Leaking Generator Seal

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Leaking Generator Seal

Postby reecewallace » Sat Jun 19, 2021 5:31 am

Hi all,

I fixed one leak now onto the next—

My generator is leaking from an internal seal, not the one which attaches to the case. See photos below.

This genny was completely overhauled about 80 hours ago, but now leaking. It's a Delco 20amp generator part #1101890. Any idea on part # or where I can find it? I couldn't find it in the 170b catalog.
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Re: Leaking Generator Seal

Postby GAHorn » Sat Jun 19, 2021 6:07 am

See post : viewtopic.php?f=24&t=8466&p=75311&hilit=generator+oil+leak#p75311

There’s a gasket, an oil seal, and an O-ring and a tach drive oil seal (642714 superceded to 640087 (or 641533 if you have the new style accy case with the “bent” oil-cap-tube) involved. Keep in mind that the oil seal is designed to keep oil IN THE ENGINE…so take care which way it faces.. These are all in the TCM X30014 Parts Catalog.

To order the parts: https://www.aircraftspruce.com/catalog/ ... tparts.php
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Re: Leaking Generator Seal

Postby reecewallace » Sat Jun 19, 2021 2:56 pm

GAHorn wrote:See post : viewtopic.php?f=24&t=8466&p=75311&hilit=generator+oil+leak#p75311

There’s a gasket, an oil seal, and an O-ring and a tach drive oil seal (642714 superceded to 640087 (or 641533 if you have the new style accy case with the “bent” oil-cap-tube) involved. Keep in mind that the oil seal is designed to keep oil IN THE ENGINE…so take care which way it faces.. These are all in the TCM X30014 Parts Catalog.

To order the parts: https://www.aircraftspruce.com/catalog/ ... tparts.php


Thanks for this.

So I need to replace the gasket, oil seal, O-ring and tach drive oil seal? Are these 4 different p/n's?

Or

Just p/n AN123864: the seal, o-ring, oil resistant (superceded p/n 640087)?
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Re: Leaking Generator Seal

Postby Bruce Fenstermacher » Sat Jun 19, 2021 11:01 pm

The job is not an easy job. Requires draining the oil, removing both the tach drive and generator, cleaning the gasket from the accessory case, the tach drive and the generator. It would be foolish not to replace the seal in the tack drive while you are there. As for the seal or the o-ring in the generator, again, if you could tell which was leaking, which you can't, foolish to replace only one. As for a new gasket which goes behind both the tack drive and the generator, it would be a real trick to remove the tack drive and the generator and still have a reusable gasket. So yes you need a gasket, two different seals and an 0-ring.

You might want to do this at at oil change though you could recycle your oil back into the engine after draining it, if it has service life left and you took care not to contaminate it.
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Re: Leaking Generator Seal

Postby reecewallace » Sat Jun 19, 2021 11:38 pm

Bruce Fenstermacher wrote:The job is not an easy job. Requires draining the oil, removing both the tach drive and generator, cleaning the gasket from the accessory case, the tach drive and the generator. It would be foolish not to replace the seal in the tack drive while you are there. As for the seal or the o-ring in the generator, again, if you could tell which was leaking, which you can't, foolish to replace only one. As for a new gasket which goes behind both the tack drive and the generator, it would be a real trick to remove the tack drive and the generator and still have a reusable gasket. So yes you need a gasket, two different seals and an 0-ring.

You might want to do this at at oil change though you could recycle your oil back into the engine after draining it, if it has service life left and you took care not to contaminate it.


Thanks for this. I’ll plan to do it at the next oil change, because surprisingly this tiny leak makes a HUGE mess which runs down the belly of my plane. The photos are right after I cleaned it.

I agree, smart to replace all the gaskets/seals to avoid doing it again.

Can you tell me which p/n’s I’ll need to order to cover all my bases?
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Re: Leaking Generator Seal

Postby GAHorn » Sun Jun 20, 2021 1:31 am

reecewallace wrote:
Bruce Fenstermacher wrote:The job is not an easy job. Requires draining the oil, removing both the tach drive and generator, cleaning the gasket from the accessory case, the tach drive and the generator. It would be foolish not to replace the seal in the tack drive while you are there. As for the seal or the o-ring in the generator, again, if you could tell which was leaking, which you can't, foolish to replace only one. As for a new gasket which goes behind both the tack drive and the generator, it would be a real trick to remove the tack drive and the generator and still have a reusable gasket. So yes you need a gasket, two different seals and an 0-ring.

You might want to do this at at oil change though you could recycle your oil back into the engine after draining it, if it has service life left and you took care not to contaminate it.


Thanks for this. I’ll plan to do it at the next oil change, because surprisingly this tiny leak makes a HUGE mess which runs down the belly of my plane. The photos are right after I cleaned it.

I agree, smart to replace all the gaskets/seals to avoid doing it again.

Can you tell me which p/n’s I’ll need to order to cover all my bases?


Reece… you are being redundant. I provided all those PNs in those previous posts.
'53 B-model N146YS SN:25713
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Re: Leaking Generator Seal

Postby reecewallace » Sun Jun 20, 2021 4:23 pm

GAHorn wrote:
reecewallace wrote:
Bruce Fenstermacher wrote:The job is not an easy job. Requires draining the oil, removing both the tach drive and generator, cleaning the gasket from the accessory case, the tach drive and the generator. It would be foolish not to replace the seal in the tack drive while you are there. As for the seal or the o-ring in the generator, again, if you could tell which was leaking, which you can't, foolish to replace only one. As for a new gasket which goes behind both the tack drive and the generator, it would be a real trick to remove the tack drive and the generator and still have a reusable gasket. So yes you need a gasket, two different seals and an 0-ring.

You might want to do this at at oil change though you could recycle your oil back into the engine after draining it, if it has service life left and you took care not to contaminate it.


Thanks for this. I’ll plan to do it at the next oil change, because surprisingly this tiny leak makes a HUGE mess which runs down the belly of my plane. The photos are right after I cleaned it.

I agree, smart to replace all the gaskets/seals to avoid doing it again.

Can you tell me which p/n’s I’ll need to order to cover all my bases?


Reece… you are being redundant. I provided all those PNs in those previous posts.


Pardon my redundancy, but I only see p/n 640087 in your response above for the tach oil seal, and p/n AS3570-111 O-ring from your previous post (item 13 fig 16).

These two parts:
https://www.aircraftspruce.ca/catalog/e ... key=118104
https://www.aircraftspruce.ca/catalog/e ... -06188.php

Am I mistaken that I should be looking for 4 p/n's?
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Re: Leaking Generator Seal

Postby lowNslow » Sun Jun 20, 2021 7:01 pm

Reece, from the photos above it looks like you have the fiber gasket on you oil filter adaptor, you may want to change it at your next oil change per the service bulletin.

download/file.php?id=16076
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Re: Leaking Generator Seal

Postby reecewallace » Sun Jun 20, 2021 7:11 pm

lowNslow wrote:Reece, from the photos above it looks like you have the fiber gasket on you oil filter adaptor, you may want to change it at your next oil change per the service bulletin.

download/file.php?id=16076


Thanks for this. That was the plan. When I purchased the spin on adapter, the STC instructions were old and instructed to use fiber gasket. Since then, I spoke with Tempest and they advised me to switch to crush washer. No leaks on it yet fortunately!
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Re: Leaking Generator Seal

Postby GAHorn » Mon Jun 21, 2021 5:02 am

Reece, did you look at the Aircraft Spruce link? There’s an Oil seal and a generator gasket depicted there. The first link provided the O-ring.

Here’s where you can order the tach drive oil seal: https://www.aircraftspruce.com/catalog/ ... ey=1448869
'53 B-model N146YS SN:25713
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Re: Leaking Generator Seal

Postby reecewallace » Mon Jun 21, 2021 6:34 am

GAHorn wrote:Reece, did you look at the Aircraft Spruce link? There’s an Oil seal and a generator gasket depicted there. The first link provided the O-ring.

Here’s where you can order the tach drive oil seal: https://www.aircraftspruce.com/catalog/ ... ey=1448869


Okay, I think I've got it figured out now.

4 parts total. Please confirm with me I'm correct:

GENERATOR GASKET p/n 652238
OIL SEAL p/n 352068
SEAL-O RING AS3570-111 p/n 07-06188
TACH OIL SEAL p/n 642714

I also see in the diagram it has 'starter gasket' (part #9) next to the generator gasket. I find this odd. Do I need to order the starter gasket too? My start is above my generator...
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Re: Leaking Generator Seal

Postby GAHorn » Mon Jun 21, 2021 12:16 pm

I don’t know why Spruce put the starter gasket in that particular chart (unless they figure removing the starter may give additonal/easier access to R&R the generator.. No you probably do not need it.
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Re: Leaking Generator Seal

Postby reecewallace » Mon Jun 21, 2021 6:58 pm

GAHorn wrote:I don’t know why Spruce put the starter gasket in that particular chart (unless they figure removing the starter may give additonal/easier access to R&R the generator.. No you probably do not need it.


Figured. I won't order the starter gasket.

Another question—

What's the part # for the oil drain crush washer? Not the quick sump drain, but the drain plug beside the spin on filter adapter. You can see the small crush washer in the picture above next to the adapter.

My oil system looks different than the one pictured in the TCM
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Re: Leaking Generator Seal

Postby GAHorn » Mon Jun 21, 2021 7:14 pm

reecewallace wrote:
GAHorn wrote:I don’t know why Spruce put the starter gasket in that particular chart (unless they figure removing the starter may give additonal/easier access to R&R the generator.. No you probably do not need it.


Figured. I won't order the starter gasket.

Another question—

What's the part # for the oil drain crush washer? Not the quick sump drain, but the drain plug beside the spin on filter adapter. You can see the small crush washer in the picture above next to the adapter.

My oil system looks different than the one pictured in the TCM


Reece… I suggest you download copies of the Illustrated Parts Catalogs for your aircraft and your engine. That way you can be more familiar with the terminology as well as find part numbers.
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Re: Leaking Generator Seal

Postby reecewallace » Mon Jun 21, 2021 9:35 pm

GAHorn wrote:
reecewallace wrote:
GAHorn wrote:I don’t know why Spruce put the starter gasket in that particular chart (unless they figure removing the starter may give additonal/easier access to R&R the generator.. No you probably do not need it.


Figured. I won't order the starter gasket.

Another question—

What's the part # for the oil drain crush washer? Not the quick sump drain, but the drain plug beside the spin on filter adapter. You can see the small crush washer in the picture above next to the adapter.

My oil system looks different than the one pictured in the TCM


Reece… I suggest you download copies of the Illustrated Parts Catalogs for your aircraft and your engine. That way you can be more familiar with the terminology as well as find part numbers.


I have the one for the aircraft, but didn't know there was a separate one for the engine.

Where can I find it? I don't see it under the 'Technical Documents'
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