Brass drain plug into aluminum casting.

Usually a copper crush washer is interposed between the mating surfaces of the plug and the boss. I think the plug you show is actually cadmium plated steel giving it the yellow color. If a drain plug, just use the proper crush washer and orient it flat side to plug sealing flange and rounded convex side to the drain pan sealing surface, Torque to specification in WSM. No anti seize needed.

 

If it was a pipe thread, then yes, you’d want to use anti-seize. Your drain plug is not a pipe thread, so like Snapshift said, use the correct crush washer and that’s all you need.

My Harley has a similiar drain plug and it uses a small rubber o-ring that fits into the tapered area of the drain plug.

Just use what it came with originally and you’ll be good.

 

They are solid brass. Zero need to orient proper crush washer in any particular direction. They are torqued to yield of the copper making its slight surface shape differences irrelevant.

 

In cases like this its almost never a bad idea to emulate what the factory does. Put nothing on it but a new copper washer.

 

The bigger problem is overtightening and stripping the aluminum casting. Which putting antiseize on the threads will make that more likely.

That "torque to yeild" of the crush washer is an experience based thing. Snug rather than tight seems to be the best description.

Brass and aluminum do have some galvanic potential, but not as much as between eg. steel and aluminum. An oil plug will have oil creep into the threads (and then sealed by the copper crush washer), so that oil will be enough to prevent the minor galvanic action. Best to install with clean, dry threads.

 

Same issue with my oil-pump plug (the one that holds the pressure regulation spring). Car was rebuilt three years ago, but the plus is already locked on the casing. The plugs that are often removed are not so troublesome, but the ones that are serviced on seldom occasions can be a pain to remove.

Just curious to see if some are doing it differently than the factory. After-all the factory probably did not work the workshop manual for the mechanics that would service the car 50 years after it left the factory...

 

That is misinterpreted all the time. The plugs take far more effort to remove than what was used to install them. The big plugs like TR transmission drain plugs I just use a standard socket but use a 1/2 air gun to break it loose. Just the way it is. They need to be tightened just until you can feel the copper slightly crush which I do on those same plugs with a regular 1/2 inch breaker but 1 minute later it will take the air gun to break it loose. Every week I remove plugs I installed and that is just SOP.

 

Wow, hard to imagine the aluminum threads don't shear right off with all that force. Must be some galvanic action at work.

Maybe some Nylog thread sealant, used by the AC technicians would be a good idea.

 

That has nothing to do with it. When a plug is reinstalled it has a liberal amount of lubricant in the form of the oil you were just draining out.
Its a function of the friction created by the copper sealing washer on that 38 or 42mm plug.

I take them out every week, same plugs I installed a year or so before. Go in at 50 Lbs or so and come out with an airgun. Been doing it since Boxers were in production.

 

I guess that explains why a copper sealing washer seals so well when compressed the right amount. No wonder that is what is used on high pressure fittings in particular.

 

Is there any thing special required when installing brass drain plugs into aluminum castings? Should I use anti-seize or maybe lightly coat the threads with gear lube?

 

Did you read any of this?

 

Seems a good idea: the Nylog, would allow to seal the plug without any brute force, which would give us some peace of mind while tightening lightly as per Rifledriver guidelines... this being said, we should use the original (red?) Nylog meant for r12 (i.e petroleum lubricant).

 

I think Nylog Blue is more common, and is also petroleum based. But yes it appears Nylock red labeled as miscible with the old style mineral oil ac lubricants.

I did use some for when I converted my R134 system, and have also used it on the coolant drain plug in the brass radiator tank, which looks prone to stripping and made me concerned with overtightening.

The problem with all these copper washered plugs is a stripped plug can be a minor disaster, and only experienced hands can torque to yeild reliably. I have worked on cars as a hobby for along time, and still worry about stripping, the instinct always seems to favour overtightening.

 

If you are incapable of feeling a slight crush in the copper washer, instead of doing it incorrectly and knowing you are doing it incorrectly my advice would be to have it done for you.

 

The engine and transmission drain plugs on my 85 308 and 95 355 are plated steel and the torque spec for the oil lug is 37 ft-lb (50 N/m).

 

Yes, that is true, I do not feel that crush, and always wonder why not when everyone else seems to feel it is so obvious. I suspect I am not the only one who worries about stripping threads, which is not a trivial outcome.

 

Neither is falling out on the ground and losing oil. If you are incapable of tightening it properly that is a very real and worse possibility.

 

My method is to use a 1/2" breaker bar to remove these plugs, but switch to a 3/8" ratchet or 3/8" torque wrench to install them.

I've never had a problem with stripped threads or plugs coming loose that way, it seems to give better feel for the gasket compression with the smaller tools.