Off Topic Again - Nord Lock Washers Slipping on Exhaust Manifold Bolts

[dansawyer]

This is the opposite of a recent post. I have put the manifold back on, torqued and tested with no leaks. I used Nord Lock washers to hold the bolts in place, this may be the issue. The theory is they will bite into the manifold and the bolt and the wedge lock design is supposed to prevent them working themselves loose. The problem is the Nord Lock bolt combination is not holding, the bolts are working loose. I also used a small amount of anti - sieze on the bolts.

The vehicle is a Cat 3126, the manifold is cast iron, and the bolts are a black stainless steel. I re-torqued the bolts to spec thinking that was just the gasket setting in. I cycled it again up to about 150 degrees F and the bolts needed about 1/15 turn to be back in spec. I then drove the vehicle about 12 miles, this was a full heat cycle up to operating temp for 15 minutes or so. Today the bolts were way loose, I had to torque them over 1/6 turn to get back to spec.

Question: Is there something about the cast and stainless being too hard for the Nord Lock to sink into the manifold / bolts? The torque is only 30 ft lb, this may be too low for the washers to work?

I thought and thought the washers were bi directional, they were independent of which side was up. Did I over think this?

I can remove 11 of the 12 bolts one at a time am remove the Nord Locks. The original bolts were held fast. I am thinking that this may be required.

Again, thank you all in advance.

PS The engine runs great and is quiet with the new gaskets. With the bolts working loose this is only temporary.

 

[dansawyer]

Follow up: I could use a dimple tool to mark a bolt and see if rotating?
I could also remove the Nord Lock from say 2 bolts and see if they stayed in place.

 

[Nutfarmer]

You might try and center punch the nut and the threaded stud after torquing them down. It will deform the nut and thread enough to lock in place , yet still permit removal.

 

[dansawyer]

Thank you. It is a bolt. I could switch to studs and then do the above. Or I could try to add a dimple between the head and the manifold. That would be less effective than if it were a stud. I will experiment.

 

[dansawyer]

I just re-checked all the bolts. They had all worked loose to about 1/6 of a turn. I also checked 2 of the nuts holding the turbocharger to the manifold, they were secure. They were still torqued correctly.
Based on the above I plan to remove 6 of the 12 bolts, one at a time, remove the nord lock, and reinstall dry to the proper torque. As part of a general shake down for a 2500 mile trip the plan is a 50 mile test run. I will report back the findings.

 

[benmychree]

What were the OEM recommendations for the installations; I'd think that they would be the best route to success.

 

[Jake M]

Those bolts are not something that's prone to working loose. Extra security is not required.

Nord Locks, as I'm sure you can see, use a ramp and wedge in the middle. They require enough torque to A) print the outside ridges of the two washers into the parent metals so that they get a solid hold, and B) enough torque to STRETCH the bolt, such that once the two halves of the washer start to follow the bolt/manifold, and the ramps ratchet over themselves, each time it drops into a "notch" and relieves some of the stretch, there still needs to be enough stretch remaining to maintain the proper clamp load.

In your application, you do not have enough factory torque or factory designed clamp load to make the Nord Locks work properly.

In my experience, while you CAN find "torque adjustments" to use a Nord-Lock in some lighter applications like this, it's still a sketchy, hit and miss proposition. Nord Locks do not like torque wrenches. They're really best at worn out, wallered out stuff where torque is out the window, and you're gonna crank stuff together to within an inch of it's life. They're kind of magic in that sort of last ditch effort, but not so much for general maintenance.

I know you're trying to do whatever you can to never have to go back there, but I would leave them out, and assemble per the manual. Almost. In fact, I WOULD use the anti-sieze that you mentioned, and I'd still "torque" them. It might be a "click elblow" torque, where I "click" the easy ones to train up my click elbow, it's not a horribly precise operation, but I wouldn't reduce for the lubricant either. In manifold bolts (and some others, but NOT universally), it's kind of a wash with the "used and aged" holes that the bolts are going into.

EDIT:
This is bugging me-

Is there something about the cast and stainless being too hard for the Nord Lock

What do you have in there that is stainless? Is it stainless Nord Locks, or did you put stainless bolts in there?

 

[pdentrem]

Safety wire but it is a bit of work to do so.
Pierre

 

[dansawyer]

The bolts are stamped as A286 alloy, it is described as a stainless steel. The specs are for 32 ft lbs; I do not believe this is sufficient for the washers to imprint. I don't know what the Nord Locks are made from, the entire design is based on being hard enough to imprint into the mating surfaces.

 

[Jake M]

The bolts are stamped as A286

Cool. That abates my biggest concern. Some grades of stainless bolts, and some unspecified stainless bolts can be made of cheese. Cheese gets weird sometimes at manifold temperatures.

The specs are for 32 ft lbs; I do not believe this is sufficient for the washers to imprint.

I would agree. Not enough to make a Nord Lock work on several levels.

I don't know what the Nord Locks are made from,

Kryptonite. They are HARD. Hardened zinc plated carbon steel or hardened stainless, either way.

the entire design is based on being hard enough to imprint into the mating surfaces.

I disagree a little. Half of the design is based on that. The other half of the design is having enough length of unengaged bolt/stud to allow enough elongation, at a reasonable torque, to allow the ratchets between the washer halves to ratchet, and enough torque to cause the ratchets to ratchet. That's a significant axial distance to get one ramp over the other ramp.

I'm not sure how the elongation in these bolts works out. I would NOT recommend this lightly, and please consider before going there how well your spidey sense is trained where tightening things is concerned, but if you're having a problem... (and you are having a problem....), the bolts you selected (assuming they're from a reputable place) should be easily qualified for a higher torque than what you're at. In theory they'd take 50 pounds, in practice, especially considering you mentioned a dab of anti-seize, I'd cap that notion at about 40 pounds, but maybe it comes to that. The bolts "could" be in jeopardy there, but the cylinder head it's self- That's stout. If your bolts are the same length (same engagement as the originals), you won't be jeopardizing the cylinder head, just the bolts. And according to the spec's (which I can't verify as I didn't select the bolts), the bolts "should" be fine with that. that "may" be enough to impart the stretch needed to get the nord locks over the hump (where the torque wrench will inevitebly "click", and still have enough preload after the washer lands in a locked position.