!!. Flown in a conservative way. Any advise? Hope everything goes well because im going to the atlantic coas to fly with tourists this summer and get the hours for the instructor course.Un abrazo
fede
Low comp cylinders
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
Low comp cylinders
Pals, the repaired exhaust of LV-FEH arrived, but my A&P told me that he is going to remove two low compression cylinders to check for rings alignment before installing exhaust (Engine is only 50 SMOH) with actually 25 hours flown, ask why later !!. Flown in a conservative way. Any advise? Hope everything goes well because im going to the atlantic coas to fly with tourists this summer and get the hours for the instructor course.
Un abrazo
fede
!!. Flown in a conservative way. Any advise? Hope everything goes well because im going to the atlantic coas to fly with tourists this summer and get the hours for the instructor course.Un abrazo
fede
I'm not sure what you mean by "flown in a conservative way", but normally flying a new engine gently is not a good idea. High manifold pressures (wide open throttle) and low altitudes (high manifold pressure and good dense air for cooling) is best for seating new rings. I don't know how low your compression is in the cyls in which he believes the rings are improperly aligned, but if they're not too low, I'd recommend just flying them hard for a few hours and see if they don't seat. After 10 hours if they are still low, then pull them and re-hone and reassemble with new rings again, and break them in correctly. (This advise is assuming there's no problem other than aligned or unseated rings. Look in the cyls for scored/scratched walls indicating a broken ring first.)
low comp cyls
George, well first, with conservative way i mean, things as no more than 2300 rpm in cruise, but because that is the way i was taught to fly, But after reading a lot and being in this and the old forum i think that i was not very well taught. i bought the plane with about 25 hours on it, flight well, climb OK. after that it has flown about other 25 hours, with one oil change. I flew about 10 of that hours (long story). the comp was about (if i dont remember wrong) 50/80, I was thinking of telling the A&P ( he is actually an USA A&P license holder and former Air force and airline mechanic) that he left the cyls the way they are and fly a bit more to see what happens, well i´m in favor to that. But well dont know what to do, because lots of mechs dont behave well on my stuff. More advice welcome
See ya!
Fede
See ya!
Fede
stop him!!!
george, finally stopped my mechanic from removing cylinders, hope everything goes well here, if not, you´ll have my body wandering around the states soon.
My best regards
FEDE
My best regards
FEDE
YALL COME ON OVER HERE
FEDE,
DON'T WAIT FOR "THINGS" TO GO BAD TO VISIT. COME ON OVER! IF YOU GET ANYWHERE NEAR THE LOUISIANA/ TEXAS BORDER, YOU MUST PLAN TO MAKE A STOP HERE. WE WILL HAVE A SPECIAL GET TOGETHER. WE CAN CALL OURSELVES AN "INTERTNATIONAL 170 FLY-IN"! I DID HAVE A SWISS FLYER STOP HERE IN AN ULTRA LIGHT AMPHIBIOUS AIRCRAFT, BUT IT HAS BEEN A WHILE BACK.
THE WELCOME MAT IS ALWAYS OUT FOR FLYERS HERE AT TOLEDO BEND.
DON'T WAIT FOR "THINGS" TO GO BAD TO VISIT. COME ON OVER! IF YOU GET ANYWHERE NEAR THE LOUISIANA/ TEXAS BORDER, YOU MUST PLAN TO MAKE A STOP HERE. WE WILL HAVE A SPECIAL GET TOGETHER. WE CAN CALL OURSELVES AN "INTERTNATIONAL 170 FLY-IN"! I DID HAVE A SWISS FLYER STOP HERE IN AN ULTRA LIGHT AMPHIBIOUS AIRCRAFT, BUT IT HAS BEEN A WHILE BACK.
THE WELCOME MAT IS ALWAYS OUT FOR FLYERS HERE AT TOLEDO BEND.
oil and visit
George, i´ve been using Mobil aero100 oil. i think is sae 50
Flyguy, Thanks a lot for your invitation, but i wasn´t planning to go with the LV-FEH, because it will be too expensive for my current economical position, i was meaning go to the states to search for a better future if my country really goes bad, i don´t want to waste all my spirit here
. Well who know, perhaps if i could do sometihng with it there, just maybe ill go with him.
Some 170ers i´ve met trough the net have been very kind like you, and i appreciate that a lot. you´re welcome here in bolson as well as the other pilots in this and the old forum. Or in pinamar (in the atlantic coast) where i think ill be this summer.
My best regards for you two
Fede
Flyguy, Thanks a lot for your invitation, but i wasn´t planning to go with the LV-FEH, because it will be too expensive for my current economical position, i was meaning go to the states to search for a better future if my country really goes bad, i don´t want to waste all my spirit here
. Well who know, perhaps if i could do sometihng with it there, just maybe ill go with him.Some 170ers i´ve met trough the net have been very kind like you, and i appreciate that a lot. you´re welcome here in bolson as well as the other pilots in this and the old forum. Or in pinamar (in the atlantic coast) where i think ill be this summer.
My best regards for you two
Fede
Several years ago while doing an annual one of my cylinders was down to 48 or 50 while the rest were in lower 70's range. My very experienced AI pronounced the rings to be stuck in the grooves and proceeded to squirt about 50cc's of Marvel Mystery oil in the upper spark plug hole. He then replaced the plug and instructed me to very gently rock the prop against compression on said cylinder for a few minutes. We went to eat lunch and rocked the prop a few times on our return and pulled the bottom plug to purge the remaining mystery oil. Replaced the plugs,cowled the engine and left with instructions to check compression in about 10 hours. As things usually go the compression didn't get checked until the next annual, but the next two annuals that cylinder was higher than any other. I used that trick two other times with similar results. Sure a lot easier than changing a jug!
Paul
Paul
Well guys, after flying about 35 hours since the plane was back to air in november, i think i still had 3 cyls with low compression, But as i only tested them by hand, i decided to buy a compression tester, test them, and them see what im gonna do with this. Last time i tested them with my mech 3 cyls were leaking trough the engine breather (rings?). Days ago i pull all the spark plugs out, and found one lower really flooded with oil, and two others lower ones a bit humid with oil, the other lower ones were fine. I decided this after doing a flight and the plane started (after 5 min of flight) to shake a bit, not much, i guess that could be a plug, happened to me before in other planes, but i think this is an advice to do something with those cyls. AH! i forgot, in take off the engine just got 2300 rpm, obviously it took a lot of the runway to take off and then the climb was not very high (4 people and half tank), or at least that was what i felt. Any other advice than the stated before on this topic. How much of the work could be done by an unexperienced owner like me. Un abrazo a todos desde el sur.
Usually oil fouled plugs are the result of worn valve guides, especially if there's a lot of blue engine smoke upon start-up. (After shut-down oil leaks into the cylinder past the worn guides, and pools in the cylinder usually fouling the lower spark plugs.) But broken/worn rings can also do it.
If you've got automotive experience, it's not a hard job to change cylinders/pistons. But be careful when torquing the cylinder-base bolts. Some of those are actually through-bolts that go all the way to the other cylinder. Excessive torque on a mid-life engine can seize the crankshaft main bearings and too little torque can let the bearings spin. That will lead to oil starvation of the bearing because the oil squirt-holes in the bearing will lose orientation with the oil passages in the crankcase. (Little secret: Before disassembly of the bolts, use your torque wrench to attempt to tighten those bolts/nuts. Notice at what torque the nuts begin to move/tighten. That is the minimum torque to use on reassembly. The maximum is that specified in the overhaul manual, 430 in-lbs for 3/8" studs, and 510 in-lbs for 7/16" studs.) Remember to use new cyl base O-ring seals. You are going to need to buy or borrow at least those Continental cylinder wrenches (I seem to recall their actual nut sizes are 1/2" and 5/8") to do the job with a torque wrench. You cannot measure torque otherwise. Now is the time to buy a set of them thru TradeAPlane (San Val, etc.). They'll pay for themselves. (And you may also have to grind a 5/8" box-end wrench (closed-end or "loop" spanner for you Commonwealth blokes) pretty thin and alter the handle slightly to fit one of those studs, although an "S"-shaped wrench sometimes works. If you look in a Continental engine mechanic's toolbox, you'll usually find a 5/8" combination wrench that's been modified and has a well-worn look to it.)
Don't let those connecting rods bang against the crankcase when you pull the cylinder off the piston. It will mark the rod and set up a stress-fracture point. Wrap the rod in newspaper to protect it while disassembled or support it with a string "cats-cradle" from the cyl studs.
This is a great time to order the TCM Overhaul Manual from Aircraft Spruce, before you begin the work.
Good luck.
If you've got automotive experience, it's not a hard job to change cylinders/pistons. But be careful when torquing the cylinder-base bolts. Some of those are actually through-bolts that go all the way to the other cylinder. Excessive torque on a mid-life engine can seize the crankshaft main bearings and too little torque can let the bearings spin. That will lead to oil starvation of the bearing because the oil squirt-holes in the bearing will lose orientation with the oil passages in the crankcase. (Little secret: Before disassembly of the bolts, use your torque wrench to attempt to tighten those bolts/nuts. Notice at what torque the nuts begin to move/tighten. That is the minimum torque to use on reassembly. The maximum is that specified in the overhaul manual, 430 in-lbs for 3/8" studs, and 510 in-lbs for 7/16" studs.) Remember to use new cyl base O-ring seals. You are going to need to buy or borrow at least those Continental cylinder wrenches (I seem to recall their actual nut sizes are 1/2" and 5/8") to do the job with a torque wrench. You cannot measure torque otherwise. Now is the time to buy a set of them thru TradeAPlane (San Val, etc.). They'll pay for themselves. (And you may also have to grind a 5/8" box-end wrench (closed-end or "loop" spanner for you Commonwealth blokes) pretty thin and alter the handle slightly to fit one of those studs, although an "S"-shaped wrench sometimes works. If you look in a Continental engine mechanic's toolbox, you'll usually find a 5/8" combination wrench that's been modified and has a well-worn look to it.)
Don't let those connecting rods bang against the crankcase when you pull the cylinder off the piston. It will mark the rod and set up a stress-fracture point. Wrap the rod in newspaper to protect it while disassembled or support it with a string "cats-cradle" from the cyl studs.
This is a great time to order the TCM Overhaul Manual from Aircraft Spruce, before you begin the work.
Good luck.
George, seems i got some time of working on the plane after you told me. First of all i think ill buy a compression tester. Then see what to do. Seems that many owners here fly their engines with very low compression on six cyls, dont ask me why, because i dont know. I prefer to be safe. Mmm, i think ill start to look on the prices for all that i will need to do the job (any advice on that?) If the problem is a worn guide, what is the solution? I really have lots of questions for you guys, as you know im not a very experienced pilot/owner, but i dont know where to start. What do you think of what happened on the flight. Do you think it will be safe to fly with those 3 cyls on low comp or with all the oil in the plugs. AH antoher thing, right exhaust stack has more black deposits than left one, and right is where i found the oily plug. Hope not to bother you with all this.
The oily cylinders will explain the black/sooty exhaust. The question is: What suddenly developed to cause the oily cylinders?
That's where a physical examination, and a compression test will be useful.
Low compression in and of itself is not necessarily a concern. The cause of the low compression is the greater interest.
If a compression test reveals low compression with leaking past the valves, then removal/repair of the cylinder/valves are in order. If the leak is NONE past the exhaust valve, and only slightly past the intake valve, with mostly past the rings (hissing air noises found at the oil filler cap), then the subjective decision must be made whether or not to continue to operate or to make a repair. Generally, if the compression is 45/80 or better, with leaking only past rings, I'd recommend flying the airplane another 5 or 10 hours and performing the test again. This action/recommendation would require that no steel is found in the oil screen/filter and no obvious deep scratches in the cylinder walls that might be caused by a broken ring.
If the oily cylinder/oil-fouled plugs are a sudden development, I'd recommend removing the valve covers and rotating the prop to bring that piston to top-dead-center and attempt to "wiggle" the valves. In other words, look thru the valve springs and attempt to discover if a broken valve guide or a heavily worn valve guide allows the valve to move significantly. (I once had a plug suddenly display oil fouling, and the cylinder had erratic compression readings. One test would be 70/80 and the next 55/80, then 60/80, etc etc. The valve guide was cracked and broken allowing the valve to seat inconsistently on it's face/seat. Further operation would likely have resulted in a swallowed valve and emergency landing.
Alterfede, there is no way we can use this forum to adequately advise you with regard to evaluating this engine problem in anything other than a general way. Engine diagnosis must be done first hand, and I don't see how to treat the subject with the respect it deserves via long-distance or messaging system. I believe you are going to need the advice of an experienced engine mechanic who personally examines the engine and works with you on this.
That's where a physical examination, and a compression test will be useful.
Low compression in and of itself is not necessarily a concern. The cause of the low compression is the greater interest.
If a compression test reveals low compression with leaking past the valves, then removal/repair of the cylinder/valves are in order. If the leak is NONE past the exhaust valve, and only slightly past the intake valve, with mostly past the rings (hissing air noises found at the oil filler cap), then the subjective decision must be made whether or not to continue to operate or to make a repair. Generally, if the compression is 45/80 or better, with leaking only past rings, I'd recommend flying the airplane another 5 or 10 hours and performing the test again. This action/recommendation would require that no steel is found in the oil screen/filter and no obvious deep scratches in the cylinder walls that might be caused by a broken ring.
If the oily cylinder/oil-fouled plugs are a sudden development, I'd recommend removing the valve covers and rotating the prop to bring that piston to top-dead-center and attempt to "wiggle" the valves. In other words, look thru the valve springs and attempt to discover if a broken valve guide or a heavily worn valve guide allows the valve to move significantly. (I once had a plug suddenly display oil fouling, and the cylinder had erratic compression readings. One test would be 70/80 and the next 55/80, then 60/80, etc etc. The valve guide was cracked and broken allowing the valve to seat inconsistently on it's face/seat. Further operation would likely have resulted in a swallowed valve and emergency landing.
Alterfede, there is no way we can use this forum to adequately advise you with regard to evaluating this engine problem in anything other than a general way. Engine diagnosis must be done first hand, and I don't see how to treat the subject with the respect it deserves via long-distance or messaging system. I believe you are going to need the advice of an experienced engine mechanic who personally examines the engine and works with you on this.
George, the oily cyls are not suddendly, they appeared at annual last year, and the air leaks were on the engine breather. If i remove the valve covers the gaskets still could be used or if theyre cork i have to put another stuff to seal them? HOpe nothing big happened, because the engine has 70 hs smoh. It will be a pity. How do i check for scratches, look with a light trough the plug hole? CAn happen that the rings never seated well and the oil passes to the chamber? GEorge, i ask all this to try to figure most i can before taking a decision, first off all visual check and when the tester arrives see the compression and where is the leak.