If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Oil leak on top of the engine
It seems to be the season for finding oil leaks.
At our completely uneventful annual (just finished two days ago) I asked my shop to investigate a new leak that I had detected when I de-cowled the engine for the inspection. All across the top of our 3-year-old, 500-hour engine, down the seam where the case halves join together, right where the push rods attach to the case, was a puddle of fresh, clean oil -- enough to look like I had just spilled some while adding oil... Trouble was, I HADN'T added any oil recently. With our new air/oil separator, I no longer need to add oil between oil changes, so it had been some 24 flight hours since I had last added oil. With no obvious source of the leak, my mechanic thoroughly cleaned the engine and resolved to fly it to see where the oil was coming from. The flying weather wouldn't cooperate until today, but this morning we flew the plane on its post-annual test flight, found a squawk or two, and returned to the shop to fix these and check for the source of the leak. The total flight time was only 0.7 hours, yet the top of the engine once again looked like I had spilled oil while filling. It was right along the case halves seam, so with no other apparent source my mechanic figured the first place to start was to check the torque on the case bolts. He reached for the first one, and we were both astounded when he was able to tighten it -- by hand! One by one, all of the case nuts were found to be very loose (although that was the only one that was hand-tight), and needed to be re-torqued to 190 inch pounds of torque. After tightening those, he checked the prop governor housing, and found those bolts to be way loose, too. Essentially the whole top of the engine was loose, and oil was leaking at the seam. After re-torquing everything to spec, I test flew the plane for another 0.5 hours, and was happy to see everything bone dry once again. Questions: 1. Is this something one should expect after 500 hours of shaking and rattling? Do these bolts just plain loosen over time, going from hot to cold hundreds of times? 2. Do you guys re-torque these bolts on a schedule? 3. Is this something your A&P checks at every annual? My guys were clearly surprised to find these bolts so loose -- and they are the guys who rebuilt the engine. 4. Are there any other bolts -- say, on the BOTTOM of the engine -- that I should check for looseness? I looked but couldn't see any. 5. Should I apply LocTite to these bolts? I suspect I'll be checking those bolts regularly from now on! -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" |
#2
|
|||
|
|||
No they shouldn't be that loose. Torqueing a bolt is to put a higher load
on it then the load it sees in service. It wasn't torqued to begin with or something else has changed.. I would check all the cylinder holdown nuts and thru-bolts before I flew it again. Lyc or TCm has a service bltn explaining how to measure the rotating resistance of the engine by using a spring scale on the prop. Take a measurement then torque the thru bolts then take another measurement. A significant change is signs of bearing pinch. Good luck and hope for the best. Kent Felkins |
#3
|
|||
|
|||
"Fly" wrote in message ... No they shouldn't be that loose. Torqueing a bolt is to put a higher load on it then the load it sees in service. It wasn't torqued to begin with or something else has changed.. I would check all the cylinder holdown nuts and thru-bolts before I flew it again. Lyc or TCm has a service bltn explaining how to measure the rotating resistance of the engine by using a spring scale on the prop. Take a measurement then torque the thru bolts then take another measurement. A significant change is signs of bearing pinch. Good luck and hope for the best. Kent Felkins This one gets my vote for thread of the week, I will watch out for this from now on. I am suprised its not on the annual check list. In fact, I may have to go check for that. |
#4
|
|||
|
|||
A significant change is signs of bearing pinch.
What's "bearing pinch"? Dunno if this matters, but all compressions are in the high 70s, oil consumption is better than average, and it runs great. -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" |
#5
|
|||
|
|||
DAMN!
No, that's absolutely not normal. Poor workmanship at the rebuilder. There are bolts that should have been retorqued at a certain hour. The shop would have specified which ones. I really don't know of anyone who makes it a habit to check the torque on all the engine bolts at each annual. Things like exhaust studs hardware and intake bolts are checked. Understand this. If the case is fretting, as it does when bolts are loose, it's a very serious situation. If this were my engine, I would have another mechanic check the torque of the through bolts. If they're off you need to clean it up very well and run it for about another 1/2 hour on the ground. Do Not Fly This Airplane. If wet, the engine needs to be pulled and the disassembled, cases sent out and reassembled. It'll give you something to talk about, anyway. Don't take my word for it, contact a real engine house for advice and let the world know if I'm wrong. I seem to remember being strongly criticized after saying something about soliciting recommendations for a shop via the newsgroups when you did it a few years back. On Thu, 10 Feb 2005 21:25:10 GMT, "Jay Honeck" wrote: It seems to be the season for finding oil leaks. At our completely uneventful annual (just finished two days ago) I asked my shop to investigate a new leak that I had detected when I de-cowled the engine for the inspection. All across the top of our 3-year-old, 500-hour engine, down the seam where the case halves join together, right where the push rods attach to the case, was a puddle of fresh, clean oil -- enough to look like I had just spilled some while adding oil... Trouble was, I HADN'T added any oil recently. With our new air/oil separator, I no longer need to add oil between oil changes, so it had been some 24 flight hours since I had last added oil. With no obvious source of the leak, my mechanic thoroughly cleaned the engine and resolved to fly it to see where the oil was coming from. The flying weather wouldn't cooperate until today, but this morning we flew the plane on its post-annual test flight, found a squawk or two, and returned to the shop to fix these and check for the source of the leak. The total flight time was only 0.7 hours, yet the top of the engine once again looked like I had spilled oil while filling. It was right along the case halves seam, so with no other apparent source my mechanic figured the first place to start was to check the torque on the case bolts. He reached for the first one, and we were both astounded when he was able to tighten it -- by hand! One by one, all of the case nuts were found to be very loose (although that was the only one that was hand-tight), and needed to be re-torqued to 190 inch pounds of torque. After tightening those, he checked the prop governor housing, and found those bolts to be way loose, too. Essentially the whole top of the engine was loose, and oil was leaking at the seam. After re-torquing everything to spec, I test flew the plane for another 0.5 hours, and was happy to see everything bone dry once again. Questions: 1. Is this something one should expect after 500 hours of shaking and rattling? Do these bolts just plain loosen over time, going from hot to cold hundreds of times? 2. Do you guys re-torque these bolts on a schedule? 3. Is this something your A&P checks at every annual? My guys were clearly surprised to find these bolts so loose -- and they are the guys who rebuilt the engine. 4. Are there any other bolts -- say, on the BOTTOM of the engine -- that I should check for looseness? I looked but couldn't see any. 5. Should I apply LocTite to these bolts? I suspect I'll be checking those bolts regularly from now on! |
#6
|
|||
|
|||
On 2/10/2005 15:12, Jay Honeck wrote:
A significant change is signs of bearing pinch. What's "bearing pinch"? Dunno if this matters, but all compressions are in the high 70s, oil consumption is better than average, and it runs great. From my automotive days, this is where the bearings are either not seated properly, or are not the proper size to fit, and torquing down the case bolts results in compressing the bearings onto the crank, resulting in restricted movement and generally a chewing up of the bearings and/or crank. -- Mark Hansen, PP-ASEL Sacramento, CA |
#7
|
|||
|
|||
"Jon A." wrote:
I really don't know of anyone who makes it a habit to check the torque on all the engine bolts at each annual. Things like exhaust studs hardware and intake bolts are checked. The case bolts on my previous Continental IO-520, circa 1987, had white paint stripes painted on them to indicate whether they had come loose. The previous owner, a one-time automotive racer, had a colorful name for these stripes but at the moment I cannot recall it. -- Peter ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#8
|
|||
|
|||
On Thu, 10 Feb 2005 18:51:03 -0500, "Peter R."
wrote: "Jon A." wrote: I really don't know of anyone who makes it a habit to check the torque on all the engine bolts at each annual. Things like exhaust studs hardware and intake bolts are checked. The case bolts on my previous Continental IO-520, circa 1987, had white paint stripes painted on them to indicate whether they had come loose. The previous owner, a one-time automotive racer, had a colorful name for these stripes but at the moment I cannot recall it. You can use a product called "Torque Seal", available from Spruce for this. All of your fuel connections should be done. Doesn't actually seal the torque, but shows you if something has moved. |
#9
|
|||
|
|||
"Jon A." wrote:
You can use a product called "Torque Seal", available from Spruce for this. All of your fuel connections should be done. Doesn't actually seal the torque, but shows you if something has moved. I think I now recall the name the previous owner called those paint stripes. "Sabotage spotter." -- Peter ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#10
|
|||
|
|||
What's "bearing pinch"? Severe case of the crankcase halves rubbing against each other and over time grinding away. Thus the bore for that crank bearing is smaller. It keeps working ok for a while because its a loosed fit. But if you retorque the thru bolts you'll squeeze the bore back tighter and its smaller diameter will pinch the bearing halves together, and maybe cause direct metal to metal contact between the crank and bearing. Many engines have dowel pins that fit the halves together to minimize fretting. Btw, I don't have the torque value bulletin handy but it seems tha the case spine bolts are only torqued down to 7-10 ft lbs. Not that much but definitely more than finger tight! Kent Felkins |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
ROP masking of engine problems | Roger Long | Owning | 4 | September 27th 04 07:36 PM |
Proposals for air breathing hypersonic craft. I | Robert Clark | Military Aviation | 2 | May 26th 04 06:42 PM |
My Engine Fire!! | [email protected] | Owning | 1 | March 31st 04 01:41 PM |
Car engine FAA certified for airplane use | Cy Galley | Home Built | 10 | February 6th 04 03:03 PM |
Corky's engine choice | Corky Scott | Home Built | 39 | August 8th 03 04:29 AM |