Drain Plug Question

[Rich76_911s]

Hey gentlemen,

Question here. I'm cleaning my case up getting ready to get the motor back together. As I was cleaning the case I realized that someone in the past used a helicoil for the drain plug.



1. Is this an appropriate fix for this? Note that the heli coil appears to have broken about 2 thread depths into the case. I'm a little disheartened to find it this late in the game, but want to fix it correctly as the case is still split.

2. Is it best to have this drilled out and have it tapped for a larger drain plug? As it was likely already opened up for the helicoil, is there enough meat on the bone here to do it again?
-Only concern is I wouldn't want an oil change guy to hammer down on this and crack the case.

I'd greatly appreciate some of your thoughts on how to best proceed here.

On a positive note, quarantine time has yielded a pretty clean case:




Thanks for any guidance,
Rich

[r lane]

Pretty sure they came that way, with a heli coil. You could very carefully attempt to remove that one and install a fresh one. If you could get a pick under it and begin to roll it out. Would avoid oversizing it if possible

[cmcfaul]

Have to choose your battles sometimes. Thant is not one I would choose. If it takes the torque to hold the plug and not leak...leave it alone. The fix might be worse then the percivied problem.

Chris
73 E
89 Carrera

[r lane]

My first thought was as Chris has stated. My second thought, it takes torque, the engine is built, and 2 oil changes later, it fails. Now what.

[Rich76_911s]

Uffdahh these are tough decisions. It was working and was not leaking for the 6 years I've owned the car.

THanks for the input gentlemen. Seriously appreciate the thoughts. I didn't realize that it originally was helicoiled in there.

Rich

[911pcars]

If it really bothers you, replace the threads now, but it's not a mystery engine. It's been yours for 6 years w/o leakage from that location. Use a fresh gasket and if it leaks after installation and running, a new thread insert can be easily installed. If it doesn't leak, buy us lunch.

If you want to go anal, apply Locktite 574 (or equiv.) on dry threads (a challenge at this location), then allow to set overnight before the refill. There's only atmospheric pressure and gravity behind the oil. I've used that on paper/cardboard/metal washers when I want to ensure a seal against potential leaks.

Sherwood

[Walt Fricke]

Unless this previously leaked, I'd not worry overly much. There is a nice cast aluminum finned sump plate guys with earlier cases like to use. It has what I see as a bit of a design flaw - the boss for where the plug goes is sort of shallow, and when drilled and tapped the threads are 360 degrees around only for what seems like not many turns. Deeper, the threads are only on a sort of semi-circle, with the other side of the threaded plug open to the oil/sump. On the one I inherited the threads had been damaged, probably by overtightening, and were failing. I inserted a Helicoil, which was made a bit tricky due to the fact that the coil was longer than the fully threaded area. But it works. The seal comes from the washer pressed between the case (for your engine) and the plug, not the threads.

You can test this easily - put the plug in, look up the proper torque, and torque it. See if that works. If so, should be fine. I don't know if this is factory, but it might be - this is a fastener/plug made for frequent R&R. Aluminum isn't good for that, so a steel insert makes sense. At least one of the engine to transmission studs or bolts has such an insert. No flies on Helicoils as far as strength goes. And you don't need many threads engaged to develop nearly full strength when it comes to torque.

But if you don't trust this, you could a) check farther to see if this indeed is stock (all the cases I have had were earlier and had plates), and if not, you could have this welded up and rethreaded - something you are in a position to do at this point. I don't think that is needed, but it is your engine and angst.

[targa72e]

I just looked at the drain on my 964 case (GT3) and it has a helicoil as well. I am going to assume this is factory (I have a 3.3 case I can check when I get a chance. End of helicoil was about 1-1/2 threads down the hole. I think your install is factory.

john

[911pcars]

Originally Posted by targa72e

I just looked at the drain on my 964 case (GT3) and it has a helicoil as well. I am going to assume this is factory (I have a 3.3 case I can check when I get a chance. End of helicoil was about 1-1/2 threads down the hole. I think your install is factory.

john

Congrats and apologies. I have stereotyped water-cooled owners as having their own private oil/filter maintenance crews. To a lesser extent, the same folks with the latest air-cooled versions. Sorry.

Many folks who do their own oil changes, as well as many working pros, tighten the drain plug like they're prepping for a once-in-a-life-time lunar lift-off event. Doesn't need to be spec tight, especially with a fresh washer and a smear of anti-seize.

Notice how the drain plug is somehow a lot tighter than than when you last screwed it on? Sometimes massively tighter. Heat and mileage somehow does that only to drain plugs, so does that lift-off crew. Must be a Teutonic thing.

There's another drain plug on the oil tank and I've reduced the odds of a failed attempt, by half, to remove one of the drain plugs. I use a Fumoto ball valve at the oil tank. Positively spring-loaded with an over-center release lever. It ensures positive drainage with no leaks or thread-destroying worries. Install it once like a drain plug (see above) and that's it for a looooong time.

Sherwood