Exhaust nuts backing off - options?

[Kenny_Z]

I've got an aftermarket exhaust on Red. The last time I drove her the exhaust sounded off after the engine warmed up a bit. It sounded exactly like an exhaust leak. The next day I checked the system. None of the studs had issues but some of the nuts were tight, one I could spin with a single finger, and others were loose but needed a wrench to tighten. Strangely enough the nuts that backed off the most were the ones I could easily get my torque wrench on so I know they were set right. They all had blue locktight. I'm thinking of stepping up to the red.

If I recall correctly our exhaust studs are 7mm and I can't find a flange locking kit that goes below 8mm. Even kits made especially for imports and turbos don't go below 8mm. I expect a nylon lock nut to just melt and be useless. Any other options we have short of drilling and safety wire?

[David T]

I've got an aftermarket exhaust on Red. The last time I drove her the exhaust sounded off after the engine warmed up a bit. It sounded exactly like an exhaust leak. The next day I checked the system. None of the studs had issues but some of the nuts were tight, one I could spin with a single finger, and others were loose but needed a wrench to tighten. Strangely enough the nuts that backed off the most were the ones I could easily get my torque wrench on so I know they were set right. They all had blue locktight. I'm thinking of stepping up to the red.

If I recall correctly our exhaust studs are 7mm and I can't find a flange locking kit that goes below 8mm. Even kits made especially for imports and turbos don't go below 8mm. I expect a nylon lock nut to just melt and be useless. Any other options we have short of drilling and safety wire?

Locktite won't work with the high temps. Try using 2 nuts per, one to hold the manifold and one to lock the 1st nut.

[Bitsyncmaster]

There also are nuts that are self locking. What they do is punch a little dimple into the nut so the threads keep pressure on the stud. Maybe a split ring lock washer would help.

[Rich]

There also are nuts that are self locking.

Often called top locknuts. Intentionally-deformed upper threads. No plastic in them. Like these shown here in M7 size:
LINK: http://www.homedepot.com/p/Everbilt-M7-1-0-Zinc-Plated-Tension-Lock-Nut-43608/202209726# (http://www.homedepot.com/p/Everbilt-M7-1-0-Zinc-Plated-Tension-Lock-Nut-43608/202209726#)

The flange locknuts are OK for sheet metal and shelving and such. Not for high-temp jobs like this.

[DMC5180]

I use M7 Split lock washers between the nut and flat washer. Loosening is NOT an Issue.

[Kenny_Z]

I have the split lock nut washers on there but it didn't help. I'll give those tension lock nuts a try. If that fails I'll double up the nuts. That wasn't my first choice because it's hard enough to get one wrench in there.

[LEVY]

You need to use something that can be easily removed few years later if need it, try this lock nut:

24358

http://www.thb-inc.net/flex-lock-nut.html

LEVY

[DMC5180]

Often called top locknuts. Intentionally-deformed upper threads. No plastic in them. Like these shown here in M7 size:
LINK: http://www.homedepot.com/p/Everbilt-M7-1-0-Zinc-Plated-Tension-Lock-Nut-43608/202209726# (http://www.homedepot.com/p/Everbilt-M7-1-0-Zinc-Plated-Tension-Lock-Nut-43608/202209726#)

The flange locknuts are OK for sheet metal and shelving and such. Not for high-temp jobs like this.

I'm surprised these are even available. M7 stuff is really hard to come by. we are lucky to have regular nuts let alone that kind of Self locking type.

Either way self locking nuts should not be needed in this application, if torqued properly.

All of the STUD/NUT kits available rely on Plain Nuts.