The Cessna 120-140 Association Forum

Hi all,
My 140A with C-90-14F seems to have an oil leak coming from the bottom half of the alternator area. The prior owner had the alternator overhauled (it is the Ford style) and he is pretty sure the leak is not coming from the alternator shaft seal, but more likely the gasket between the alternator and the accessory housing.

In preparing myself and my IA for this work I have a couple of questions:

1. It sure looks tight to get the alternator nuts loose without removing one or both mags...is this correct? Or can this be done without removing the mag(s)?

2. The overhaul manual states to use a non hardening gasket sealer. Is Hylomar Blue an appropriate sealant for this job? If so, I already have some on hand.

3. I'm a believer in torquing fasteners to proper specs. I don't see how that can be done with the alternator nuts because about the only way I see to tighten the nuts is with an open end wrench. Do we just go with what feels about right on this?

I know my IA already knows how to do this job, but I wanted to get more ideas from the braintrust here too.

Thanks in advance for any advice.
Josh

If I remember correctly, removing the right mag makes the job much easier. I don’t know about Hylomar. I used Permatex non hardening sealant. I don’t think torquing the nuts is possible.

What he said, except I thought it was the left mag...

You need a crow's foot and maybe an extension if you want to put a torque wrench on those nuts. There are drawings in AC43.13 showing these tools and how to use them, but your A&P should know, and probably has the tools.

Do not be tempted to cut the gasket to avoid removing the tach housing. It will leak as you will cut right across the back of one of the oil pump shafts.

The alternator shaft seal is a little tricky. I recall there is also an o-ring needed to keep oil from migrating up the shaft to the other side of the seal.

If you are right handed, taking the left mag off will make the job easier.
For left handers, the right mag is the better one to remove.
Think about it.

Rick

Thanks so much for the information guys! Exactly the kind of feedback I was hoping for.
Josh