I think I found the oil leak on the bottom of my engine. When they rebuilt it, they installed screw-in oil galley plugs. This one, on the front of the engine, appears to be the leak -- it was a little loose and there was oil all over the back of the motor mount bracket.
Click to view attachment

The plug is 22mm with 1.5mm thread, straight thread (no taper), and is fairly short. It looks like they might have used a very small amount of gasket shellac to seal it originally. They did stake the plug, and it didn't rotate, but it unscrewed very easily and turned-in just a little past the stake when I tried putting it back in.

What should I use to seal this plug? I'm guessing pipe dope isn't the right stuff, since the plug isn't tapered. More gasket shellac? Red loctite? Something else?

Thanks!

If remove and reinstall is an option, perhaps Loctite 574. A Porsche trained mechanic uses it for not just case sealant but some plugs like the one in the end of the intermediate shaft. BTW - This is a good read on various case sealants.

If you're looking for something to apply to the exterior, Wayne Dempsey's engine building book recommends JB Weld in places where Porsche used epoxy (i.e., freeze plugs on 911 engines). Not sure about 914.

I have already removed the plug and cleaned up it and the hole. I am ready to reinstall the plug, but not sure what to seal it with.

I don't like the idea of epoxy, since I may want to get it out at some point.

That one is a factory plug and as you’ve noted, it’s straight thread which doesn’t help in the least.

Needs thread sealant. Avoid PTFE tape and use a real thread sealant. In past I’ve used PTFE paste and Permatex (separate builds) and had good results.


In this day and age I’d bet money Loctite has a better specialty product but will cost lots of money for a few drops and then the bottle will never get used again till it’s lost or dries out.

As always, results will depend on getting the threads immaculately clean, dry and free from oil before the reinstall. I’ve done that in past with real chlorinated brake cleaner and Q-tips.

I have seen people seal them (externally) with JB weld on the outside. As long as the allen drive isn’t filled, the JB weld would crack off if the plug ever needed to be removed.

Not a fan of that approach on a 914 but I once sealed a hole in a Miata oil pan (emergency situation) with JB weld and it worked great. Again was immaculately clean before application. Literally held for years until I scrapped the car. I’d call it DAPO work though! Just made no financial sense to weld or replace the pan on a car that headed for scrap a couple years later.

The one thing I’ve never liked about this plug is that it is a steel plug in an aluminum case.

The differing thermal expansion between the metals poses a real problem.

I have two engines that will be rebuilt when I get my garage built and my shop put back together.

I’m planning on making this plug out of aluminum to see if I can solve its propensity to weep. I’ve never had occasion to remove that plug once an engine was assembled and I can’t come up with a logical reason the plug was made of steel in the first place besides cost and off the shelf availability.

Will be years before I get a chance to do this but I’m looking forward to trying it to solve this problem area on the T4 engine.

I used aluminum pipe plugs with ARP thread sealant, no leaks.

@Geezer914 What size aluminum plugs did you use, and where did you get them?

I've been googling, and found only one place that listed M22x1.5 aluminum plugs, but they were out of stock. Apparently used by some Fiats.

I'm thinking about trying to make an aluminum plug, but not sure how to drive it. Don't have the tools to cut an internal hex hole.

Mill cut a slot or external hex with crush washer was what I’m considering. Both easy to turn on lathe.

The other thing I’ve done in past is to heat billet near plastic deformation (steel or aluminum - works with either) - hammer drive or press in hex (old allen wrench as form tool). Then turn the billet to what you need to duplicate original plug size and threadform.

I thought about the slot, it's pretty simple. External hex won't work because the stock engine mount bracket sits right on top of the threaded boss -- there's very little room between the boss and the bracket.

I'm going to try a different approach first. I ordered a couple of aluminum 3/4" NPT pipe plugs. They already have an internal hex, even if it is SAE and not metric. The plan is to turn down the outside of a plug and rethread it to M22x1.5. The plug shouldn't require a lot of torque, so I'll cut some of the hex end off to get it to the right thickness. Then, I'll use some Loctite 574 for sealant (amazon has small tubes of it).

I installed aluminum 3/4 plugs into the hole after the oil plug was removed and drilled and threaded for a pipe plug.

That's the same plug I fought last year. See my rebuild thread (starting at #6618).
http://www.914world.com/bbs2/index.php?sho...193&st=6600

One lesson: the threads on the plug and case have to be clean. I mean really, REALY, ABSOLUTELY clean.

@bkrantz Thank you for the link, Bob. Is your brass plug still holding?

I followed a link in your thread and ordered an aluminum plug from Racetronix. I'll try cutting the cap off and see if there's enough hex hole left to install the plug (new Plan A) -- based on the drawing on their site, it looks like it will work. Otherwise, I'll try the (now) Plan B and see if I can turn down and rethread an aluminum pipe plug. Plan C will be a brass plug, if needed.

The aluminum plugs arrived today -- I ordered extras just in case, and next-day shipping worked out to 18 cents more than regular shipping (who knows what's going on with Fedex in Canada).

Here's a pic compared to the stock plug:
Click to view attachment

The plug is the right size and length. The only odd thing is the hex hole in the center is 3/8", not metric (9mm is loose and 10mm won't fit). I cut the head off with a hacksaw, and the result is about the same thickness as the original steel plug.
Click to view attachment
If I were to make more of these, I'd tool up and trim the plug down with the lathe, but that was too much work for just a one-off (I'd have to make a fixture to hold the plug without damaging the threads.).

I got the plug installed, and it looks like it will work just fine. I'll write up more detail about everything in the un-dapo thread (post #135 here: http://www.914world.com/bbs2/index.php?sho...d=3126262&# ).

Holding so far. I don't want to jinx myself, but yes.

@bkrantz
thats good go hear! my battle last year was with pushrod tube seal on #1 and that RMS, which now has been dry for about a year now, good luck @BillC you will succeed i am sure!,