crankshaft oil seal leak

[3993v]

After 650 hours on our 170A's C-145-2 engine which was overhauled 4 years ago the crankshaft oil seal behind the prop flange started leaking. On the annual I changed the seal using continentals recomended primer, sealant and GN paste on the lip. Now 25 hours later it has started leaking again. When I installed the new seal I made sure that the split line of the seal was not in line with the split line of the case halves and that the lip spring was correctly installed on the lip making sure it did not pop off on installation, which is how I found the spring when I removed the old seal. The leak is a seap from the lip area that comes out of the front of the cowl and speckles the windshield. Has anyone else had this problem and can recomend a good course of action? thanks nick

[ron74887]

Nick, check your crankcase vent line. Mine was plugged up by a *&&%$$#* dirt daubber and could have blown the seal. When I landed I was looking thru a small clear spot on the side of the windshield. It started out with small dropplets and the longer I flew the worse it got!!!! I never thought they would build a nest with the oil influence on the lines. Ron

[3993v]

Thanks Ron I will check that tomorrow, Although I did notice that oil was driping out of the line after the flight, the line could still be partialy or nearly completly blocked. nick

[ron74887]

Nick, mine dripped also. and I never thought of checking that. I did fly for about 3 hrs since I was vfr on top and not smart, which many here will probably acknowledge. But since I was told It was nice where I wanted to land was not so. By the time I got home it wss covered and since have been told if it blew I had a few minutes before it lost all the oil and then I was really up the creek! And we all know the creek I'm talking about!! Ron

[3993v]

Thanks again Ron, I will definatly be checking that tomorrow. nick

[blueldr]

You're sure it's the nose seal aren't you? I had those symptoms and it turned out to be the "freeze plug" type plug in the crankshaft front lournal had come out and the engine was breathing out throught the front of the flange and prop.

[hilltop170]

And if it's one of the new drilled Continental crankshafts for an IO-360 Continental with a constant speed prop, if that little 3/8" plug inside the front of the crank falls out, you have however long it takes to pump 8 quarts thru a 3/8" hole at 45 psi.

It has happened to me twice in 100 hours since installing a brand new crankshaft. Continental says there is no problem. I asked the tech rep next time it happens maybe he would like to go for a ride and tell me there's no problem when the windshield covers up with oil and there's one thread left holding the plug in after 10 minutes from when it started leaking.

[tweiss]

Nick,
My last 170 had an 0300-D with the same leak, and it tormented us for about 4 new nose seals before we got it to stop. The first time it leaked we felt good about replacing it with a fresh new seal. But by the third time, well you can imagine the frustration.
The engine would run nice and dry for aprox. 25 to 75 hrs. after a new seal was installed, then the light speckles would begin to show on the windshield. The amount of leak would never increase beyond light speckles. I would fly it that way for another 25 to 75 hrs. until the next annual when we would replace it again.
I would suggest to you to determine if your leak is between the crank and seal (inside diameter), vs. the crank case and seal (outside diameter). Mine was leaking between the crank and seal.
After all the trouble shooting, including things people have mentioned above, the final fix came from some service bulletin
(I remember reading it, but I don't remember where it was from).
We used emery cloth and scratched in a screw like pattern on the crank where it passes through the nose seal in a fashion that if any oil tried to seep forward on the crank past the seal, the grooves we scored into the crank would drive it back into the case like a threaded shaft.
I will try to come up with that SB, I know my written description lacks much for a guy to just start sanding on a crank shaft with emery cloth.
I can tell you however that I flew the plane for another two years, leak free before I sold it.

Good Luck

Tom Weiss

[GAHorn]

Tom,
That is exactly what I was going to recommend, but you described it just fine. Inspect the crank surface for scratches or damage/rust, etc.... then using emory, polish it evenly and with a final emory cloth, polish a "swirl" pattern such that the regular rotation of the prop encourages the oil to be moved back into the engine. (This is frequently done on main bearing oil seals in auto engines, as well.)

EDIT:

ContinentalSB-M76-4 2.pdf

(89.96 KiB) Downloaded 142 times

[3993v]

Thanks for the help everyone, so far I have verified that the vent tube is clear, and as far as where the oil is seaping from, the first oil seal was from the lip area, however this time it might be from the seal to crank case area one small spot was wet between the seal edge and the case and there was oil directly below that spot running down the front of the case to the oil pan. I will have the new seal tomorrow so this weakend I will change it out. I think maybe the sealant in that spot some how got contaminated when I installed it, I hope to know more when I remove the bad seal. Some one correct me if I am wrong but as long as the vent is clear the crank case should not be getting overpressurized right? I also did check that the freeze plug was dry and it was. Does any one know the number of the SB for polishing the crank? Thanks for all the input and I hope to know something in a few days. nick

[53B]

Hi,

That would be TCM Service Bulletin M76-4. Sorry I don't have a copy to post.

[n2582d]

[3993v]

Thank you for the SB I will let you all know what I find this weakend. nick

[3993v]

Well I am finally ready to update. First prior to removal of the offensive seal, a close inspection revealed a small wet spot between the crankcase and the seal edge at about the 9 o'clock position as viewed from the capt. seat. On removal I found at that location a small tear in the seal face(where the sealant would go between the seal and the crankcase) all of the oil was running down that side of the oil pan as well. When I installed the seal at one point while trying to push it in the case it squirted around and got calked in the crankcase bore. I am thinking that this is when the seal got torn. So when we installed the second new seal we first cleaned the case very well, then we polished the crank shaft and finally made a two piece wood tool to press the seal in flat and streight, which this time it went in very nicely. We have about 4 hours on it now with no leaks. Now we are just going to fly it and hope for the best, thank you to all for the advice and help, it is always appriciated. nick