Stripped oil drain plug Options

[smj]

Bringing the 914-4 back from mostly sitting for the past three years (under 1,000 miles in all that time), I forgot the oil drain plug was boogered up by a DAPO or oil change place...

Based on what came out, there were only a few shreds of thread somehow attached to the bottom of the drain plug hole, and a horribly mangled soft crush washer. Most of the "bore" is pretty smooth, with some original thread left at the top. Pic below.

My question is how to fix this. I see references to Heli-Coils, but somewhere I got the impression they need some thread left...? Whereas a Time-Sert or similar requires boring and fitting a thread insert.

How difficult is it to do this right with something like a Time-sert for a guy that reassembled some CV joints correctly on the *second* try? With the car up on jack stands in the back, so at an angle. And then what the heck do I use for a drain plug?

Thanks!

[JeffBowlsby]

How about using an oversized drain plug from FLAPS? They are self tapping.

[smj]

Really, self-tapping oil drain plugs? I honestly had no idea...

I did see a 2009 post ( http://www.914world.com/bbs2/index.php?showtopic=93648 ) that suggested using a pipe tap. Something like this: http://www.grainger.com/product/WIDIA-GTD-...-Pipe-Tap-2XTP3

[EdwardBlume]

How about using an oversized drain plug from FLAPS? They are self tapping.

(IMG:style_emoticons/default/agree.gif)

Looks like plenty of metal to tap.

[914Mels]

If you can find a larger size drain plug from another model car, just retap the case to the bigger size. Might be better than a self tapping option.

[yeahmag]

Time-serts are dead simple to use and a very nice product. Either re-tapping or using a Time-sert seems like a fine idea. Use some grease on the tap to help capture the filings.

[Sleepin]

I used a time-sert on my 1.8 and never had an issue after that. Simple (but slightly nerve wracking) to do and they work excellent!

[smj]

I notice that Time-Sert goes up to 24mm. So I reckon if normal tapping doesn't work, there's still a chance to try the other... (IMG:style_emoticons/default/unsure.gif)

ADDED: Called EASY in Emeryville before I ran out to the store. Already forgotten the gent's name if he gave it, but he recommended the pipe thread tap approach. I asked about using a slightly larger drain plug from some other model, but he said it would be difficult to find a tap to match the thread pitch used, at least compared to hitting a decent hardware store for a pipe thread tap and matching plug.

FWIW my calipers tell me the diameter of the stripped hole is 13.65-13.75mm, and I've got ~8.8mm of depth before I hit the remaining original threads. An old 944 drain plug I have on hand is over 19mm - seems like a lot of material to remove, ignoring the question of a tap with the right thread pitch...

[Series9]

Clean it thoroughly, take it to a welder, weld it closed, drill it out, tap it.

(IMG:style_emoticons/default/beerchug.gif)

[BobMC914]

As a cheap-ass, I would say tap it for pipe thread and buy a pipe plug to match. Both should be good and cheap at your local hardware or plumbing store, and effective as well.

[Mark Henry]

I did the pipe plug on my dads vanagon, it worked just fine and was dirt cheap because I had the 3/8 NPT tap.

Timesert would cost over 100 bucks just for a tap kit that you would only ever use once. In this case I'd find a shop with the right tap and let them do it.

Both methods use grease on the tap to catch the shavings, go slow and clean the tap often.

I guess welding is an option, but only if the engine is apart.

[porschetub]

Clean it thoroughly, take it to a welder, weld it closed, drill it out, tap it.

(IMG:style_emoticons/default/beerchug.gif)

Seriously you must be taking the p#ss (IMG:style_emoticons/default/WTF.gif) ,mark henry nailed it....good job.

[smj]

BTW thanks to everybody for your replies, I really appreciate this.

Clean it thoroughly, take it to a welder, weld it closed, drill it out, tap it.

No question that's The Right Way, but as others have said I imagine I'd have to pull the motor and split the case. That isn't really going to be my first choice, absent other issues...


ADDED: A 3/8" NPT tap was $9.99 and a 3/8" plug was $1.99.

The stripped bore is ~13.75mm at the mouth. Using calipers to measure the outermost diameter of the plug is 16.85mm. The pointy end of the tap is ~13mm, hits about 16.5mm halfway up, and 17.05 at the wide end of the threads. So it looks like I've got to drive that tap most of the way in to get a proper fit for the plug, but I'll take it in stages and check fit along the way. I expect the going will get a lot harder when I hit the original threads ~9mm in.

That is, once I get something to handle the 1/2" square butt of the socket. Didn't think about that when I bought it - the tap & die set I have is for things like #8 machine screws... (IMG:style_emoticons/default/unsure.gif)

[Mueller]

I swear I have not been drinking tonight!

Crazy idea time....

Know any machinist?


Drill out threads will large Silver & DEming drill bit, use new plate that screws into the bottom of the motor. Sorry, not to scale, only had a few minutes to draw this up..time to go bed! I'll read all the negative comments in the AM, hahaha

[mbseto]

I would think any regular bolt would work with a gasket washer. Just pick the right oversize, drill, and tap.

[smj]

It was a bit of a pain finding a big enough tap wrench/handle for this tap but I finally got one today. Then I put on my big boy pants, gritted my teeth, prayed I wouldn't screw anything up, and tapped the oil drain. Used some old wheel bearing grease liberally applied to the tap to help collect the shavings. Test fit the plug, bored a little more, worried I might cross thread, but it all seemed good.

Plugged it, put in two quarts of some old generic Sunoco motor oil, and removed the plug - and some turnings that had collected on top of it. After that drained, refilled with some fresh oil and after a brisk ~10 mile drive tonight it seems okay. I'll check for a puddle in the morning. (IMG:style_emoticons/default/wink.gif) I'll replace oil & filter again in around a 1,000 miles just because.

I did apply blue thread locker to the last (outermost) threads of the plug for a little extra piece of mind.