why it waits on the flight test) then ground run it using a can of carb cleaner as a probe to see if we can find a leak... Good thing I own an airplane otherwise I would NEED a hobby to use up all that excess time and money I have... denny
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#9
September 9th 05, 01:59 AM
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In article .com,
"Denny" wrote: Just a follow up... The waters are getting murky... Flew the plane to my mechanic... This gave us a hot engine for an immediate compression check on the suspect cylinder.. 73/80... No out of round cylinder here and no audible blow by in either the exhaust or crankcase... hmmm... Could be a broken oil ring but the replacement spark plug I put in after finding the oil fouled plug, is clean and dry and firing just fine after 3.5 hours of flight time... hmmm... A check of the other 3 bottom plugs reveals them to be free of oil, but two appear to be running lean and we suspect an air leak ... hmmm... So, where's the oil going all of a sudden? WIth the other cowling off I check the oil separator bottle... Almost empty... hmmm... (I won't elaborate on the oil separator, it uses a quart Mason jar and separates the oil mist from the crankcase and the wet vacuum pump - unless you are really old you have never seen anything like it.) So the brain storming started... the belief at this time is that: 1. a failed bottom plug oiled up because it was not firing and was simply a coincidence, whilst 2. a new induction leak is causing the lean cylinders to burn oil we suspect that the induction leak is in the oil pan The plan at this point is to fly the plane at 23/24 on full rich and measure the oil burn and fuel burn on each engine... Then fly it leaned and recheck the oil burn and fuel burn on each engine.... This is baseline info... Once that is accomplished we will pull the bottom cowl (major job involving disassembly of the air intake system, which is why it waits on the flight test) then ground run it using a can of carb cleaner as a probe to see if we can find a leak... Good thing I own an airplane otherwise I would NEED a hobby to use up all that excess time and money I have... denny There could be a reason for the bad plug. Pull the cowl and check the "cigarette" leads at the plugs for crud, streaking, carbon. This condition will cause misfiring and poor performance. You can pull the cigarettes loose and clean the insides (and the insulation) with either denatured alcohol or lacquer thinner.
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#10
September 9th 05, 04:23 AM
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"Denny" writes:
Once that is accomplished we will pull the bottom cowl (major job involving disassembly of the air intake system, which is why it waits on the flight test) then ground run it using a can of carb cleaner as a probe to see if we can find a leak... On cars, a propane torch tank and head, sometimes with an added hose, are used to find vacuum leaks... and it makes no mess. -- A host is a host from coast to & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
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