Oil leak -- how bad is this?

[jaylw314]

So I posted earlier that my IA retired and is closing his shop.  Naturally, I noticed the next couple flights that my oil usage seemed to go up (about a quart after 3-4 hours) and that I was getting more oil dripping onto the nose gear when I come back to the plane.  Normally there's about a teaspoon's worth of oil on the nose gear, but this time it looked more like a tablespoon.  The motor has always been pretty oily in bottom half of the cowling, but I only go through a quart every 8-10 hours normally so I never thought much of it.

I took the cowling off and noticed some oil seepage around the upper half of cylinder #3 that I'm pretty sure is new.  I wiped around what I assume is the oil pressure relief valve and couldn't find any oil on the valve itself, which I assumed would be the more likely source.  The right lower half of the motor is all pretty oily now, so it's pretty tough to see anything obvious, but it's definitely worse than the left side.

If this is the source, how could it suddenly increase like this?

 

Edited May 27, 2023 by jaylw314

[MB65E]

All normal to me. Case Studs and through bolts leak after time. Need to pull a cylinder off to fix it properly. I’d leave it alone. 
-Matt

[MikeOH]

I don't think that minor seepage is the source of your 1 qt in 4 hours vs. 8 hours.  Something else is leaking, IMHO.

[PT20J]

Leaks are not usually the cause of high oil consumption. I quart of oil is a HUGE leak. 

[PT20J]

BTW, your IA closing his shop but I know a couple of good mechanics that did the same thing but will still work part time for a few customers. It keeps their hand in it and provides beer money. If you have a good relationship with him, I’d make him an offer. He may be open to an arrangement if you offer to pay him him well and do the grunt work yourself.

[jaylw314]

2 hours ago, PT20J said:

BTW, your IA closing his shop but I know a couple of good mechanics that did the same thing but will still work part time for a few customers. It keeps their hand in it and provides beer money. If you have a good relationship with him, I’d make him an offer. He may be open to an arrangement if you offer to pay him him well and do the grunt work yourself.

I am sadly pretty sure there are some serious family health issues involved so I am guessing not, but I was going to call him next week anyway to see if he had people to suggest. 

FWIW, I forgot to feel inside the exhaust, but it looked clean.  I'll double check that tomorrow and keep looking elsewhere, I just had to quit today because I was getting high on mineral spirits 

 

[A64Pilot]

On 5/27/2023 at 6:40 PM, PT20J said:

Leaks are not usually the cause of high oil consumption. I quart of oil is a HUGE leak. 

Take a teaspoon of oil heat it up until it’s as thin as water, add in over 100 MPH of wind and it will cover the entire belly.

[McMooney]

Mine was the oil cooler, almost impossible to find.

 

took it to a radiator/heat exchanger repair shop,  they applied 50 to 75psi of air to the inlet before the crack in the cooler showed itself

[jaylw314]

1 hour ago, A64Pilot said:

Take a teaspoon of oil heat it up until it’s as thin as water, add in over 100 MPH of wind and it will cover the entire belly.

I do get a pretty oily belly, but it's always been that way and tough to tell if it's changed

1 hour ago, McMooney said:

Mine was the oil cooler, almost impossible to find.

 

took it to a radiator/heat exchanger repair shop,  they applied 50 to 75psi of air to the inlet before the crack in the cooler showed itself

Luckily, it's pretty clear looking on the cowling bottom that there's no oil dripping down the left side of the cowl at all, but there's a small oil stain on the right side.

In retrospect, when I saw the drop in oil level, it was at 8 qt after sitting for a few weeks, and at 7.5 qt after only a few days.  It's hard to imagine, though, that all the oil will not return to the sump within 24 hours

[Bolter]

52 minutes ago, jaylw314 said:

I do get a pretty oily belly, but it's always been that way and tough to tell if it's changed

Luckily, it's pretty clear looking on the cowling bottom that there's no oil dripping down the left side of the cowl at all, but there's a small oil stain on the right side.

In retrospect, when I saw the drop in oil level, it was at 8 qt after sitting for a few weeks, and at 7.5 qt after only a few days.  It's hard to imagine, though, that all the oil will not return to the sump within 24 hours

It is common for the first few quarts to go faster when filled to 8 quarts.  You will find many threads about keeping the IO-360 at 6 quarts.  That was consistent with my own experience with my J.  You need to track consumption over many hours, for as long as it is staying around 6 quarts.  

[jaylw314]

44 minutes ago, Bolter said:

It is common for the first few quarts to go faster when filled to 8 quarts.  You will find many threads about keeping the IO-360 at 6 quarts.  That was consistent with my own experience with my J.  You need to track consumption over many hours, for as long as it is staying around 6 quarts.  

Yeah, I usually tell the shop to only put in 7 quarts but I forgot last time.  That should result in oil coming out the breather and onto the belly, though, not onto the nose gear.  Admittedly, I flew so little for most of the last 4 months that my impression of sudden 'change' in oil consumption may not be accurate 

[Yetti]

What you are looking for is a drip on something.  Then follow it upstream from there.   Just go ahead and tighten up all the clamps on the drainback tubes.    Mine are still the thumb ones.   I can get to them with a 1/2 socket.   1/4 drive ratchet sometimes a swivel head

[jaylw314]

16 hours ago, Yetti said:

What you are looking for is a drip on something.  Then follow it upstream from there.   Just go ahead and tighten up all the clamps on the drainback tubes.    Mine are still the thumb ones.   I can get to them with a 1/2 socket.   1/4 drive ratchet sometimes a swivel head

Yes, I was trying to follow it, but the bottom half was oily enough there was nothing obvious.  That's when I gassed myself spraying things down with mineral spirits .  I was going to come back and test run the motor after it dried, but I started feeling kind of wonky.  I'll go back and do that this weekend

By drainback tubes I assume you're talking about the breather tube?  That runs down the left side, and the left side was clean

Edited May 31, 2023 by jaylw314

[EricJ]

14 minutes ago, jaylw314 said:

By drainback tubes I assume you're talking about the breather tube? 

There is a drainback tube from each cylinder head to the sump.    This is how oil returns from the heads to the sump.    They are bent tubing with fittings on the bottom-side of each cylinder head and run under the cylinder to the sump.   On most airplanes there is a short segment of rubber hose near the sump to dampen vibration so that the tubes don't crack.   These tubes are common leak points for lots of reasons, including getting breached by wear-through rubbing from baffles or hoses or wires or just random stuff that got misrouted and not secured or checked.    A hole wears into the tube and it starts leaking.   The joints at the rubber hoses are also common leak points if they get loose.   They are usually secured with hose clamps, sometimes with the easy flat handles for hand-tightening, sometimes with the usual screw/nut tightener.

They're not too hard to inspect because they're pretty easy to see with the cowl off.    Often if one is leaking there'll be an oil drop hanging off of it somewhere.   If there are signs of leaking around them the hose clamps can be snugged up fairly easily.

[jaylw314]

2 minutes ago, EricJ said:

There is a drainback tube from each cylinder head to the sump.    This is how oil returns from the heads to the sump.    They are bent tubing with fittings on the bottom-side of each cylinder head and run under the cylinder to the sump.   On most airplanes there is a short segment of rubber hose near the sump to dampen vibration so that the tubes don't crack.   These tubes are common leak points for lots of reasons, including getting breached by wear-through rubbing from baffles or hoses or wires or just random stuff that got misrouted and not secured or checked.    A hole wears into the tube and it starts leaking.   The joints at the rubber hoses are also common leak points if they get loose.   They are usually secured with hose clamps, sometimes with the easy flat handles for hand-tightening, sometimes with the usual screw/nut tightener.

They're not too hard to inspect because they're pretty easy to see with the cowl off.    Often if one is leaking there'll be an oil drop hanging off of it somewhere.   If there are signs of leaking around them the hose clamps can be snugged up fairly easily.

Cool beans, I'll be on the lookout for that, thanks!

[Joe Larussa]

Get the proper dye to put in the crankcase and a black light. Makes it easier to find the leak.

[jaylw314]

Just to follow up on this:

I cleaned off the bottom half as best I could, and let the mineral spirits evaporate overnight before test running the motor a couple times.  When I went to check the oil level today, lo and behold, it was about a quart higher than last week.  If that's the case, then my oil consumption is actually about normal??  I recall last time when I checked the plane had been sitting about a week as well, and was down to about 6.2, now it's back up to about 7.0 quarts.  I'll be keeping a close eye on that, obviously.

However, after test running and doing a few circuits, there is definitely a new oil drip from the firewall after shutdown.  I'm not noticing the belly any dirtier, and the exhaust is dry inside, but it looks like it's coming from the accessory area and dripping down.  The magnetos look dry, as does the oil filter and oil cooler connection.  The drainback tubes stayed dry.  The fuel pump had oil on it, but its mounting pad looked dry.  I couldn't tell if it was coming from the fuel pump or something above it.

Anyway, I'll have to figure out who to take it in to to narrow down the leak.

 

[A64Pilot]

Clean it again and run it up until you find it.

For spot cleaning a spray bottle with isopropanol alcohol and paper towels work well. 90% alcohol evaporates pretty quick

It is possible for a fuel pump to leak oil from its mounting gasket.

My IO-360 Lyc any oil higher than 6 is pretty quickly blown out, so if I try to keep it at 7 my oil consumption is much higher than if I keep it at 6.

[Skates97]

On 6/1/2023 at 7:19 AM, Joe Larussa said:

Get the proper dye to put in the crankcase and a black light. Makes it easier to find the leak.

Clean the engine, put the dye in, take it around the pattern once and then put a black light on it. If you fly it more than once around the pattern it will blow all over and you wont' be able to track it down. We were chasing a leak for a bit until my AP/IA had me go this route. He put a black light on and it was obvious that it was the quick drain for the oil that had a very slight leak. Never had any drips on the wheel, but it was coming up out of the top/front of the cowl and back towards the windshield.