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Oil leak - or blow by????

Drippy

Well Known Member
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
 
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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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.
 
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.
 
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.
 
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.
 
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.
 
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.
 
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.
 
Prop Seal

Well I better not tell my buddy we need to pull the prop again:).

Is leaking only airborne - or I assume higher MAP commonly associated with a prop seal leak?

We used a single piece seal - I cleaned like crazy to include with a pick - the grove was clean and used emery cloth on the shaft - it was clean.

We then used the prescribed DOW 737 sealant.

We did not use the prescribed tool to stretch it, but heated the seal and it pulled over the prop hub fairly easily - inspecting it prior to installing the spring and putting it in place it appeared undamaged.

Prior to pulling the prop again - I might try putting some foot powder on the visible portion of the case below the prop seal to see if I get any oil. - thoughts?
 
Well I better not tell my buddy we need to pull the prop again:).

Is leaking only airborne - or I assume higher MAP commonly associated with a prop seal leak?

We used a single piece seal - I cleaned like crazy to include with a pick - the grove was clean and used emery cloth on the shaft - it was clean.

We then used the prescribed DOW 737 sealant.

We did not use the prescribed tool to stretch it, but heated the seal and it pulled over the prop hub fairly easily - inspecting it prior to installing the spring and putting it in place it appeared undamaged.

Prior to pulling the prop again - I might try putting some foot powder on the visible portion of the case below the prop seal to see if I get any oil. - thoughts?

Looks like you have done good. However, I had one mechanic tell me to heat the seal in hot oil. That destroyed the seal. Might not be your case.

I noticed oil on top of the intake plenum and replacing the seal fixed it.

I don't know about foot powder but the spray powder(?) designed for detecting leaks and sold at aircraft shops stay on the surface for a long time.
 
I heated that seal in hot water and used the proper tool. Went on easy. Heard of the hot oil trick but as afraid the glue would not bond. If your seal was leaking, most likely it left oil all over the engine and that will drip off for a while unless you can clean it off.
 
hot water

We used hot water as well - let it sit at a low boil for about 20 minutes or so.

I would hate to pull the prop again - but really want to solve this - my other wonder is do I need to go with an over sized seal - not sure how I tell? Reading it sounds like that is a major - crack the case type of event.
 
Oil leak

Problem is these are air cooled engines. The air can massively effect were the oil goes once it leaks out. I replaced 2 good crank seals trying to fix a leak. Drops of oil on front bottom cowl and running along case split on bottom. Eventually found the leak to be the vacuum drive seal. Oil would leak from the vacuum drive seal, then pass forward past the baffles along the case split and run alll the way forward to the front seal. Then after shutdown drip on the cowl and run back along case split bottom. I hade tryed the talk trick, pressure test. Etc... Finally found it just by chance. Replaced the vacuum drive seal and it never leaked agin. Fought this helps but just an old a&p’s story. Lesson learned oucums Razor doesn’t aloes apply.
 
RV10 oil leak

I’ve been adding a quart every 10 hours and ignoring oil on the belly, plus very small pool after sitting more than two weeks. Any thoughts on my inaction? New 540 890 Hobbs
 
UV Dye

We tried the UV dye this weekend with a good result - I had a significant leak from one of the push rod covers on my #6 cylinder. The leak was the first push rod aft of the oil fill/dip stick which probably helped to mask the source. But under the UV we could see it was a pretty significant leak around the green push rod cover gasket. We replaced the gasket and added some tite seal. I haven't had a chance to run it but hope to get up there one night this week and I will share the results with everyone.

Thanks once again to everyone for the great suggestions - I think "we" may have solved this . . . knock on wood.
 
Fixed

Just wanted to follow up and thank everyone - especially my FSO RV10 stablemate for all the help. The Oil leaks on 95VT are officially fixed.

Yes you will note the plural. I had a leak from the inboard-forward push rod cover on #6, from the magneto cover plate, and a very slight leak from the oil filter adapter and one of the case through bolts - the one that has the forward hanger integrated. A replacement seal, some tightening and a generous application of tank sealant seems to have done the trick.

I have another 10 hours on this oil until it is time for a change so I will continue to peak under the cowling after dark to see if the UV dyed oil shows up anywhere else but it looks good. [vigorous knock on wood]

Thanks again for all the help.
 
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