Oil on windscreen

JBrown243

JBrown243

Pre-takeoff checklist
Joined
Sep 6, 2012
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201
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San Jose, CA
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Display name:
Jason
ok, so the past couple of flights im finding oil on my windscreen. It looks like it might be coming from the prop governor because it is a little damp but its not an obvious leak. there are no drips.

the oil seems to somehow be sucked out from the front of the cowling and then pushed back along the cowl and onto the windscreen.

anyone have anything similar happen?
 
bartmc said:
No, and it wouldn't happen but once.

Sounds like prop issues.

Time for a pro.
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Before condemning a very expensive prop, I suggest looking at the prop/crank oring and the crankcase nose seal.

I had 177B doing the same thing. It was $0.25 oring that seals the prop to the crank. No prop work needed in this case, just a PiTA to remove the prop. Think about a new alternator belt while its off.
 
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Just had the same thing happen with mine....light spray on the windshield. I haven't pulled the spinner yet but I'm guessing a prop seal is leaking. Might be a good idea to have someone who knows whats going on to look at yours. It could be a simple thing or it could be bad. Check it out first.

Frank
 
What kind of airplane is that? I've not had oil on the windshield since I got rid of my old Hartzell bladder prop.
 
bnt83 said:
Before condemning a very expensive prop, I suggest looking at the prop/crank oring and the crankcase nose seal.

I had 177B doing the same thing. It was $0.25 oring that seals the prop to the crank. No prop work needed in this case, just a PiTA to remove the prop. Think about a new alternator belt while its off.
Click to expand...
:yeahthat:
 
JBrown243 said:
ok, so the past couple of flights im finding oil on my windscreen. It looks like it might be coming from the prop governor because it is a little damp but its not an obvious leak. there are no drips.

the oil seems to somehow be sucked out from the front of the cowling and then pushed back along the cowl and onto the windscreen.

anyone have anything similar happen?
Click to expand...

You must be flying a TCM engine, because the Lycoming prop governors are on the accessory case.

TCM governors are on the left side opposite of the oil cooler both of which could be your source of the leak.

1 or 2 drops per hour will make a big mess on the wind screen and are very difficult to locate.
 
bnt83 said:
Before condemning a very expensive prop, I suggest looking at the prop/crank oring and the crankcase nose seal.

I had 177B doing the same thing. It was $0.25 oring that seals the prop to the crank. No prop work needed in this case, just a PiTA to remove the prop. Think about a new alternator belt while its off.
Click to expand...
I wouldn't think having a pro look at it would be condemning the prop. He would just make sure you are fixing the right problem. With a problem like this, you don't want to guess.
 
Tom-D said:
You must be flying a TCM engine, because the Lycoming prop governors are on the accessory case.

TCM governors are on the left side opposite of the oil cooler both of which could be your source of the leak.

1 or 2 drops per hour will make a big mess on the wind screen and are very difficult to locate.
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Depends, I think he has a Comanche and 540s have front mount governors.

I would be looking at the nose seal, the blade seals and the crank/prop seal
 
JOhnH said:
I wouldn't think having a pro look at it would be condemning the prop. He would just make sure you are fixing the right problem. With a problem like this, you don't want to guess.
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Please read what I responded to:

bartmc said:
No, and it wouldn't happen but once.

Sounds like prop issues.

Time for a prop.
Click to expand...

If you tell a shop you want the prop overhauled, due to a forum diagnosis, they won't even bat an eye or look into the problem that wasn't mentioned.
 
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bartmc said:
Doesn't seem to be what I wrote. Forum diagnosis was "sounds like a prop issue" because to me, it "sounds like a prop issue". I didn't suggest he take it to shop and say "overhaul it"

I can't come up a scenario where "flying a couple of times" with oil accumulating on the windscreen is a great idea (Do we need a placard for that?)

I also can't come up with a scenario where I'm getting oil on my windscreen and my first reaction isn't to land ASAP and hand it over to a professional for diagnosis and treatment.
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So you wouldn't fly a long cross country at night (1,200 NM) with an unknown oil leak that continually spews oil on the windshield?
 
bnt83 said:
So you wouldn't fly a long cross country at night (1,200 NM) with an unknown oil leak that continually spews oil on the windshield?
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You need to go back for Remedial English 101. Learn the difference between "a little damp" and "continually spews".

As Tom so gracefully puts it, two or three drops of oil an hour makes a bit of a mess. That's "drops", not "spews".

Jim
 
yeah i had the shop i take my plane to take off the governor and inspect it and they said they didn't see any leaks and asked if i wanted to send it out to have it overhauled. the overhaul is very expensive and the plane would be down for weeks, and it might not even be the problem. ill post pics later.

as far as how much oil is coming out on the windscreen. ive noticed this the past 2 flights. the first time i thought it might be from my not tightening the oil cap on tight enough. the second time i started to worry. the second flight was a 700nm cross country and the amount on the windscreen was a very fine mist. with a small streak coming from the front cowl. less than a 1/2 oz of oil total.

I just don't want to throw money at something that might not be the problem and wanted some input from others who might of had the some problem or something similar. I don't think its coming from the prop hub because the blades are dry. I'll ask the shop check the oring that seals the prop to the crank next.
 
I've flown a few CS prop planes that get a little of that, both piston and turbine.

How many hours before you notice oil on the windshield?
 
most of the time its not a bad prop - the seal was not installed completely correctly and it ends up being a seal that rolled a little in the channel allowing oil. An hour of labor and a seal and its all fixed- assumed they did not roll the seal again when they put the prop back on again - but at least that hour is not on you. . . .
 
JBrown243 said:
yeah i had the shop i take my plane to take off the governor and inspect it and they said they didn't see any leaks and asked if i wanted to send it out to have it overhauled. the overhaul is very expensive and the plane would be down for weeks, and it might not even be the problem. ill post pics later.

as far as how much oil is coming out on the windscreen. ive noticed this the past 2 flights. the first time i thought it might be from my not tightening the oil cap on tight enough. the second time i started to worry. the second flight was a 700nm cross country and the amount on the windscreen was a very fine mist. with a small streak coming from the front cowl. less than a 1/2 oz of oil total.

I just don't want to throw money at something that might not be the problem and wanted some input from others who might of had the some problem or something similar. I don't think its coming from the prop hub because the blades are dry. I'll ask the shop check the oring that seals the prop to the crank next.
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Rain can really mess up the forward visability with a leak like you have.

If its the crankcase nose seal you will find an oily residue on the back side of the starter ring gear and probably flung off it onto the cowling also.
 
bnt83 said:
Rain can really mess up the forward visability with a leak like you have.

If its the crankcase nose seal you will find an oily residue on the back side of the starter ring gear and probably flung off it onto the cowling also.
Click to expand...

And a prop/crank seal will lube the front of the flywheel
 
No matter how much oil my props and governors are leaking, I have never gotten oil on my windscreen. Oh wait...

And many Lycomings have the prop governor located in front of the #2 cylinder.
 
When this symptom happened to me, it was a hairline crack in the top of the engine case.

Really, pay for someone to do diagnostics - shotgunning it will get very expensive, very quickly.
 
wsuffa said:
When this symptom happened to me, it was a hairline crack in the top of the engine case.

Really, pay for someone to do diagnostics - shotgunning it will get very expensive, very quickly.
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Its seems like some owners on here love to pretend that Lycomings are bullet proof, however I know of at least 6 case crack storys on O-320 that was freshly rebuilt, and O-360 & IO360.
 
We had a tiny oil leak last year. Pros said "deep cycle the prop for the next five flights". Leak stopped. Mentioned it again to pros at Annual. Found nothing. It doesn't take much to make a huge mess.
 
comanchepilot said:
most of the time its not a bad prop - the seal was not installed completely correctly and it ends up being a seal that rolled a little in the channel allowing oil. An hour of labor and a seal and its all fixed- assumed they did not roll the seal again when they put the prop back on again - but at least that hour is not on you. . . .
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IOWs you don't know what a crank seal looks like :)
 
I chased a "oil on wind screen" gripe for two years until one day I saw the owner oiling the hinges of the cowling doors.
 
I had oil misting going on; we jacked around trying to blame the crank seal, the prop. Finally, cleaned the engine completely, put in some UV leak-finder juice (from the Aviation Chemicals Department at NAPA), and did a short hop. Turned out, a small leak at the case join on top, front. A little negative pressure, a little LocTite, alles in ordnung.
 
Found mine after pulling the spinner.....seal on the front prop dome seems to be leaking a little. A teaspoon of oil sitting in the spinner after a 2.5 hour flight and then sitting overnight. A small puddle under the nose of the plane where normal oil drainage doesn't normally go. Oh well......I wanted constant speed.

Frank
 
weirdjim said:
My GOD, man, you mean the thing didn't crash and burn taking the entire schoolyard full of children with it?

:D

.
Click to expand...

Well...

...it hasn't, yet. But it has only been three years or so...
 
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