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Pesky engine oil leaks

Paul Eastham

Paul Eastham

Well Known Member
Hey gang,
Just uncowled for oil change #3 on my Aerosport O-320 and found several new oil leaks that have appeared between 40 and 65 hours. I'm curious if anyone has had experience with leaks in these spots, and are leaks like these inevitable on threaded fittings somewhere on the engine? All the rental birds I ever flew sure seemed to have em...

#1 seems to be leaking from the threads of a stud where it emerges from a nut. Sad to say I do not know what this thing is for -- forward upper left side of crankcase. Torque seal still intact from aerosport, just now I put a 10" wrench on it and couldn't tighten it further.

2130446680_65d24ec77c.jpg


On the plus side, I can keep an eye on this one without decowling. Looks like it has leaked about 15 drops of oil. Made a nice mess against the back baffle wall.

#2 is the oil quickdrain, leaking around the threads. Was installed with ez-turn, and cranked it in as hard as I could with a 1-foot wrench. Not enough?

2130446390_a6d6d4d2b1.jpg
 
I'm sure you will get some good info quickly but before you do.... STOP wrenching stuff as tight as you can. You are going to strip, break, or otherwise cause yourself more problems unless you know for sure how much force can be applied. This is not the case where.... "when in doubt, get a bigger wrench".

I'll stop now and let the gear heads chime in.
 
In my defense, I do believe I looked up the allowed torque for such a large NPT (the oil drain) and decided that it was more than I could apply -- since it was off the scale of a torque wrench that I'm just barely able to max out.

On the stud, #1, it was already torqued more than I could manage with standard length wrenches. I didn't budge it.
 
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Sometimes the places where you think the oil is leaking is not the place it is actually leaking. There is a lot of air movement in there and the oil could be coming from somewhere else and just collecting where you see it. The oil leak at the drain plug is probably weeping a bit. Call Bart and ask him, he'll be more than happy to help you.
 
What kinda of thread sealing are you using? We all know teflon tape is a nono. How about the TFE liquid paste plumbers use?
 
Regarding the quick drain, mine spits a little through the valve. After oil changes, I stuff a rolled up paper towel up inside to remove oil below the valve. I see oil in the threads above, but I've convinced myself that vibration causes some leakage through the quick drain valve. I always have a few drops generally below this area. When the cowl is off, I'll stuff another paper towel inside, and there is always oil. It is not quite a big enough nuisance to do anything about.
 
AlexPeterson said:
Regarding the quick drain, mine spits a little through the valve. After oil changes, I stuff a rolled up paper towel up inside to remove oil below the valve. I see oil in the threads above, but I've convinced myself that vibration causes some leakage through the quick drain valve. I always have a few drops generally below this area. When the cowl is off, I'll stuff another paper towel inside, and there is always oil. It is not quite a big enough nuisance to do anything about.
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Thanks Alex, you might be right about that. I'll use that technique to monitor it further.
 
Titeseal

I used medium weight Titeseal on all fuel, oil, and brake NPT fittings on my plane. I also amd fighting a few tiny oil leaks on my Aerosport O-360 but nothing with assembled with Titeseal has ever leaked. Aircraft Spruce has it as well as some auto part stores.

Paul Danclovic
Carver MN / Albuquerque NM
RV-8A at the paint shop
 
Paul, in your first photo, there appears to be a crack in the casting where the cylinder base stud is.

Perhaps it is just something in the photo------sure hope so, as the crankcase is a bit expensive------but if that is indeed a crack, that may be the source of your oil leak.

Or, am I just seeing things????
 
Mike S said:
Paul, in your first photo, there appears to be a crack in the casting where the cylinder base stud is.

Perhaps it is just something in the photo------sure hope so, as the crankcase is a bit expensive------but if that is indeed a crack, that may be the source of your oil leak.

Or, am I just seeing things????
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I see the same thing, 200 degrees from the #2, its either a crack or a bit of casting flash.
 
#1 seems to be leaking from the threads of a stud where it emerges from a nut. Sad to say I do not know what this thing is for -- forward upper left side of crankcase. Torque seal still intact from aerosport, just now I put a 10" wrench on it and couldn't tighten it further.
Click to expand...

Paul, I had the same leak at the case stud on my O-320. I removed the nut and spacer, applied RTV, reinstalled the nut and the leak dried up. One A&P told me this is common and sometimes the spacer is machined for an o-ring in order to seal the nut.

However........please call Bart on this one. There is a possibility he may not want you to release the torque on that stud since it is a case through stud.
 
Paul,

If what looks like a crack really is a crack, I would expect a LOT more oil than you're getting.

I'm not sure about Lycomings, but Continentals have o-rings on the through studs as shown here:
image011.jpg


It sometimes can take a few hours of running for omission of one of these o-rings to cause a leak. I have heard of a few folks getting away with putting sealer and/or an o-ring under the washer on the outside, but as little time as you say is on the engine, I'd first refer the problem back to the builder.
 
Guys,
Thanks for the sharp eyes on that "crack". I zoomed in on the original photo and it sure did look like a crack. I rushed down to the airport fearing the worst, but found a small casting defect (basically a small "divot") that is clearly not a crack. Something about the lighting in the photo made it look that way.

Relieved, I put a longer wrench on the nut and still could not budge it, so I left it alone. I found the oil drain to be a bit loose and snugged that up. After a short half-hour test flight the oil sump is leak-free but the through-bolt has weeped at least two drops of oil, both between the nut and the spacer and on the outer face of the nut.

I will consult Bart at Aerosport about this leak and will report back. Thanks for the info about sealing that thing.

Paul
 
Paul Eastham said:
Guys,
Thanks for the sharp eyes on that "crack". I zoomed in on the original photo and it sure did look like a crack. I rushed down to the airport fearing the worst, but found a small casting defect (basically a small "divot") that is clearly not a crack. Something about the lighting in the photo made it look that way.

Paul
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Paul, glad it was not a crack. It sure does look like one in your photo, though.

Sorry to have gotten your heart rate up.
 
Post test-flight, here is a photo of the stud still leaking, and the casting defect that looked like a crack in the previous photo...

IMG_4883.JPG
 
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Follow up: Bart at Aerosport recommended to remove the nut and spacer and retorque with red RTV in between and on the threads. No leaks after a few flights.

But, as soon as I got that one fixed, another one sprung up. One of the cylinder hold-down nuts on the other side of the engine started leaking the same way (out of the threads on the outer side of the nut). Fairly large amount of oil leaked during a short flight. I guess I'll pester Bart again, but does anyone else have experience with this?
 
Paul Eastham said:
But, as soon as I got that one fixed, another one sprung up. One of the cylinder hold-down nuts on the other side of the engine started leaking the same way (out of the threads on the outer side of the nut). Fairly large amount of oil leaked during a short flight. I guess I'll pester Bart again, but does anyone else have experience with this?
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Bummer - I wonder if the o-rings were left off accidentally when your engine was built up. I have 200 hrs on my Aerosport O-360 - no leaks.
 
Another item that can cause your engine to spit oil is the location of your crankcase vent. I moved mine downstream of the cowl opening and all my little weepers stopped cold. Seems that the pressure inside the cowl was pressurizing the vent line and consequently, the crankcase. This was pushing oil out from inside the crankcase. My belly is much cleaner now.
 
Paul Eastham said:
Follow up: Bart at Aerosport recommended to remove the nut and spacer and retorque with red RTV in between and on the threads. No leaks after a few flights.

But, as soon as I got that one fixed, another one sprung up. One of the cylinder hold-down nuts on the other side of the engine started leaking the same way (out of the threads on the outer side of the nut). Fairly large amount of oil leaked during a short flight. I guess I'll pester Bart again, but does anyone else have experience with this?
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At about 45 hours on my TMX IO-360, I got a small oil leak around the base of one of the cylinders and on two of the hold-down nuts for the same cylinder. I had no leaks at all until that point. Mattituck directed me to have the cylinder pulled (at their expense -- still under warranty) to replace the O-ring at the cylinder base. We found that the old O-ring had a slight twist in it, which could have caused the leak.

A new engine shouldn't be leaking. My advice is to fix all the pesky stuff now while the engine manufacturer will still work with you. If you ignore it, sooner or later you're going to wish you had dealt with it.
 
Not all engines have the O-rings

kevinh said:
Bummer - I wonder if the o-rings were left off accidentally when your engine was built up. I have 200 hrs on my Aerosport O-360 - no leaks.
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My IO-360 did not have O-rings around all the studs. Since my engine is in the shop, I asked ECI to modify it and add the o-ring grooves for the studs.

I had numerous "irritation" leaks around my studs and cylinder bolts. After removing, cleaning (with brake cleaner), adding RTV and re-torquing, 99% of them were gone. I still had one I never found, but it was very small.

Just FYI,
 
f1rocket said:
Another item that can cause your engine to spit oil is the location of your crankcase vent. I moved mine downstream of the cowl opening and all my little weepers stopped cold. Seems that the pressure inside the cowl was pressurizing the vent line and consequently, the crankcase. This was pushing oil out from inside the crankcase. My belly is much cleaner now.
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So I'm a bit late to the thread here, but is there any chance you might have a pic of your new vent installation? My O-360 tends to use a quart every 7-8 hours or so, plus I have a couple little weeper leaks that have me baffled; I can't find exactly where they are! They seep just enough to annoy me... makes me wonder if my standard Vans breather tube installation (inside the cowl, right above the exhaust stack) might be causing it. So, extending the vent tube downstream from the cowling doesn't create suction to pull more oil out?

Thanks!
 
Sorry but no picture. Here's what I did though. I too, had my vent line terminating just above the exhaust inside the cowling. I took off the tubing on the end of the hose and replaced it with one that bends down around the engine mount and points out the back of the cowl opening, next to the exhaust.

This is a mod that a fellow Rocket builder, Tom Martin experimented with. It works great. I consider this one of the best mods I've made to my airplane since I started flying it.
 
Yep, I'd read Tom's posts about this subject as well and it looks like it'd be worth a try on my machine. Would be nice to have a dry engine and belly...

Thanks Randy!
 
Vent Tube

Randy, My engine is running like John's also. Is the vent line pointing down or aft? I'm going to redo my vent line this week and still don't get it yet. Did you cut the end at an angle or just straight?
 
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