The International Cessna^® 170 Association

My C 170B , O 300D, with a Ford Alternator , ( DFO_____? ) has develpoed a static oil leak.
I am on the road until Wed night, so I have no access to my manuals. Does anyone know the part number
of the oil seal which I believe goes on the Alternator, which I believe, is the likely cause of the static leak.
I would like to get the seal ordered , so I can get the seal changed when I get home Wed night.

Thanks John

Don't forget you will need a PN 652072 gen/tach gasket:

Yes, and remove the tach assembly tro use the complete gasket !

And DONT FORGET to use a new oil seal for your tach drive shaft: PN 642714

I'm thinkin' that if you call Aero Tech of Louisville they can simply tell you which seal, and sell you the part as well. (incl. the ones we've just mentioned.) (502) 263-7090
Talk to John.

Thanks George,
Tach seal pn 642714, gasket pn 652072. That is great thanks.
I can call Aero Tech, on Monday, I am hoping to get the alternator oil seal number part number,
so that I can order it locally in the Toronto area, to avoid shipping costs and delays,
I am guessing the shipping would cost more than the parts ?????

Any one know the alternator, oil seal part number ???

As long as it is being removed, what about the coupling? Is there excessive play? We ran into the same situation and appears the coupling has a little to much play, so gasket and coupling are in order for us. Not sure if you have the same situation. Just a suggestion. I had a drawing of the 2 different couplings to post, but can't find it now for the life of me!

Thanks Kurt,
Good point, the coupling, do you know the part number ??
I have just over 400hrs on the alternator, so I was thinking of just changing the brushes,
once I had the Alternator off.


John

jatkins wrote:Thanks Kurt,
Good point, the coupling, do you know the part number ?? ....

There's a TCM service bulletin on this. Go to http://www.cessna170.org/forums/viewtop ... 02&p=60881

Thanks John,

Now I have ;

gasket pn 652072
tach drive oil seal pn642714
alternator oil seal ES4142
alternator brushes E4118
drive coupling pn632050

All as 500 hr service for the alternator.
I am going to do it about 60hrs early, as the Mag 500hr inspection
is coming up as well in 60 hrs.
John

Don't forget the o-ring ES4140. My spacer also had a groove worn in it and had to be replace (ES4141).

For my fellow Alaskan's, use Seaplanes North (formerly Floats Alaska) at Lake Hood for your cessna parts and avoid the $35 shipping costs using online vendors. Seaplanes North does charge a buck or two more for each part, but no shipping charges and they have the parts in a couple of days.

Here are the parts I needed...

Reviving an old post. Does anyone know which way the spacer (ES4141) and the O-ring (ES4140) goes in? Does the O-ring fit into the groove in the spacer? There is a small recess that looks like the O-ring goes into, but not 100% sure this recess is for the O-ring or the orientation of the spacer.

As the pulley gets torqued, the o-ring should seal on the shaft at the bearing. The spacer is probably to hold the o-ring in place with the groove.

John

The seal faces the engine so as to retain oil inside the engine. (Don't make the common error of installing it as you might other accessories.)

Great. Thanks for the information. It looks like the seal and O-ring went in the correct way, but the spacer went in backwards. Appears the O-ring should fit it the machined recess on the spacer.

The rotor shaft on my alternator had over 0.030” endplay even after the flanged castle nut was tightened. (Alternator Charging System Service/Parts Manual (D5107-1-13) specifies torque of 60-240 in.lbs., SB95-3B calls for 175-200 in. lbs.). Because the shaft is stepped, it’s impossible to reduce the shaft end play further if the nut has bottomed out on the shaft. (See photo). If there is any end play, the o-ring (ES4140) wil not be in firm contact with the front bearing (X4612) and will not seal. The spacer (ES4209) that the o-ring fits in has a very loose fit on the shaft so if the o-ring is not tight against the front bearing oil will migrate along the shaft into the alternator. My solution was to add a 0.060” shim washer as seen in the second photo to insure that the castle nut was not bottoming out on the shaft.