[1978alfa]

My duetto has a slow leak from the drain plug.
I pulled the plug yesterday, cleaned everything thoroughly, reassembled and tightened it.
The leak continues.
Do the copper washers need to be replaced periodically?
The surface of the washer appeared to be in good condition.

Centerline sells these:
Diff or Trans Drain Plug | Centerline International
Maybe time to use the newer design?
Thanks.

 

[Alfajay]

Do the copper washers need to be replaced periodically? The surface of the washer appeared to be in good condition.

Oh yes. The copper work hardens after being tightened/loosened a few times. You could anneal it, but replacement washers are available at your local NAPA store (bring the old one - they won't know what size fits an Alfa differential) as well as from the usual Alfa parts suppliers. I heard on the BB that Amazon even sells them. See: Amazon.com: uxcell 10Pcs 22mm x 28mm x 1.5mm Copper Flat Washer for Screw Bolt: Home Improvement This may be the size for the engine oil pan drain plug (are the diff and trans plugs a different size?).

Centerline sells these: Diff or Trans Drain Plug | Centerline International Maybe time to use the newer design?

Unless your old plug is stripped, I doubt there's anything wrong with it. That part from Centerline looks like the same design as the original. I'd concentrate on getting a softer washer.

 

[crackie]

Can find them at hardware stores, too. BTW "anneal" means heat it up with a propane torch (or gas stove for that matter) until "glow" hot (hard to tell with copper sometimes...dim light helps).

I just pass that along because I had to look it up the first time I saw the term.

 

[vintagemilano]

The two surfaces the copper washer is tightened against really need to be scratch free. The copper is unable to deform enough to fill in the void of scratches, so the oil slowly seeps through.
are you sure it’s the drain plug? Where is the drip hanging? Off the plug or bottom of the rounded portion of the rear half?

 

[1978alfa]

Drips are hanging right around the cast aluminum ring on the sump pan.
I'll pull the drain plug and put a fresh copper washer in this weekend when I have some time.
Rear end has a new main and lower pan seal, installed last year.
Thanks.

 

[zedsn]

If you can't find a copper washer you could put some pipe dope on the plug threads and tighten it up and let it sit a couple of days before refill and you should be good to go then.

 

[goats]

Sounds like pinion seal leak

 

[1978alfa]

.

 

[goats]

Roger that. Oil can run from the seal down to the annular ring around the drain— where it then drips off.. I would not expect a leaking drain plug to drip from that annulus.

 

[1978alfa]

I replaced the pinion seal and sump seal 18 months ago.
The leak started about 3 weeks ago.
Front of the diff case is dry.
Drips were hanging on the ring around the drain plug.
Car hasn't been driven in 10 or 12 days.
I pulled the pan earlier this evening to inspect it. Looks fine.
Fresh copper drain plug gasket, thorough cleaning and put it back together .
Hope that does the trick.

Plumber's tape is next!

 

[1978alfa]

The other x factor is the weather got cooler.
40 F at night several times in recent weeks. Metal contracts when the temperature drops.

 

[goats]

Ya know, I’ve heard that! For the diff and trans plugs, as well as the oil galley plugs in the head, I use Loctite thread sealing compound. Works good for me.

 

[alfaparticle]

I always anneal the copper washers in a propane flame and reuse them and I always use a torque wrench when I tighten them.

 

[1978alfa]

I thought about putting on my stove and warming it up prior to installing it.
Thanks.

 

[Gubi]

I thought about putting on my stove and warming it up prior to installing it

The copper washer? You'll need to heat it until it glows dull red. A torch does this quickly, dunno how well a stove will work.

Then let it air cool or quench it in water. I prefer the latter as it minimizes oxide buildup and keeps the copper cleaner, but either will work.

If it's a fresh washer from the hardware store you can just use it as-is.

 

[1978alfa]

I bought a fresh one yesterday from a car parts store.
Thanks

 

[1978alfa]

Update.
I pulled the sump pan off and inspected it. It looks perfect.
Dried it thoroughly and put it back on.
Fresh copper washer with plumber's tape on the drain plug.
Refilled the differential with Redline 75/90NS.
An hour later, I went back out and there were already a few drips hanging from the fins of the sump, towards the front.
The plug area is dry, so I know the plug with the new washer with plumbers tape is holding.
However, the car sat with the rear end jacked up for 2 days, so the sump was slightly over full since the fill plug is at the back.
Now there IS moisture coming down the front of the differential case, which was not there previously.
Maybe it was there, previously and I didn't notice it.
Anyway, it looks like the new seal I installed last year is already leaking.
A new seal and a fresh sump gasket, are on order.

 

[goats]

when you take the pinion nut and flange out, do look at the sealing surface of the flange, A groove can wear in it right where the seal rides, making it leak even with a new seal. The fix is a speedi-sleeve (i posted about this a few years ago). you might be able to find it using search
AND -- use thread sealing compound on the threads of the pinion nut! that might be where the leak is coming from --

 

[alfaparticle]

Putting tape on the threads will screw up the torque reading.

 

[goats]

thread sealing compound - it wont screw up the torque-- which I generally dont use when R/R pinion nut -- I mark it, then go back to where it was,,,,,,