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  #1  
Old 07-15-2020, 07:08 PM
Drippy Drippy is offline
 
Join Date: Nov 2015
Location: Vermont
Posts: 123
Default Oil leak - or blow by????

I am been fighting high oil consumption since my first flight. I will try to quickly lay out the situation in the hopes someone out there has a suggestion.

I rebuilt my IO540 C4B5 with the help of a local A&P shop - it has 125 hours on it when I rebuilt it - it had been involved in an aircraft fire but the engine was not directly involved but since we were concerned about corrosion we took it down and rebuilt it with new bearing, hardware and gaskets. It has been functioning well in all regards for 260 hours since except I have had to replace 1 quart of oil every 4-5 hours. I added a slime fighter to the breather and it appears to have had some effect reducing consumption from .22 to .18 quarters an hour.

I run it at 7 qts and I refill when it hits the 6 line.

I have oil under the cowl it seems to be mostly on the left rear side and I also see oil drip from the breather.

The oil does turn dark but not right after an oil change.

I have checked the exhausts and they don't seem very oily.

I spoke with Antisplat about there system and they suggested I apply 5 PSI of air to the crank to look for an oil leak using the soapy water trick. I found a couple of very small leaks - one around the cover plate for the missing MAG - light speed instead. But flying since I fixed this I am still getting the same mess under the cowl and on the belly.

I have looked at most the oil leak type posts on the forum and tried many of the ideas I found including the foot powder - ground run trick but didn't see any leaks.

Any suggestions for the next step?


Thanks
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Mike
N95VT
RV10
~300hrs flying
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  #2  
Old 07-15-2020, 08:52 PM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 5,516
Default

Quote:
Originally Posted by Drippy View Post
I am been fighting high oil consumption since my first flight. I will try to quickly lay out the situation in the hopes someone out there has a suggestion.

I rebuilt my IO540 C4B5 with the help of a local A&P shop - it has 125 hours on it when I rebuilt it - it had been involved in an aircraft fire but the engine was not directly involved but since we were concerned about corrosion we took it down and rebuilt it with new bearing, hardware and gaskets. It has been functioning well in all regards for 260 hours since except I have had to replace 1 quart of oil every 4-5 hours. I added a slime fighter to the breather and it appears to have had some effect reducing consumption from .22 to .18 quarters an hour.

I run it at 7 qts and I refill when it hits the 6 line.

I have oil under the cowl it seems to be mostly on the left rear side and I also see oil drip from the breather.

The oil does turn dark but not right after an oil change.

I have checked the exhausts and they don't seem very oily.

I spoke with Antisplat about there system and they suggested I apply 5 PSI of air to the crank to look for an oil leak using the soapy water trick. I found a couple of very small leaks - one around the cover plate for the missing MAG - light speed instead. But flying since I fixed this I am still getting the same mess under the cowl and on the belly.

I have looked at most the oil leak type posts on the forum and tried many of the ideas I found including the foot powder - ground run trick but didn't see any leaks.

Any suggestions for the next step?


Thanks
Oil under the cowl comes from somewhere and primarily goes down. Let the plane sit and come back and look very carefully from the bottom of the engine with a good light (may need mirror) look for hanging drops. Locate all the drops and go the the highest area that could be leaking. Seal from the top down. You may have multiple small weeps. I found that resetting a mag without a new gasket leaked. A cover plate installed by Lycoming was missing a gasket. I had two leaks on the Vans sensor manifold where a sensor and oil hose attached. My head drain back hose all leaked and it was repaired with constant force spring clamps. A bit tricky to install, but well worth the effort.

I am a strong definitive diagnosis guy and always attempt to find the specific area to repair, but I have not found a way to static/ground check for oil leaks from the pressurized system. Pressurizing the crankcase is a good method for gaskets.

Edit: the dye method is good, I have some on the shelf with a UV light awaiting the next leak.
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Bill

RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”

Last edited by BillL : 07-16-2020 at 06:41 AM.
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  #3  
Old 07-15-2020, 09:15 PM
VA Maule VA Maule is offline
 
Join Date: Apr 2016
Location: Bucking ham, Virginia
Posts: 208
Default Mystery oil

What are your cylinder leak down tests running? If one or more having low readings that you can hear the air escaping via the oil filler/dipstick tube or crankcase vent tube would account for higher than normal case pressure that can make oil just seem to appear on the engine.
Another often overlooked leaky location are the cylinder head drain line rubber hoses they will seep oil particularly the old certified type that's nothing more than common rubber fuel line.oil will wick out through the reinforcing cords. Replace the rubber hoses with automatic transmission cooler hose which is intended for use with hot oil ( common rubber hose breaks down with constant contact with hot oil from the inside, gets to the reinforcement cords and wicked out the cut ends). Also use constant tension spring clamps instead of worm gear clamps , as the rubber extrudes through the slots in clamp and squeezes out from each side compression force is lost causing leeks.
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  #4  
Old 07-15-2020, 09:33 PM
bpattonsoa bpattonsoa is offline
 
Join Date: Apr 2005
Location: Indepenence, Oregon
Posts: 342
Default

We had a persistent undetectable minor leak when I was Crew Chief on a Reno racer with a Continental six. Finally convinced the pilot to buy a UV dye kit for autos. First completely clean the motor with solvent spray, really clean. Then add the dye. Run it uncowled just a minute, then scan with the light. If you don’t find it, run a little longer. If you have several leaks, keep at it.

Fix, re-clean and do it again. When finally tight, replace the oil. You may end up repeating it several times.

Our leak was inside the engine mounted oil cooler.
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Rans S-20 Raven 796S flying since 2019 (slowly)
RV-6A 596S flying since '99 (Sold)
HP-18 5596S flying since '89
RV-10 996S flying since 2014, quick build wing and slow build fues., - dual Skyviews with complete system, two radio and not much else. Interior completely finished with Zolatone. CF plenum. 1624 lbs, FLYING after a 21.5 month build.
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  #5  
Old 07-16-2020, 06:28 AM
Drippy Drippy is offline
 
Join Date: Nov 2015
Location: Vermont
Posts: 123
Default Leak down Test

Thanks for all the good suggestions.

I have been trying the top down search approach - I have long had a suspicion that oil my be leaking from my oil dipstick cap or #6 push road tube.

The oil cap for my engine has the tension type not the screw on style. I replaced the o-ring and it feels like it seats tightly - but I see what appears to be a lite sheen on my number 6 cylinder area aft of the oil cap nothing pooling or dripping just the appears of a lite sheen. But when I wipe it with a clean cloth I don't see any oil residue either.??? I have also never found the oil cap to be lifted and not fully seated in my post flight inspections so if it is getting past it must be in the closed position or from the base. Possibly a good chance to use the oil dye.

I did try ground runs using the foot powder approach and couldn't find any oil leaks though I only took the engine up to ~2K RPM to cycle the prop and then do another visual inspection. I applied foot powder to the oil cap, push rod ends, all the oil return lines, sump and case parting lines ect and didn't see any indications of leaks. But . . .

I am not sure exactly what a leak down test is?? My compression tests were all good 76+ on a warm engine.
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N95VT
RV10
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  #6  
Old 07-16-2020, 07:47 AM
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9GT 9GT is offline
 
Join Date: Jan 2010
Location: Southern Michigan
Posts: 1,966
Default

We had a heck of a time tracking down a minor oil leak on my buddies Superior IO-360 powered Cozy MKIV. Finally tried the oil dye and UV light to find it. Leak was on the top case split. We ended up cleaning the area well and de-greasing with spray brake cleaner and drying it with compressed air several times. Then pulled a vacuum in the case with a vacuum cleaner and applied a few drops of Loctite green under vacuum. Cleaned up the access and let it sit a day. We then slathered on some tank sealant over the area and cowling let it cure. Not the prettiest fix but it seems to have worked.
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  #7  
Old 07-17-2020, 05:12 AM
mlinett mlinett is offline
 
Join Date: Jul 2015
Location: denton
Posts: 10
Default Crush washer

Check the crush washers. We had a big leak on one. It took months to find it.
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  #8  
Old 07-17-2020, 05:24 AM
flysrv10 flysrv10 is online now
 
Join Date: Jan 2010
Location: Florida
Posts: 267
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Oil adjustment/check valve crush washer and the screw shaft (if you have that type) on the right side and how about the prop seal? If you have the split seal, I can almost guarantee that it leaks or will leak.
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  #9  
Old 07-17-2020, 05:39 AM
Drippy Drippy is offline
 
Join Date: Nov 2015
Location: Vermont
Posts: 123
Default oil temp adjust crush washer

I will definitely check the oil temp adjust valve mine is on the right side.

As for the shaft seal - long story there - as I was doing my engine runs on deck one of the local A&Ps suggested it might be the shaft seal and to check to see if it was slipping. So a buddy and I pulled the prop inspected it and found no evidence of leaking and the seal didn't move when we pushed on it as suggested by the A&P.

But last week when I started to do the air pressure test - putting positive pressure in the case - I heard air escaping from that area - pulled the prop again and clearly had bubbling from the bottom of the shaft seal when I sprayed it with soap and water. I was careful never to apply more then 5psi but was using a harbor freight regulator - I am not sure if I might have "blown" out the shaft seal?? Anyway that same buddy helped me replace the shaft seal and reinstall the prop - 48 hours later- ground run no leaking - 30 minute flight test - same oil accumulating on the top of the Air Filter, front landing gear cross member (next to firewall) and on the belly.
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N95VT
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  #10  
Old 07-17-2020, 06:09 AM
flysrv10 flysrv10 is online now
 
Join Date: Jan 2010
Location: Florida
Posts: 267
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Quote:
Originally Posted by Drippy View Post
I will definitely check the oil temp adjust valve mine is on the right side.

As for the shaft seal - long story there - as I was doing my engine runs on deck one of the local A&Ps suggested it might be the shaft seal and to check to see if it was slipping. So a buddy and I pulled the prop inspected it and found no evidence of leaking and the seal didn't move when we pushed on it as suggested by the A&P.

But last week when I started to do the air pressure test - putting positive pressure in the case - I heard air escaping from that area - pulled the prop again and clearly had bubbling from the bottom of the shaft seal when I sprayed it with soap and water. I was careful never to apply more then 5psi but was using a harbor freight regulator - I am not sure if I might have "blown" out the shaft seal?? Anyway that same buddy helped me replace the shaft seal and reinstall the prop - 48 hours later- ground run no leaking - 30 minute flight test - same oil accumulating on the top of the Air Filter, front landing gear cross member (next to firewall) and on the belly.
It sounds like it is still leaking from the prop seal. If you are sure you don't have a leak from the seal, OK. But if you have to redo; get two non split seals, one to screw up one to install. Use pliobond contact cement and the right tool to pull over the prop flange. Make dang sure the seating area and the seal are squeaky clean. Make sure the groove is also clean. Use an angle pic to dig out the stuff out of the groove. No need to wait for pliobond to get tacky. Install wet and wait overnight. You can then forget the seal for a long time.
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