Dundertaker

I wanted to share my experience with NORD-LOCK Washers: I've got two S3s that have had the Manifold to X-pipe nuts come loose. On the 85, this caused an exhaust leak. I called HANS, and we workshopped some solutions. He suggested STAGE8.com as an option. When reviewing them, they're not big on METRIC, and everything is 1 1/2" long, etc... Plus, I wasn't sure if they'd fit and hold (They should have). So I investigated other LOCKING systems and found NORD-LOCK Washers. I found this test video, and they make them in almost every size we use on a 928. This video should answer almost every question. The big one is YES, they're reusable, you just have to overcome the tension by a few lbs over spec torque for them to break loose.


The basic premise is "Mechanical grip" once the bolt is under tension. It uses teeth and cams to hold the bolt or, with two washers, the bolt and the nut. They're designed for high-vibration environments, and one could assume a SILKY SMOOTH Porsche V8 wouldn't be a problem. I've used them for the Manifold to X-Pipe Flange and the REAR FLEX PLATE RIVET FIX so far. I had the Trans and TT out for Bearings and leak fixes...Constantine suggested I send him a picture of my rear flex plate and the tell tail signs (Rust fingers) that were there, and he suggested WYIT. I should find the Porsche Service Bulletin and replace the Rivets. They worked great, and I am very confident they will not come loose like a spring/lock washer would have. The evidence for these being a good option and my first-hand experience after driving the car a few thousand miles I felt compelled to share this with the group.

Dundertaker

Link to the Flex Plate bulletin from Porsche..I did Red LocTite the nuts for a "belt and suspenders": https://rennlist.com/forums/928-foru...l#post10718903

Jim M.

That looks like a great system, but from my aircraft maintenance training your bolts are too short. You don't have full engagement of the nut. The bolt should protrude beyond the top of the nut, yours aren't even flush. Do you need the washers under both the bolt head and the nut? I'm no engineer, but I think you have reduced the grip strength of the nut by not fully engaging all of the threads.

Rob Edwards

So they're analogous to the ribbed ('Verbus-Rib') connecting rod nuts. I like it.

Dundertaker

They are past the nut, but agree, not by much. The instructions call for both sides in a nut and bolt application and only the bolt side if it's a threaded hole, etc. otherwise the bolt could spin loose.

I also, as noted, red loctited them.

D

Dundertaker

I've seen similar systems with subtle differences. I'm sure they all are "special" in their own way.... These are about $.40-.80 cents each vs $$$ for some of the race stuff. You also can use the OEM bolt and nut. The clip style systems you can't.

D

Kevin in Atlanta

6mm version is used to secure the Bearing Bracket to the torque tube. NLA from Porsche.

Scott Peterson

I'm just wondering what is wrong with stover nuts. They have exceptional anti-vibration and on exhaust parts I use the copper coated ones from Bel-Metric.com

Dundertaker

You're welcome to come to TN and try and find the ones that fell off to inspect them. I've used the stock system, the "stover" nuts, Nylocs, and even double nut with a spring lock washer, etc... If you watch the video, you can see the evidence for yourself as to "what's wrong with..." multiple different types of fasteners. I"m sharing a possible solution for an age-old problem of fasteners that don't hold their torque. I'm 2 for 2 with having an issue with the Exhaust manifold bolts coming loose and causing a leak, this was the solution.

Bulvot

I have over 23 years of experience using NordLock washers on another vehicle. They are primarily used to keep bolts from backing out that secure the axles to the differential output flanges. Commonly accepted installation technique is to use a generous amount of red loctite in combination with the nordlock washers.

Here are my lessons learned:

1) Do not, unless there are absolutely zero other options and/or it's an emergency, reuse nordlock washers. They do not hold as well after their first use. And if you install a set and then decide to back the bolt out for some reason immediately after installation...put on a new nordlock.
2) The bolts and the threads they are installed into (whether flange or nut) must be in like new condition. After repeated use, they must be replaced. The metal stretches, galls and otherwise is less than ideal, and any less than ideal material conditions will result in the nordlock being unable to hold the bolt in place.
3) Nordlocks are superior to lock washers.
4) The only thing better than nordlocks are the above referenced locking tabs that secure the bolt against a neighboring bolt.
5) The nordlocks that come pre-bonded to each other are the easiest to use since there is no thinking involved or explanation to someone else using them, just put them on. (installing them backward isn't much better than using regular flat washers).

In the application that I have this experience with, it is very common for the bolts to back out if the above aren't observed. If you over torque a bolt by even a little...throw it out and preferably the nut/flange as well. Forget to put red loctite on and then undo the bolt so you can add it...throw out the nordlock washers. I regularly replace the flanges after several bolt installation cycles, and replace the bolts even more frequently. Since doing those things, I haven't had any failures.

Failure to observe the above has resulted in sometimes catastrophic and spontaneous destruction of critical drivetrain and braking components on mine and many others' vehicles of the same type. It's so common that there are well known sounds that new owners are advised to listen for and how to address them before catastrophic failure.

I don't say this to disparage the nordlocks, They are superior to almost anything else other than the locking tabs. But, they are not a panacea. They should not be reused, no matter what the manufacturer might claim, and the bolts/nuts/receiving-threads should be replaced regularly (every time if that's an option). They don't do well with any amount of stretching or loosening. And red loctite is a wise addition.

Keep in mind that the above lessons are learned in situations and uses that probably far exceed anything the original poster will put the nordlocks through. But adherence to the above will achieve the best possible results.

With respect to thread engagement, SAE spec for steel is 1.0 to 1.5 times the diameter of the bolt. For example, a 15mm bolt requires 15mm to 22mm of thread engagement. I prefer protrusion of the bolt past the last of the nut threads, but I've gone flush with the nut threads before without issue. Just consult an SAE thread engagement chart, or use the 1.5x rule of thumb, and you'll be fine.

Dundertaker

Thank you...this adds TONS of good information and makes the thread even more valuable. Hopefully it helps someone.

I also agree the mechanical lockers like "Stage8" are even a step above and give you a visual when you inspect "it's still locked"...which in racing and some "mere mortals" applications could be valuable.

The cost and ease of use makes these a winner for most applications and I have limited experience...exactly 15 bolts worth....you obviously have more. Thanks again for the excellent contribution.

Dundertaker

DHS928

Would you use them for a head gasket change? After watching the video I wonder how long it takes for the head nuts to loosen.