Oil leak somewhere near the carb

[NunavutPA-12]

I thought I was losing oil from the hose sections on the oil return lines. Turns out those leaks are minor. After cleaning the lower cowling, it's obvious that the oil is leaking somewhere around the carburetor.
I lose about a quart an hour so it really need fixing.
No leak when sitting, only when the engine is running. Bolts all seem tight. O320B2B.
Suggestions?

 

[skywagon8a]

There is no place around the carburetor which would leak with the engine running and not leak when the engine is stopped. Thoroughly clean the bottom of the engine with some solvent. Fly the plane once around the traffic pattern and look for the leak. Look inside the ring gear behind the alternator belt groove. If the nose seal is leaking that will be wet along with the seam of the case just behind it.

Sometimes, particularly in cold regions like yours if there is no vent in the crankcase breather tube (whistle opening) in a warm location, the breather tube can freeze over causing a pressure build up inside the crankcase. This condition can push out a nose seal if the adhesive has loosened. This will spit out oil sometime in quantity. If the adhesive is weak the seal can slide out on it's own.

Alternatively check the clamps and connector hoses for the rocker box drain tubes where they enter the crankcase. Maybe one of the connector hoses is broken? Check these first.

 

[dgapilot]

I’ve seen leaks at the filler tube quite often. Best way to find a leak is to clean the engine very good, dry it, and put baby powder all over any area of suspected leaks. Run for 5 minutes and check. Repeat until you have signs of oil in the baby powder. Once the baby powder shows oil, you found at least one leak!

Have you looked at your oil cooler? If you have the nose cooler, and it’s leaking, it could be blowing back on the engine.


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[mike mcs repair]

Dga hit the baby powder trick. Also look look up top at Push rod housings... just because it drips off at the bottom doesn’t mean that’s where it came from. Also check cylinder base nuts


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[skywagon8a]

I’ve seen leaks at the filler tube quite often.

Not at the rate of a quart an hour.

 

[Steve Pierce]

The bottom of the crankcase halves forward of the carburetor is notorious for leaking. Removed bolts, clean, put Aviation Permatex in holes and on bolts, retorque and hold your mouth just right.

 

[dgapilot]

I thought I was losing oil from the hose sections on the oil return lines. Turns out those leaks are minor. After cleaning the lower cowling, it's obvious that the oil is leaking somewhere around the carburetor.
I lose about a quart an hour so it really need fixing.
No leak when sitting, only when the engine is running. Bolts all seem tight. O320B2B.
Suggestions?

When I had my Howard, the R985 wouldn’t even go through a quart an hour!


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[cubpilot2]

I've seen crankshaft nose seals do weird things depending on the airflow through the cowling.
Friend of mine had what he thought was for sure an oil cooler leak but turned out to be the seal.
Perhaps the airflow is drifting oil to the front of the sump....

The baby powder trick works awesome. I've used it for years.

 

[supercrow]

I suspect like Steve that the case is fretting and leaking at the case split. Around the starter mount is a common place for a crack and leak too.

 

[NunavutPA-12]

Here's some photos. The sides of the lower crankcase and the sump are fairly dry. There is some oil on the lower left side of the engine mount. I tightened up all the case-half bolts and those holding the sump in place. Mag bolts and accessory case bolts are all tight. I'm now losing about 1/2 qt. in a 1.5 hour flight. Leaks only when running.

 

[don d]

Big oil leak!! Flying along 10 miles South Cascade, Idaho this morning, minding my own business.
Glanced over at gauges and 0 oil pressure! Trottl3d way back and headed for Cascade. Copper oil pressure line broke. Didn't have much oil when I got to Cascade. Mike Arnold was there and fixed me up. Restector goes in that line.

 

[mike mcs repair]

Here's some photos. The sides of the lower crankcase and the sump are fairly dry. There is some oil on the lower left side of the engine mount. I tightened up all the case-half bolts and those holding the sump in place. Mag bolts and accessory case bolts are all tight. I'm now losing about 1/2 qt. in a 1.5 hour flight. Leaks only when running.
View attachment 43871
View attachment 43872
View attachment 43873

Need more pictures. Oil screen? Housing ears bent and or cracked?


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[NunavutPA-12]

I have noticed a decline in the leak recently. Down to 1/2 qt. in a 1.5 hour flight, and about 1/4 qt. if I keep the oil level at 5-1/2 qt.

 

[skywagon8a]

Larry, what is the condition of the gasket where the dip stick tube screws into the case? Those gaskets are generally just a thin paper materiel which can shrink causing leaks. A high oil level could work it's way out there getting blown forward fooling you into looking elsewhere. The paper gasket could be replaced with an "O" ring. It's not uncommon to find these tubes loose.

 

[NunavutPA-12]

I'll check that later today. Thanks Pete. The dipstick tube and the quick-drain fitting are two things I haven't checked for tightness yet.

 

[LMartin]

I'm pretty sure I have oil leaking from the lower, forward crankcase seam at and/or just in front of the most forward lower case bolt. It's messy! I originally thought it must be a crankshaft seal, but it's not coming from there. I flew it home from Coeur d'Alene (6 hours) and added a quart. We did several cycles of cleaning the engine and then short run (otherwise its all over)...like a minute or 2 at idle...and found it seeping there. Also, some of the red case glue was coming out. I checked the forward bolt, I should have spent more time finding it in Coeur d'Alene) and it was very loose. The person that installed the forward oil cooler bracket must have forgotten to tighten and torque it. We did torque it, but the seal is breached. So now I'm thinking Proseal/Chemseal. Any of you that are good at this, would you please give me clear and detailed instructions? I don't want to split the case. I have cleaned it well with acetone, and scuffed with scotch brite. I have a handy tube in the fridge next to my supper waiting for me to get brave enough to mix it. Do I apply a couple layers? Do I try to lay a thin bead in the gap, then another layer across the seam edges? Should I stick trim tape at the edges to keep the edges straight? How thick should I apply it? Anything else? Thank you. I can't find anything about it on YouTube. I have worked with Proseal a little to patch up floats. It's great stuff.

 

[akmarty]

After you clean up, run a few minutes and grab a black light and look for the new oil. It will glow.

https://www.lowes.com/pd/Kobalt-Blacklight-51-Uv-LED-Flashlight-Aa-Battery-Included/5013922183

 

[LMartin]

After you clean up, run a few minutes and grab a black light and look for the new oil. It will glow.

https://www.lowes.com/pd/Kobalt-Blacklight-51-Uv-LED-Flashlight-Aa-Battery-Included/5013922183

Oh if Lowe's has them, I bet home depot does too. I'll look tomorrow.

 

[akmarty]

The thing I like about the Lowe’s version is how short it is. It will fit around the back of my engine whereas a lot of other black lights are too long.

 

[Steve Pierce]

Can you tell it is the seam and not a bolt hole? Doesn't take much, just a skin. I have seen some of the cylinder hold down studs that thread into the case, not the through studs, leak profusely and look like the case half. Also the 1/4" case flange bolts.

 

[cubpilot2]

If no black light is available then clean the area again and dust it with any type of “foot powder” talcum or baby powder. Run for a few minutes. The oil will leave a nice trail in the powder film showing the source.

 

[CubCruiser]

If you mix the baby powder with rubbing alcohol, it can be applied has a spray from a squirt bottle. It will dry relatively quickly and adhere to surface.

 

[Dog]

We use -- The right stuff a permatex product I believe.

Hands down the best sealer for that type of aplication.

This has cut down our PRC use quite a bit.

 

[larrym]

I have used with success, as does the engine shop here Loctite 290 which will wick into the seem. Put a vacuum on the breather to suck it into the seem. apply several times as needed. The engine shop uses that technique on all the engines as they see fit during the test runs.

 

[kase]

Dye in the oil on a small Continental

 

[LMartin]

Thank you! I didn’t realize I had more help after the first. The PRC helped a lot, over 50% less in a 5 min ground run. Still messy with oil down the right side starter nuts and on to the oil cooler though.We started suspecting the oil cooler (and found a very loose jam nut) so tightened, cleaned thoroughly again and got a black light. Nothing shows at all on the oil cooler now. It’s not gone, but down to no dripping at all, just a seep coming from way up the case behind the prop where I can’t get a mirror or camera. Our original thought was crankshaft seal and we’re starting to think maybe it does have a small seep, but I’m also thinking that it may have been just some thing I missed in the seam, because it’s slow down so much. After the last two runs it’s dry for about 5 minutes, then it starts to show at the front seam looking through the right (of the airplane) nose cowl hole. I’ll attach a picture just in case any of you has any immediate thoughts on it. Otherwise I’m probably gonna leave the prop on for a week and fly because it’s just a little messy, and maybe order a crankshaft seal to install later.

 

[hotrod180]

I had a 320-E2A in my old C150/150TD.
It developed a leaky crank seal-- looking through the logbooks,
turns out it'd had that seal replaced several times.
I installed a new seal, using non-drying permatex (unfortunately I don't recall the p/n).
Ran it for another 500 hours or so before selling the plane-- no more leaks.

 

[LMartin]

I am so hopefully awaiting a test flight tomorrow afternoon! In desperation we decided to replace the crankshaft seal, and in trying to remove the old one discovered that a seal had never been installed…too many injuns and too many years. I will remember to check for that now!