Bad nut
 

I am having a leak from this stud from the bottom of my 2.7 engine. Correct me if I am wrong, but I think it's a bad nut because I have put a number of washers behind the nut and tried to tighten down and it wouldn't take any tightening.
So anyways its leaking from this area that I have never been able to tighten and so I have lived with the leak, until now. Can I find this nut at a large hardware store or do I need to order it?




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Probably, the magnesium is pulled. Use 8mm, double nut with out nyloc and see if you can thread until you seat.
The option is opening the case and time sert the studs including the long one by the intermediate shaft.
The nut is a standard 8mm nyloc, any hardware store should have it.
Bruce

The stud is obviously pulling out of the case. A good fix is to get the stud out and run a 10X1.25 tap in the hole about an inch deep and use a very short 10mm bolt and sealing washer. If the engine is ever apart, a timesert can be used to do a proper fix. I do this a lot on the usual leaker below #1 cylinder.

What do you mean the magnesium is pulled? Will look for a 8mm and report back.

When you say the stud is pulling out of the case, are you saying the stud sits a little too far out from the case? How would I get the stud out?

Double nut it.

What they are saying (reminding you of) is that you have a magnesium case, which is softer than an aluminum one. Sometimes the magnesium begins to fail/fatigue around the studs because of over stress (usually associated with the tightening of the studs) or heat cycling over time. Double nutting it to tighten it more or trying to tighten it more by trying to turn the nut on it will make the problem worse. John Walker's advice is right on (as usual). Removing the stud and tapping it with a slightly larger stud and cutting new threads into fresh case material is the best without splitting the case. When/if you ever have to split the case, you can timesert it. You may be able to get the stud out by double nutting and backing it out or using a stud removal tool. If it is in the process of pulling out (which is why you keep tightening & to no avail), it most likely won't be difficult to get out.

Steel is hard. Magnesium is soft. Over time, with as many heat cycles as have occurred with each engine run, shut down and restart, the thermal expansion differential as well as the working of the softer metal, has caused this steel stud to loosen in the magnesium case. The fix is to install a time-cert to give a stronger point from which the nut on the stud can be tightened. Comments above indicate that this common repair is in your future.

In my past I've only worked on older domestic vehicles and this is a european vehicle that has hardware issues that I have never had to deal with. The nyloc nut was something new to me and I discovered that the nyloc can only be used once and this might explain why I cannot get the nut to tighten to the appropriate torque. Since I am doing a show this weekend, I am going to use a new nyloc nut until a later time to remove the stud.
This engine was rebuilt a few years ago and perhaps has a few thousand miles since, is this issue with the stud so early, common or more of an anomaly?
When I reinsert the stud, how much should I torque it before I put on the nyloc nut?

A quick fix can be, remove the stud using double nuts, loctite the threads, re-install and use a fresh Nylock.

Thanks for that tip. Do you think, since the engine was rebuilt a few years and a few thousand miles ago, that I should be having this problem?
I know that the miles that were put on before me and after the rebuild were not hard miles.

That stud is not something messed with during a rebuild. It's a fix needed, when needed, if you get my drift.

The loctite solution is a band aid and will likely come loose again.

One more question, what is the torque value for this nyloc nut?
Thanks

There are no threads left to reinstall a stud. They have pulled out of the other side of the case. A new nut will not work. With my fix, you stop the leak. The 10mm tap will thread the first inch of the left case half using the original hole, no drilling needed. You're basically making a plug.

Some of those studs go all the way through the right half and if you have a long stud you could washer and nut each side.
Bruce

On this engine the studs don't go through to the other side as you can see in this photo.



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That the way to fix that leak.

Yes, they absolutely do - that's how the perimeter of the engine case is held together. Look again at your own photo - the stud is anchored on the case half in the right side of your photo, and torqued down to the other case half with the nut on the left side. To be more specific: The stud is anchored (threaded) in the case half on the right, passes through (unthreaded) the case half on the left, and is then nutted down on the left.

The question about the torque is irrelevant. It won't torque. Using a new nut is irrelevant - until you 'patch' the situation with John Walker's fix, or properly fix it with a threaded insert, it isn't going to take a torque.

Look closely at the stud you've been trying to torque the nut down on. Compare it to the other similar studs in the vicinity. Notice how that one is sticking out more than the others around it? That's because every time you try to torque a nut down, it is pulling the stud further out of the case.

Now that you have that much stud sticking out, just go ahead and thread two nuts onto the stud (just far enough so that both nuts are on the stud - don't tighten them down to the case). Tighten them up against each other with a pair of wrenches. Then, using a wrench counter-clockwise on the nut that is closer to the case, back the nuts, and stud, out of the case. Then apply John Walker's 'patch' method until such time as your engine is torn down, if ever.

Thanks for the response. In reference to the statement "Some of those studs go all the way through the right half and if you have a long stud you could washer and nut each side. I submitted the photo to show that the stud doesn't go all the way through to the other side where you can put a nut and washer on each end.
I agree that the stud is anchored on the other side of the case and you can see that by the bulge on the other side and only one side of the case allows for a nut and washer.
In reference to the torque value I was thinking ahead, to when I do the patch I need to torque the stud into the case and then I need to torque the nut on the stud. Or do I not need to worry about torque, just snug it down?
Thanks again for all the help, I just want to get this right.

If OP were to undertake replacing the stud, how exactly would he remove the existing stud?
What do you grab and turn it with?